Plant-based production methods for culture media proteins

Abstract

The present disclosure relates to the field of methods for producing component proteins of culture media, such as transferrin, by plants More particularly, this disclosure relates to methods for producing low purity extracts of such component proteins from plants that may be used in cellular agriculture.

Description

[0001]Plant-based production methods for culture media proteins Cross-reference to related applications The present application claims priority from Australian Provisional Patent Application No. 2023902612 filed on 17 August 2023, the contents of which are incorporated herein by reference in their entirety. Technical field The present disclosure relates to the field of methods for producing component proteins of culture media, such as transferrin, by plants. More particularly, this disclosure relates to methods for producing low purity extracts of such component proteins from plants that may be used in cellular agriculture. Background In vitro meat production is the process by which muscle or organ tissue from animals is grown in laboratories using cell culture techniques to manufacture meat and meat products. It is expected that these processes will use significantly less arable land and water and emit significantly less carbon that animal-based production. The culture media for such production processes requires components, such as amino acids, salts, vitamins and growth factors, necessary for cell proliferation. These components are generally provided by the addition of foetal bovine serum (FBS) to the media before use. As FBS is derived from unborn calves, an alternative source of these culture medium components is required to ensure that in vitro meat production is free from utilising animal products, particularly animal-derived serum. Accordingly, there remains a need for improved methods of producing component proteins, such as growth factors and serum proteins, like transferrin, for use in an animal component-free culture medium for in vitro meat production. Summary The present disclosure is based on the surprising finding that a low purity extract of transferrin obtained from plants, can be utilised to supplement a cell culture medium for in vitro meat production. In a first aspect, the present disclosure provides a method of producing a component protein, said method including the steps of: (a) providing a plant configured to express the component protein that has been cultivated under suitable conditions to express the component protein, wherein the component protein is of non-human origin; and (b) extracting a low purity extract of the component protein from the plant. In a second aspect, the present disclosure provides a method of producing a component protein for a culture media, said method including the steps of: (a) providing a plant configured to express the component protein, wherein the component protein is of non-human origin; (b) cultivating the plant under conditions and for a time sufficient to express the component protein; and (c) extracting a low purity extract of the component protein from the plant. Suitably, the component protein is present in an amount less than about 95% of a total protein content of the low purity extract. More particularly, the component protein can be present in an amount of less than about 80% of a total protein content of the low purity extract. In particular examples, the extraction step of the present methods comprises a dialysis and / or filtration step. For such examples, the dialysis and / or filtration step suitably includes dialysing and / or filtering the culture medium with a membrane having a molecular weight cut off of at least about 2.5 kDa. According to certain examples, the membrane has a molecular weight cut off of between about 5 kDa and about 15 kDa. In other examples, the membrane has a molecular weight cut off of between about 25 kDa and about 35 kDa. For some examples, the membrane has a molecular weight cut off of about 10 kDa. In other examples, the membrane has a molecular weight cut off of about 30 kDa. According to various examples, the membrane has a molecular weight cut off of about 50 kDa. Suitably, the present methods further include the step of lyophilising the low purity extract of the component protein. According to certain examples, the plant is or comprises a safflower plant, a soybean plant, a benth plant, a camelina plant or a canola plant. For particular examples, the component protein is of an origin selected from the group consisting of a non-human mammalian species, an avian species and a teleost species, such as a bovine, a chicken or a salmon. Suitably, the component protein is selected from the group consisting of transferrin, albumin, insulin, insulin-like growth factor 1 (IGF-1), insulin-like growth factor 2 (IGF-2), fibroblast growth factor 2 (FGF2) activin, transforming growth factor β (TGF-β), neuregulin 1 (NRG1) and any combination thereof. In various examples, the component protein is or comprises transferrin. In a third aspect, the present disclosure provides an isolated component protein produced according to the method of the first or second aspects. In a fourth aspect, the present disclosure relates to a low purity extract of a component protein, wherein the component protein has been produced by a plant configured to express the component protein and wherein the component protein is of non-human origin. In a fifth aspect, the present disclosure provides a kit for producing a culture medium for culturing non-human animal cells, said kit comprising a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to the non-human animal cells. Suitably, the kit further comprises a base medium. In a sixth aspect, the present disclosure provides a culture medium for culturing non-human animal cells comprising: (a) a base medium; and (b) a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to the non-human animal cells. Suitably, the culture medium is free or substantially free of serum. In a seventh aspect, the present disclosure provides a method of producing a culture medium for culturing non-human animal cells, said method including the steps of: (a) providing a base medium; (b) adding a low purity extract of a component protein to the base medium, wherein the component protein has been produced by a plant and is of a same or similar species to the non- human animal cells. In an eighth aspect, the present disclosure relates to a method of culturing non-human animal cells, said method including the step of culturing the non-human animal cells in a culture medium comprising a base medium and a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to that of the non-human animal cells. In a ninth aspect, the present disclosure provides a method of in vitro meat production, said method including the steps of: (a) providing a plurality of non-human animal cells; and (b) culturing the non-human animal cells in a culture medium comprising a base medium and a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to that of the non-human animal cells. Suitably, the methods of the eighth and ninth aspects further include the earlier step of isolating the plurality of non-human cells from an animal source. For the methods of the above two aspects, the component protein is suitably of an origin selected from the group consisting of a non-human mammal, an avian or a teleost. Referring to the methods of the eighth and ninth aspects, these may further include the step of harvesting a meat product produced from culturing the non-human animal cells. For the kit of the fifth aspect, the culture medium of the sixth aspect or the method of the seventh to ninth aspects, the low purity extract of the component protein suitably has been produced by the method of the first or second aspects. Referring to the above aspects, the component protein is suitably present in the low purity extract in an amount less than about 95% of a total protein content of the low purity extract. More particularly, the component protein can be present in the low purity extract in an amount less than about 80% of a total protein content of the low purity extract. In a tenth aspect, the present disclosure provides a meat product produced according to the method of the eighth or ninth aspects. Brief description of the drawings The following figures form part of the present specification and are included to further demonstrate certain aspects of the present disclosure. The disclosure may be better understood by reference to one or more of these figures in combination with the detailed description of specific embodiments presented herein. It will be appreciated by persons skilled in the art that numerous variations and / or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. Figure 1. The sum of the areas under the peak for the 4 most abundant MS / MS transitions of transferrin specific peptides for the construct SN750 in Benthamiana. Figure 2. Matrix matched calibration curve used for absolute quantification of transferrin produced in Benthamiana. Figure 3. Western blot of protein extracts from Benthamiana infused with the SN750 construct. Lanes 1, 2 and 3 are the total, insoluble and soluble protein fractions respectively. Figure 4. Functionality assay using C2C12 cells. Transferrin (Tfn) extracted from benth leaves was added at various concentrations (10, 20 and 40 ug / ml media) to the cell culture media and compared with cell growth in transferrin negative B9 and standard DMEM media supplemented with 10% FBS. Cells were grown for 7 days and cell numbers measured every other day. Figure 5. Alphafold model of Transferrin (TfR) with a c- and n-terminal strep tag, and the bovine transferrin receptor complex with Fe3+. Figure 6. Anti-streptactinTMWestern blot (L) and post blot Coomassie gel (R) of the SN772 purification. “T” = Total fraction “I” = input fraction, “P” = pellet fraction, “FT” = flowthrough fraction “E” = eluate fraction. Size marker is indicated on the left side of the western blot. Figure 7. C2C12 cell viability with unfiltered (left panel) and filtered (right panel) benth leaf extracts containing transferrin. Figure 8. C2C12 cell viability with unfiltered (left panel) and filtered (right panel) Camelina seed extracts containing transferrin. Figure 9. C2C12 cell growth with plant purified transferrin (SN772) measured over 9 days. The far-left column represents C2C12 cells in B9 media without any transferrin added, and the following columns represent C2C12 cells in B9 media supplemented with increasing amounts of plant transferrin (SN40-200). The final column represents C2C12 cells in B9 media with commercial transferrin added. Key to the Sequence Listing SEQ ID NO: 1 full length amino acid sequence of a bovine transferrin protein E ID 2 i i f i f i i ic SEQ ID NO: 19 tryptic peptide sequence of a bovine transferrin protein NYELLCGDNTR he General Techniques and Definitions Unless specifically defined otherwise, all technical and scientific terms used herein shall be taken to have the same meaning as commonly understood by one of ordinary skill in the art (e.g., in genomics, immunology, molecular biology, immunohistochemistry, biochemistry, oncology, and pharmacology). The present disclosure is performed without undue experimentation using, unless otherwise indicated, conventional techniques of molecular biology, microbiology, recombinant DNA technology and immunology. Such procedures are described, for example in Sambrook, Fritsch & Maniatis, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratories, New York, Fourth Edition (2012), whole of Vols I, II, and III; DNA Cloning: A Practical Approach, Vols. I and II (D. N. Glover, Second Edition., 1995), IRL Press, Oxford, whole of text; Oligonucleotide Synthesis: A Practical Approach (M. J. Gait, ed, 1984) IRL Press, Oxford, whole of text, and particularly the papers therein by Gait, ppl-22; Atkinson et al, pp35-81; Sproat et al, pp 83-115; and Wu et al, pp 135-151; 4. Nucleic Acid Hybridization: A Practical Approach (B. D. Hames & S. J. Higgins, eds., 1985) IRL Press, Oxford, whole of text; Immobilized Cells and Enzymes: A Practical Approach (1986) IRL Press, Oxford, whole of text; Perbal, B., A Practical Guide to Molecular Cloning (1984) and Methods In Enzymology (S. Colowick and N. Kaplan, eds., Academic Press, Inc.), whole of series. Those skilled in the art will appreciate that the present disclosure is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features. The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purpose of exemplification only. Functionally equivalent products, compositions and methods are clearly within the scope of the disclosure, as described herein. Each feature of any particular aspect or embodiment or embodiment of the present disclosure may be applied mutatis mutandis to any other aspect or embodiment or embodiment of the present disclosure. Throughout this specification, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e., one or more) of those steps, compositions of matter, groups of steps or group of compositions of matter. As used herein, the singular forms of “a”, “and” and “the” include plural forms of these words, unless the context clearly dictates otherwise. For example, a reference to “a bacterium” includes a plurality of such bacteria, and a reference to “an allergen” is a reference to one or more allergens. The term “and / or”, e.g., “X and / or Y” shall be understood to mean either “X and Y” or “X or Y” and shall be taken to provide explicit support for both meanings or for either meaning. Throughout this specification, the word “comprise’ or variations such as “comprises” or “comprising” will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. By “consisting essentially of”, in the context of an amino acid sequence, is meant the recited amino acid sequence together with an additional one, two or three amino acids at the N- and / or C-terminus. By “consisting essentially of”, in the context of a nucleic acid sequence, is meant the recited nucleic acid sequence together with an additional one, two or three nucleic acids at the 5’ end and / or 3’ end. The term “substantially” does not exclude “completely” (e.g., a composition which is “substantially free” from Y may be completely free from Y). Throughout the present specification, various aspects and components of the disclosure can be presented in a range format. The range format is included for convenience and should not be interpreted as an inflexible limitation on the scope of the present disclosure. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub- ranges as well as individual numerical values within that range, unless specifically indicated. For example, description of a range such as from 1 to 5 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 5, from 3 to 5 etc., as well as individual and partial numbers within the recited range, for example, 1, 2, 3, 4, 5, 5.5 and 6, unless where integers are required or implicit from context. This applies regardless of the breadth of the disclosed range. Where specific values are required, these will be indicated in the specification. The term “about” in relation to a numerical value x is optional and means, for example, any number within 1, 5 or 10% of the referenced number. In certain embodiments, the term “about” encompasses the exact number recited. All computer programs, algorithms, patent and scientific literature referred to herein is incorporated herein by reference. For the present disclosure, the database accession number or unique identifier provided herein for a gene or protein, as well as the gene and / or protein sequence or sequences associated therewith, are incorporated by reference herein. Methods of producing component proteins by plants The inventors have surprisingly shown that low purity extracts of transferrin protein of a non-human origin (e.g., bovine transferrin) produced by plants can be successfully used in culturing non-human animal cells obtained from the same species as that of the transferrin protein. Advantageously, this demonstrated functionality of low purity extracts of non-human component proteins of cell culture media can lead to improved economics for in vitro meat production, whilst also obviating the need for animal-derived components like FBS in the culture process. In one broad form, the present disclosure provides a method of producing a component protein, said method including the steps of: (a) providing a plant configured to express the component protein that has been cultivated under suitable conditions to express the component protein, wherein the component protein is of non-human origin; and (b) extracting a low purity extract of the component protein from the plant. For such examples, the method may further include the earlier step of cultivating the plant under suitable conditions to express the component protein. Accordingly, in one form, the present disclosure provides a method of producing a component protein for a culture media, said method including the steps of: (a) providing a plant configured to express the component protein, wherein the component protein is of non-human origin; (b) cultivating the plant under conditions and for a time sufficient to express the component protein; and (c) extracting a low purity extract of the component protein from the plant. In a related form, the present disclosure provides a low purity extract of a component protein, wherein the component protein has been produced by a plant configured to express the component protein and wherein the component protein is of non-human origin. In another form, the present disclosure relates to a component protein produced according to the method described herein. The term “component protein” refers to any protein, whether of chemical or biological origin, that can be used in cell culture media to maintain or promote the growth or proliferation of cells. The terms “component,” “nutrient” and ingredient” can be used interchangeably herein and are all meant to refer to such compounds. Typical ingredient proteins that are used in cell culture media include serum proteins (e.g., albumin), growth factors, carrier proteins (e.g., fetuin), extracellular matrix proteins (e.g., fibronectin) and iron transport proteins. Other ingredients that promote or maintain cultivation of cells ex vivo can be selected by those of skill in the art, in accordance with the particular need. Suitably, the component protein is selected from the group consisting of transferrin, albumin, insulin, insulin-like growth factor 1 (IGF-1), insulin-like growth factor 2 (IGF-2), fibroblast growth factor 2 (FGF2) activin, transforming growth factor β (TGF-β), neuregulin 1 (NRG1) and any combination thereof. In particular examples, the component protein is a transferrin protein. It is contemplated that the plant can be of any species, variety or strain, such as those described herein. Suitably, the plant is capable of being modified to recombinantly express (e.g., transiently express, stably express, constitutively express and / or conditionally express) the component protein. Accordingly, the present method may include the earlier or initial step of modifying, or more particularly genetically modifying, the plant to express the component protein, such as by those methods provided herein. In various examples, the plant has been configured or modified to transiently express the component protein. According to other examples, the plant has been configured or modified to stably express the component protein. In particular examples, the plant is a safflower plant, a soybean plant, a benth plant, a camelina plant or a canola plant. In order to produce the recombinant component protein, the plant is suitably cultivated or grown under conditions and for a time period that allow or are appropriate for expression of said component protein. In various examples, extraction of the low purity extract of the component protein can be performed following harvesting of a plant part, such as leaves, seeds and / or fruit, from the respective plant, particularly in those examples in which the component protein is produced, such as selectively produced, within the plant part in question. Accordingly, the present methods may include the step of harvesting a plant part from the plant. Extraction may then be performed in respect of the plant part harvested from the plant. The term “plant part” refers to any part of a plant including but not limited to the embryo, fruit, shoot, root, stem, seed (inclusive of grain), stipule, leaf, petal, flower bud, flower, ovule, bract, trichome, branch, petiole, internode, bark, pubescence, tiller, rhizome, frond, blade, ovule, pollen, stamen, and the like. In particular examples, the plant part harvested from the plant is or comprises one or more seeds. In other examples, the plant part harvested from the plant is or comprises one or more leaves. In other examples, the plant part harvested from the plant is or comprises one or more fruit. Suitably, the plant or plant part is harvested at a time after transfection, such as transient transfection, of the plant that is sufficient to allow for expression of the component protein therein. In particular examples, the plant or plant part is harvested at least about 1 day (e.g., at least about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 days or any range therein) after transfection of the plant. For some examples, the plant or plant part is harvested about 1 day to about 30 days, about 2 days to about 20 days, about 3 days to about 15 days or about 4 days to about 10 days after transfection of the plant. The plant may also be of any suitable age at the time of harvesting plant parts and / or component protein extraction therefrom. In particular examples of the methods provided herein, the extraction step includes initially extracting a substantially unpurified or crude extract that includes the component protein (e.g., transferrin protein and optionally other plant proteins and components) from the plant or a part thereof. The terms “crude extract” or “substantially unpurified extract” means that a composition made from the plant or part thereof has not been subjected to significant purification steps, such as chromatographic protein purification and fractionation steps. The crude extract may be considered to include a total protein content or total soluble protein content of the plant or part thereof (e.g., the total amount of protein that may reasonably be extracted from the plant or part thereof using standard methods). For such examples, cells of the plant and / or plant part are suitably lysed before recovering or isolating the crude extract therefrom. The plant cells may be lysed biologically, such as by contacting them with an enzyme able to digest their cell walls (e.g., a cellulase, a ligninase). Alternatively or additionally, the plant cells may be lysed mechanically, by breaking their cell walls, such as by using a press, vortex, a bead beater or sonicator, or lysed chemically, such as by osmotic shock, acid treatment or alkali treatment. Once lysed, the plant or part thereof may be contacted with a suitable solvent or buffer (e.g., Tris-HCl) so as to dissolve the crude extract therein. The component protein present in the crude extract can then be further extracted or purified, such as by those methods provided herein, to generate, for example, a low purity extract thereof. During extraction of the crude extract and / or the low purity extract, the plant cells and / or lysed debris thereof may be separated, isolated or purified from the crude extract and / or low purity extract by standard methods like centrifugation, separation, filtration or ultrafiltration. The component proteins produced therefrom can then be concentrated and / or purified according to methods known to those skilled in the art, such as dialysis, gradient ultracentrifugation (GUC), filtration, precipitation (e.g., “salting out”), chromatography, column purification, non- chromatographic purification tags (e.g., streptavidin, an elastin-based or cellulose binding domain containing tag, optionally with a self-cleaving option, such as an intein-based tag), column-based purification (e.g., column comprising Fe2+to bind transferrin), magnetic particle purification (e.g., purification of Fe2+-bound transferrin), buffer exchange and any combination thereof. Other plant components or contaminants, such as sugars, starches, carbohydrates, lipids and the like, present in the crude extract and / or the low purity extract, may be removed by enzyme (e.g., amylase, lipase, sucrase, isomaltase) treatment thereof. Suitably, the crude extract and / or the low purity extract can be subjected to a sterilisation step. Such a sterilisation step may be performed by any means known in the art, including, but not limited to, passage of the crude extract and / or the low purity extract through a sterilisation filter of sufficient size (e.g., about 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3 μm or any range therein) to remove one or more microbes therefrom. According to particular examples, the low purity extract of the component protein is isolated or extracted from the plant or part thereof, such as from a crude extract thereof, by dialysis and / or filtration. More particularly, the component protein can be isolated or extracted from the plant or part thereof by dialysis. In other examples, the component protein is isolated or extracted from the plant or part thereof by filtration. For particular examples, the component protein is isolated or extracted from the plant or part thereof by dialysis and filtration. In such examples, a centrifugation step may be performed before or after dialysis and / or filtration or between filtration and dialysis irrespective of their order. As used herein, the term “filtration” refers to a process of separating particulate matter from a fluid, such as a crude extract of the plant or part thereof, by passing the fluid through a medium or membrane that will not pass the particulates. As used herein, the term “dialysis” refers to a form of filtration, or a process of selective diffusion through a membrane (e.g., a dialysis membrane). Dialysis is typically used to separate low-molecular weight solutes that diffuse through the membrane from high-molecular weight solutes which do not. For example, a feed of fluid can be passed over a semipermeable membrane or filter, and a feed of dialysate is passed over the other side of that membrane or filter, and then there is diffusive and selective transport of dissolved solutes, typically below a particular molecular weight, between the fluids. The composition of one fluid, the dialysate, may be used to deplete the composition of the other fluid, the feed fluid, of some molecule or molecules. By extension, the dialysate may be used to concentrate particular molecules, particularly those of a high molecular weight within the feed fluid (e.g., a transferrin protein). Suitable membranes for dialysis and filtration methods are commercially available and include, for example, cellulose acetate, regenerated cellulose, polyester and cellulose ester. Commercially available dialysis kits are also known in the art (see, e.g., Slide-A-Lyzer Dialysis Flasks from ThermoFisher Scientific). It is also envisaged that the dialysis time may vary depending on the dialysis membrane used, the solvent used, and the target compound. As such, optimal dialysis or filtration conditions for the extraction step herein can be selected or determined by measuring dialysis times and dialysis rates in advance. In particular examples, however, the filtration or dialysis step is conducted for a period of time of about 1 hour to about 48 hours (e.g., about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 hours or any range therein). In particular examples, the filtration or dialysis step is conducted for a period of time of about 12 hours to about 36 hours, more particularly about 16 hours to about 30 hours or even more particularly about 18 hours to about 24 hours. The separation characteristic determined by the pore size-range of a dialysis membrane or a filtration membrane is most often referred to as the molecular weight-cut off (MWCO) of the membrane. Traditionally, a membrane’s MWCO refers to the smallest average molecular mass of a standard molecule that will not effectively diffuse across the membrane. Typically, the smallest size globular macromolecule (in Daltons) that is retained by greater than 90% upon extended dialysis (e.g., greater than 8-12 hours) defines the nominal MWCO. Thus, a dialysis membrane or a filtration membrane with a 10 kDa MWCO will generally retain proteins having a molecular mass of at least 10 kDa. According to certain examples, the dialysis and / or filtration step includes dialysing and / or filtering an extract, such as a crude extract, of the plant or part thereof with a membrane having a MWCO of at least about 2 kDa (e.g., at least about 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70 kDa or any range therein). More particularly, the membrane can have a MWCO of at least about 2.5 kDa, even more particularly, at least about 5 kDa or still even more particularly, at least about 10 kDa. For particular examples, the membrane has a MWCO of between about 2 kDa and about 40 kDa. In some examples, the membrane has a MWCO of between about 2 kDa and about 20 kDa. In other examples, the membrane has a MWCO of between about 5 kDa and about 15 kDa. For various examples, the membrane has a MWCO of between about 8 kDa and about 12 kDa. According to particular examples, the membrane has a MWCO of about 10 kDa. In some examples, the membrane has a MWCO of between about 20 kDa and about 40 kDa. In other examples, the membrane has a MWCO of between about 25 kDa and about 35 kDa. For various examples, the membrane has a MWCO of between about 28 kDa and about 32 kDa. According to particular examples, the membrane has a MWCO of about 30 kDa. Referring to some examples, the dialysis and / or filtration step includes: (i) dialysing an extract, such as a crude extract, of the plant or part thereof with a membrane having a MWCO of between about 5 kDa and about 15 kDa, or more particularly about 10 kDa, to produce a first extract of the component protein; and (ii) filtering the first extract with a membrane having a MWCO of between about 5 kDa and about 15 kDa, or more particularly about 10 kDa, to produce the low purity extract of the component protein. In other examples, the dialysis and / or filtration step includes: (i) dialysing an extract, such as a crude extract, of the plant or part thereof with a membrane having a MWCO of between about 5 kDa and about 15 kDa, or more particularly about 10 kDa, to produce a first extract of the component protein; and (ii) filtering the first extract with a membrane having a MWCO of between about 25 kDa and about 35 kDa, or more particularly about 30 kDa, to produce the low purity extract of the component protein. For the above examples, the dialysis and / or filtration step may further include a centrifugation step before, between and / or after, or more particularly between, steps (i) and (ii). Moreover, for such examples, the dialysis and / or filtration step may further include a lyophilisation step before, between and / or after, or more particularly between, steps (i) and (ii). By way of example, the extract may be lyophilised prior to step (i), the first extract may be lyophilised prior to step (ii) and / or the low purity extract may be lyophilised after step (ii). Further, the extract may be centrifuged prior to step (i), the first extract may be centrifuged prior to step (ii) and / or the low purity extract may be centrifuged after step (ii). According to certain examples, the extraction step (i.e., the step of extracting the low purity extract) described herein includes a buffer exchange step, such as to remove one or more contaminating proteins or molecules from the low purity extract. In this regard, an extract, such as a crude extract, of the plant or part thereof may be contacted with a buffer exchange membrane or column. For such examples, the buffer exchange membrane or column has a MWCO of between about 2 kDa and about 20 kDa (e.g., about 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 kDa, or any range therein), more particularly between about 2 kDa and about 15 kDa, even more particularly between about 3 kDa and about 10 kDa, yet even more particularly between about 3 kDa and about 7 kDa or still even more particularly about 5 kDa. Such a buffer exchange step may be performed in addition to the dialysis and / or filtration steps disclosed herein or may be performed as an alternative means or method of purifying an extract of the plant or part thereof expressing the component protein to generate a low purity extract thereof. The terms “lowly purified” and “low purity” are intended to mean an extract, isolate or product, such as a protein extract (e.g., a low purity extract or a crude extract), in which a component protein, such as a transferrin protein, is present in an amount less than 100% (e.g., less than about 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%, 77%, 76%, 75%, 74%, 73%, 72%, 71%, 70%, 69%, 68%, 67%, 66%, 65%, 64%, 63%, 62%, 61%, 60%, 59%, 58%, 57%, 56%, 55%, 54%, 53%, 52%, 51%, 50%, 49%, 48%, 47%, 46%, 45%, 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1% or any range therein), more particularly less than about 95%, even more particularly less than about 90%, yet even more particularly less than about 85%, still even more particularly less than about 80%, further still even more particularly less than about 75%, yet still even more particularly less than about 70%, even more particularly less than about 65%, still yet even more particularly less than about 60%, further even more particularly less than about 55% or yet still more particularly less than about 50% of a total protein content, such as a total soluble protein content, thereof. In further examples, the component protein is present in the low purity extract in an amount less than about 40% of a total protein content, such as a total soluble protein content, thereof. In various examples, the component protein is present in the low purity extract in an amount less than about 30% of a total protein content, such as a total soluble protein content, thereof. In other examples, the component protein is present in the low purity extract in an amount less than about 20% of a total protein content, such as a total soluble protein content, thereof. In certain examples, the component protein is present in the low purity extract in an amount less than about 10% of a total protein content, such as a total soluble protein content, thereof. In particular examples, the component protein is present in an amount of about 5% to about 95% (e.g., about 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or any range therein) of a total protein content of the low purity extract. For certain examples, the component protein is present in an amount of about 10% to about 80% of a total protein content of the low purity extract. In other examples, the component protein is present in an amount of about 65% to about 90% of a total protein content of the low purity extract. According to various examples, the component protein is present in an amount of about 70% to about 80% of a total protein content of the low purity extract. For certain examples, the component protein is present in an amount of about 20% to about 60% of a total protein content of the low purity extract. In other examples, the component protein is present in an amount of about 30% to about 50% of a total protein content of the low purity extract. According to some examples, the component protein is present in an amount of about 35% to about 45% of a total protein content of the low purity extract. For some examples, the component protein is present in an amount of about 1% to about 30%, more particularly about 2% to about 25%, even more particularly about 3% to about 20%, yet even more particularly about 4% to about 15% or still even more particularly about 5% to about 10% of a total protein content of the low purity extract. According to some examples, the component protein is present in an amount of about 1% to about 95% (e.g., about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or any range therein) by weight of the low purity extract, such as a lyophilised form or a dry form thereof. For certain examples, the component protein is present in an amount of about 10% to about 80% by weight of the low purity extract. In other examples, the component protein is present in an amount of about 65% to about 90% by weight of the low purity extract. According to various examples, the component protein is present in an amount of about 70% to about 80% by weight of the low purity extract. For certain examples, the component protein is present in an amount of about 20% to about 60% by weight of the low purity extract. In other examples, the component protein is present in an amount of about 30% to about 50% by weight of the low purity extract. According to some examples, the component protein is present in an amount of about 35% to about 45% by weight of the low purity extract. In various examples, the component protein is present in an amount of about 8% to about 40% by weight of the low purity extract. According to particular examples, the component protein is present in an amount of about 5% to about 50% by weight of the low purity extract. For some examples, the component protein is present in an amount of about 1% to about 30%, more particularly about 2% to about 25%, even more particularly about 3% to about 20%, yet even more particularly about 4% to about 15% or still even more particularly about 5% to about 10% by weight of the low purity extract. With respect to assessing yield and / or purity of the component protein (e.g., a transferrin protein), this may be performed by any method or means known in the art. Yield of the component protein, such as in the crude extract or the low purity extract, may be measured by any means of protein quantification known in the art, such as by gel electrophoresis (e.g., Western Blot); by ELISA, or by chromatographic methods, such as HPLC (high performance liquid chromatograph), HPLC-UV or mass spectrometry methods, such as LC-MS (Liquid Chromatography-Mass Spectrometry) and LC-MRM-MS (Liquid Chromatography-Multiple Reaction Monitoring-Mass Spectrometry). In particular examples, yield of the component protein in the low purity extract is measured by LC-MS or LC-MRM-MS. In view of the foregoing and in certain examples, a MRM assay is used which employs specific peptides (such as shown in Figure 1; e.g., SEQ ID NOs: 18 to 21 of a transferrin protein) and their fragments (transitions) as discriminators of the component protein and / or indicators of an expression level thereof. In principle, any unique peptide derived from a component protein can be used to determine the amount or expression level of said component protein in a sample or extract using an MRM assay. Further to the above, a level of purity of the component protein may be determined for the present method. To this end, an extract or isolate containing the component protein will typically include impurities or contaminating proteins (e.g., non-component proteins, or more particularly non-transferrin proteins), such as host cell proteins derived from the plant cells. Purity of the component protein in the low purity extract may be measured by any means known in the art. Exemplary methods may include calculating a ratio of a level, content or concentration of the component protein, such as determined by those methods described above, in the low purity extract to a total protein content thereof. The total protein content can be assessed, for example, by a bichinonic acid (BCA) assay, gel electrophoresis, a Bradford assay, SDS-PAGE and Western Blot, or Coomassie Stain; by ELISA; by chromatographic methods, such as HPLC; or by mass spectrometry (e.g., shot-gun proteomics) methods. In particular examples, the purity of the low purity extract is determined by the ratio of a level, concentration or content of a component protein therein to a total protein content therein. For such examples, the level of the component protein is suitably measured by LC-MS or LC-MRM-MS and the total protein content is suitably measured by a Bradford assay. In other examples, the level of the component protein and total protein is suitably measured by LC-MS or LC-MRM-MS. The level of purity of the component protein in the low purity extract may then be measured by a matrix matched calibration curve. The level of purity the component protein can also be expressed as a wt% or by weight of the total protein content, such as hereinbefore described. As used herein, the terms “by weight”, “weight %” and “wt%” refer to the weight of a substance (for example, a transferrin protein) as a percentage of the weight of the composition comprising the substance or a component in the composition (e.g., the crude extract or the low purity extract). For example, the weight of a particular protein such as a transferrin protein may be determined as a percentage of the weight of the total protein content or total soluble protein content of the crude extract or the low purity extract. Once isolated, the low purity extract of the component protein may be lyophilized, so as to assist with storage and stability thereof. Methods of lyophilising protein extracts are known in the art. In particular examples, a lyoprotectant, such as hyaluronic acid, γ-cyclodextrin and / or trehalose, is used. Accordingly, the low purity extract may further comprise a lyoprotectant. In such examples, the low purity extract of the component protein can be resuspended in any suitable buffer or carrier prior to use. The buffer or carrier may be any suitable buffer or carrier known in the art. For example, the buffer or carrier may be a TRIS, acetate, glutamate, lactate, maleate, tartrate, phosphate, citrate, carbonate, glycinate, histidine, glycine, succinate, triethanolamine, or phosphate buffer. In particular examples, the lyophilised low purity extract is resuspended in PBS prior to use. Once resuspended or reconstituted in a suitable buffer or carrier, the low purity extract can be further subjected to one or more steps of centrifugation, dialysis and / or filtration as described herein, such as prior to addition to a culture medium for culturing non-human animal cells. According to various examples, the method described herein includes: (i) dialysing an extract, such as a crude extract, of the plant or part thereof, such as with a membrane having a MWCO of between about 5 kDa and about 15 kDa, or more particularly about 10 kDa, to produce a low purity extract of the component protein; and (ii) lyophilising the low purity extract. For such examples, the low purity extract may be reconstituted in an appropriate buffer or carrier, such as those described herein, prior to addition to the culture medium. Referring to some examples, the method described herein includes: (i) dialysing an extract, such as a crude extract, of the plant or part thereof, such as with a membrane having a MWCO of between about 5 kDa and about 15 kDa, or more particularly about 10 kDa, to produce a first extract of the component protein; (ii) lyophilising the first extract; (iii) reconstituting the lyophilised form of the first extract in a carrier or buffer; (iv) optionally centrifuging the reconstituted form of the first extract; and (v) optionally, filtering the first extract of step (iii) or (iv), such as with a membrane having a MWCO of between about 5 kDa and about 15 kDa, or more particularly about 10 kDa, to produce the low purity extract of the component protein. In other examples, the method described herein includes: (i) dialysing an extract, such as a crude extract, of the plant or part thereof, such as with a membrane having a MWCO of between about 5 kDa and about 15 kDa, or more particularly about 10 kDa, to produce a first extract of the component protein; (ii) lyophilising the first extract; (iii) reconstituting the lyophilised form of the first extract in a carrier or buffer; (iv) optionally centrifuging the reconstituted form of the first extract; and (v) optionally, filtering the first extract of step (iii) or (iv), such as with a membrane having a MWCO of between about 25 kDa and about 35 kDa, or more particularly about 30 kDa, to produce the low purity extract of the component protein. Non-human transferrin According to certain examples, the component protein described herein is a transferrin protein. Thus, in one form, the present disclosure provides a method of producing a transferrin protein, said method including the steps of: (a) providing a plant configured to express the transferrin protein, wherein the transferrin protein is of non-human origin; (b) cultivating the plant under conditions and for a time sufficient to express the transferrin protein; and (c) extracting a low purity extract of the transferrin protein from the plant. Transferrin is an approximately 80 kDa glycoprotein which binds to Fe3+ions and is intimately involved in iron metabolism. In this regard, serum transferrin belongs to a family of iron-binding proteins that is involved in iron transport / metabolism in the body and can be used as an additive in media for animal cell culture. Transferrin contains two domains, namely the N-lobe and the C-lobe. It is typically synthesized as an immature protein having a secretion signal peptide at its N-terminal end and is then secreted out of the cell as a mature glycoprotein having the secretion signal peptide cleaved. The transferrin protein of the present disclosure may be any natural transferrin protein, or a modified or variant version thereof (e.g., transferrin-like proteins, transferrin analogues etc as are known in the art), derived from any non-human animal species. It is envisaged, however, that such modified or variant versions of the transferrin protein suitably do not comprise or consist of a naturally occurring, native or wildtype human transferrin protein. Exemplary transferrin proteins include blood serotransferrin (also referred to as siderophilin), lactotransferrin (lactoferrin), milk transferrin, egg white ovotransferrin (conalbumin) and membrane-associated melanotransferrin. Suitably, the transferrin protein is derived from a non-primate animal species. For some examples, the transferrin protein is derived from a livestock species, such as domestic cattle, pigs, sheep, goats, camels, water buffalo, rabbits and the like. Alternatively, the transferrin protein can be derived from poultry, such as domestic chicken, turkeys, ducks, geese, pigeons and the like. According to certain examples, the transferrin protein is derived from a game species, such as wild deer, gallinaceous fowl, waterfowl, hare, rabbit and the like. In other examples, the transferrin protein (inclusive of transferrin-like proteins, variants and analogues thereof) is derived from an aquatic species or semi-aquatic species, such as fish, crustaceans, molluscs, cephalopods, cetaceans, crocodilians, turtles, frogs and the like. Suitably, the transferrin protein, inclusive of functional variants, derivatives and fragments thereof, is derived from a mammal, and more particularly a mammalian livestock species, such as cattle, pigs, sheep, goats, horse, chickens, deer and rabbit. In certain examples, the transferrin protein is derived from a bovine animal. In other examples, the transferrin protein is derived from a porcine animal. As used herein, “bovines” are members of the mammalian sub-family Bovinae and include cattle, buffalo, bison and yaks. Cattle include all breeds and sub-species of the genus Bos, including Bos indicus and Bos taurus and hybrids thereof. The nucleotide and protein sequences of bovine transferrin are publicly available (e.g., Q29443 and NM_177484.3). An exemplary amino acid sequence is set forth in SEQ ID NOs: 1 and 2. Thus, the transferrin amino acid sequence may be a protein which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO: 1 or SEQ ID NO: 2 or a fragment or derivative thereof. An exemplary encoding nucleotide sequence which has been codon optimised for expression in plants is set forth in SEQ ID NO: 3. Thus, the encoding nucleotide sequence of transferrin may be a nucleic acid which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO: 3 or a fragment or derivative thereof. Full length Bovine transferrin protein sequence (SEQ ID NO: 1) MRPAVRALLACAVLGLCLADPERTVRWCTISTHEANKCASFRENVLRILESGPFVSCVKK TSHMDCIKAISNNEADAVTLDGGLVYEAGLKPNNLKPVVAEFHGTKDNPQTHYYAVAVVK KDTDFKLNELRGKKSCHTGLGRSAGWNIPMAKLYKELPDPQESIQRAAANFFSASCVPCA DQSSFPKLCQLCAGKGTDKCACSNHEPYFGYSGAFKCLMEGAGDVAFVKHSTVFDNLPNP EDRKNYELLCGDNTRKSVDDYQECYLAMVPSHAVVARTVGGKEDVIWELLNHAQEHFGKD KPDNFQLFQSPHGKDLLFKDSADGFLKIPSKMDFELYLGYEYVTALQNLRESKPPDSSKD ECMVKWCAIGHQERTKCDRWSGFSGGAIECETAENTEECIAKIMKGEADAMSLDGGYLYI AGKCGLVPVLAENYKTEGESCKNTPEKGYLAVAVVKTSDANINWNNLKDKKSCHTAVDRT AGWNIPMGLLYSKINNCKFDEFFSAGCAPGSPRNSSLCALCIGSEKGTGKECVPNSNERY YGYTGAFRCLVEKGDVAFVKDQTVIQNTDGNNNEAWAKNLKKENFEVLCKDGTRKPVTDA ENCHLARGPNHAVVSRKDKATCVEKILNKQQDDFGKSVTDCTSNFCLFQSNSKDLLFRDD TKCLASIAKKTYDSYLGDDYVRAMTNLRQCSTSKLLEACTFHKP Mature Bovine transferrin protein sequence (SEQ ID NO: 2) DPERTVRWCTISTHEANKCASFRENVLRILESGPFVSCVKK TSHMDCIKAISNNEADAVTLDGGLVYEAGLKPNNLKPVVAEFHGTKDNPQTHYYAVAVVK KDTDFKLNELRGKKSCHTGLGRSAGWNIPMAKLYKELPDPQESIQRAAANFFSASCVPCA DQSSFPKLCQLCAGKGTDKCACSNHEPYFGYSGAFKCLMEGAGDVAFVKHSTVFDNLPNP EDRKNYELLCGDNTRKSVDDYQECYLAMVPSHAVVARTVGGKEDVIWELLNHAQEHFGKD KPDNFQLFQSPHGKDLLFKDSADGFLKIPSKMDFELYLGYEYVTALQNLRESKPPDSSKD ECMVKWCAIGHQERTKCDRWSGFSGGAIECETAENTEECIAKIMKGEADAMSLDGGYLYI AGKCGLVPVLAENYKTEGESCKNTPEKGYLAVAVVKTSDANINWNNLKDKKSCHTAVDRT AGWNIPMGLLYSKINNCKFDEFFSAGCAPGSPRNSSLCALCIGSEKGTGKECVPNSNERY YGYTGAFRCLVEKGDVAFVKDQTVIQNTDGNNNEAWAKNLKKENFEVLCKDGTRKPVTDA ENCHLARGPNHAVVSRKDKATCVEKILNKQQDDFGKSVTDCTSNFCLFQSNSKDLLFRDD TKCLASIAKKTYDSYLGDDYVRAMTNLRQCSTSKLLEACTFHKP Bovine transferrin nucleotide sequence (SEQ ID NO: 3) GATCCTGAGAGAACTGTTCGGTGGTGCACTATTTCTACCCACGAGGCTAACAAGTGCGCCAGCTTCAGAGAGAACGT TTTGCGGATTCTTGAGAGCGGCCCTTTCGTGTCTTGCGTGAAGAAAACTAGCCACATGGACTGCATCAAGGCCATCT CTAACAACGAGGCTGATGCTGTGACTCTGGATGGTGGTCTTGTTTACGAGGCTGGTCTGAAGCCTAACAACCTTAAG CCTGTTGTGGCTGAGTTCCACGGCACTAAGGATAATCCTCAGACTCACTACTACGCTGTGGCCGTGGTTAAGAAGGA TACCGACTTCAAGCTTAACGAGCTGCGGGGTAAGAAGTCTTGCCATACTGGTCTTGGTAGGTCCGCTGGTTGGAACA TTCCTATGGCCAAGCTGTACAAAGAGCTGCCTGATCCGCAAGAGTCTATTCAGAGAGCTGCTGCCAACTTCTTCAGC GCTTCTTGTGTTCCTTGCGCCGACCAGTCTAGTTTCCCTAAGCTTTGTCAGCTGTGCGCTGGTAAGGGTACTGATAA GTGCGCTTGCTCTAACCACGAGCCTTACTTCGGTTACAGCGGTGCTTTCAAGTGCCTGATGGAAGGTGCTGGTGATG TGGCTTTCGTGAAGCACTCTACCGTGTTCGACAACCTGCCTAATCCTGAGGACCGGAAGAACTACGAGCTTCTGTGT GGTGATAACACCCGGAAGTCCGTGGATGATTACCAAGAGTGCTACCTGGCTATGGTGCCTTCTCATGCTGTTGTTGC TAGGACCGTTGGTGGCAAAGAGGATGTTATTTGGGAGCTGCTGAACCACGCTCAAGAGCACTTTGGAAAGGACAAGC CTGACAACTTCCAGCTGTTCCAGTCTCCTCACGGTAAGGATCTGCTGTTCAAGGATAGCGCTGATGGCTTCCTGAAG ATCCCGAGCAAGATGGATTTCGAGCTGTACCTGGGTTACGAGTACGTTACCGCTCTGCAGAACCTGAGAGAGTCTAA GCCTCCTGACAGCTCTAAGGATGAGTGCATGGTTAAGTGGTGCGCTATCGGTCATCAAGAGCGGACTAAGTGCGATA GGTGGTCTGGTTTTTCTGGCGGTGCTATTGAGTGTGAGACTGCTGAGAATACCGAAGAGTGCATTGCCAAGATCATG AAGGGCGAAGCTGACGCTATGAGCCTTGATGGTGGTTACCTGTACATTGCTGGTAAGTGCGGTCTTGTGCCTGTGCT TGCTGAGAACTATAAGACTGAGGGCGAGAGCTGCAAGAACACTCCTGAGAAGGGTTACCTTGCAGTCGCCGTTGTTA AGACCTCCGACGCTAACATCAACTGGAACAACCTGAAGGACAAGAAGAGTTGCCACACCGCTGTTGATAGAACTGCA GGCTGGAATATCCCTATGGGCCTGCTGTACTCCAAGATCAACAACTGCAAGTTCGACGAGTTCTTCTCTGCTGGTTG TGCTCCTGGTTCTCCGAGGAATTCTTCTCTTTGCGCTCTGTGCATCGGCTCTGAGAAAGGTACTGGGAAAGAGTGCG TTCCGAACAGCAATGAGAGGTACTACGGATACACTGGCGCTTTCAGATGCCTCGTGGAAAAGGGTGATGTCGCCTTC GTTAAGGATCAGACCGTGATCCAGAACACCGACGGTAACAACAATGAGGCTTGGGCCAAGAACCTGAAGAAAGAGAA CTTCGAGGTCCTGTGCAAGGACGGAACTAGAAAGCCTGTTACTGATGCCGAGAACTGCCATTTGGCTAGGGGTCCTA ATCATGCTGTGGTGAGCAGAAAGGATAAGGCTACCTGCGTTGAGAAGATCCTGAACAAGCAGCAGGATGACTTCGGC AAGTCTGTGACTGATTGCACCAGCAATTTCTGCCTCTTCCAGAGCAACTCTAAGGACCTTTTGTTCCGGGATGACAC CAAGTGCCTTGCCTCTATCGCTAAGAAAACCTACGACAGCTACCTGGGCGACGATTATGTTAGGGCTATGACCAATC TGCGGCAGTGCTCTACCTCTAAGCTTCTTGAGGCTTGCACTTTCCACAAGCCT As used herein, the term “porcine” refers to animals of the Suidae family, which include pigs, boars and warthogs. The term also refers to any pig species or strain, such as Large White, Landrace, Meishan and Minipig. The nucleotide and protein sequences of porcine transferrin are publicly available (e.g., CAQ34904.1 and NM_001244653.1). An exemplary amino acid sequence is set forth in SEQ ID NOs: 4 and 5. Thus, the transferrin amino acid sequence may be a protein which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO: 4 or SEQ ID NO: 5 or a fragment or derivative thereof. An exemplary encoding nucleotide sequence which has been codon optimised for expression in plants is set forth in SEQ ID NO: 6. Thus, the encoding nucleotide sequence of transferrin may be a nucleic acid which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO:6 or a fragment or derivative thereof. Full length Porcine transferrin protein sequence (SEQ ID NO: 4) MRLAVRALLACAVLGLSLAVAQKTVRWCTISNQEANKCSSFRENMSKAVKNGPLVSCVKKSSYLDCIKAI RDKEADAVTLDAGLVFEAGLAPYNLKPVVAEFYGQKDNPQTHYYAVAVVKKGSNFQWNQLQGKRSCHTGL GRSAGWIIPMGLLYDQLPEPRKPIEKAVASFFSSSCVPCADPVNFPKLCQQCAGKGAEKCACSNHEPYFG YAGAFNCLKEDAGDVAFVKHSTVLENLPDKADRDQYELLCRDNTRRPVDDYENCYLAQVPSHAVVARSVD GQEDSIWELLNQAQEHFGRDKSPDFQLFSSSHGKDLLFKDSANGFLRIPSKMDSSLYLGYQYVTALRNLR EEISPDSSKNECKKVRWCAIGHEETQKCDAWSINSGGKIECVSAENTEDCIAKIVKGEADAMSLDGGYIY IAGKCGLVPVLAENYKTEGENCVNTPEKGYLAVAVVKKSSGPDLNWNNLKGKKSCHTAVDRTAGWNIPMG LLYNKINSCKFDQFFGEGCAPGSQRNSSLCALCIGSERAPGRECLANNHERYYGYTGAFRCLVEKGDVAF VKDQVVQQNTDGKNKDDWAKDLKQMDFELLCQNGAREPVDNAENCHLARAPNHAVVARDDKVTCVAEELL KQQAQFGRHVTDCSSSFCMFKSNTKDLLFRDDTQCLARVGKTTYESYLGADYITAVANLRKCSTSKLLEA CTFHSAKNPRVETTT Mature Porcine transferrin protein sequence (SEQ ID NO: 5) QKTVRWCTISNQEANKCSSFRENMSKAVKNGPLVSCVKKSSYLDCIKAI RDKEADAVTLDAGLVFEAGLAPYNLKPVVAEFYGQKDNPQTHYYAVAVVKKGSNFQWNQLQGKRSCHTGL GRSAGWIIPMGLLYDQLPEPRKPIEKAVASFFSSSCVPCADPVNFPKLCQQCAGKGAEKCACSNHEPYFG YAGAFNCLKEDAGDVAFVKHSTVLENLPDKADRDQYELLCRDNTRRPVDDYENCYLAQVPSHAVVARSVD GQEDSIWELLNQAQEHFGRDKSPDFQLFSSSHGKDLLFKDSANGFLRIPSKMDSSLYLGYQYVTALRNLR EEISPDSSKNECKKVRWCAIGHEETQKCDAWSINSGGKIECVSAENTEDCIAKIVKGEADAMSLDGGYIY IAGKCGLVPVLAENYKTEGENCVNTPEKGYLAVAVVKKSSGPDLNWNNLKGKKSCHTAVDRTAGWNIPMG LLYNKINSCKFDQFFGEGCAPGSQRNSSLCALCIGSERAPGRECLANNHERYYGYTGAFRCLVEKGDVAF VKDQVVQQNTDGKNKDDWAKDLKQMDFELLCQNGAREPVDNAENCHLARAPNHAVVARDDKVTCVAEELL KQQAQFGRHVTDCSSSFCMFKSNTKDLLFRDDTQCLARVGKTTYESYLGADYITAVANLRKCSTSKLLEA CTFHSAKNPRVETTT Porcine transferrin nucleotide sequence (SEQ ID NO: 6) ATGAGGCTTGCTGTGAGAGCTTTGCTTGCTTGCGCTGTGCTTGGTCTTTCTCTTGCTGTGGCTCAAAAGACTGTGCG GTGGTGCACTATCAGCAATCAAGAGGCTAACAAGTGCAGCAGCTTCCGTGAGAACATGAGCAAGGCTGTGAAGAACG GTCCTCTTGTGAGCTGCGTGAAGAAGTCATCTTACCTGGACTGCATCAAGGCCATCAGGGACAAAGAAGCTGACGCT GTTACTCTGGATGCTGGTCTTGTTTTCGAGGCTGGTTTGGCTCCTTACAACCTTAAGCCTGTTGTGGCTGAGTTCTA CGGCCAGAAGGATAATCCTCAGACTCACTACTACGCTGTGGCCGTTGTTAAGAAGGGCTCTAACTTCCAGTGGAACC AGCTGCAGGGTAAGAGATCTTGCCATACTGGTCTTGGTAGGTCCGCTGGTTGGATTATTCCTATGGGTCTGCTGTAC GATCAGCTGCCTGAACCTAGAAAGCCTATCGAGAAGGCTGTGGCCAGCTTCTTCTCTTCTTCATGTGTTCCTTGCGC TGACCCTGTGAACTTCCCTAAGCTTTGTCAACAGTGCGCTGGTAAGGGTGCTGAGAAGTGTGCTTGCTCTAATCACG AGCCTTACTTCGGTTACGCTGGCGCTTTCAACTGCCTGAAAGAAGATGCTGGCGACGTTGCATTCGTGAAGCACTCT ACTGTGCTTGAGAACCTGCCTGATAAGGCTGATAGGGATCAGTACGAGCTTCTGTGCAGGGATAACACTAGAAGGCC TGTGGATGACTACGAGAACTGCTACTTGGCTCAGGTGCCATCTCATGCTGTGGTTGCTAGATCTGTGGATGGCCAAG AGGATTCTATTTGGGAGCTTCTGAACCAGGCTCAAGAGCACTTTGGTAGGGATAAGAGCCCTGACTTCCAGCTGTTC TCTAGCTCTCACGGTAAGGACCTGCTGTTCAAGGATAGCGCTAACGGTTTCCTGCGGATCCCTAGCAAGATGGACTC TTCTCTTTACCTGGGCTACCAGTACGTTACCGCTCTTAGGAATCTGCGGGAAGAGATCAGCCCAGACTCTTCTAAGA ACGAGTGCAAGAAAGTGAGGTGGTGCGCTATTGGTCACGAAGAGACTCAAAAGTGCGACGCCTGGTCTATCAACAGC GGTGGTAAGATTGAGTGCGTGTCAGCTGAGAATACCGAGGACTGCATTGCCAAGATCGTGAAGGGTGAAGCTGATGC CATGAGCCTTGATGGTGGCTACATCTACATTGCTGGTAAGTGCGGTCTTGTGCCTGTGTTGGCTGAGAATTACAAGA CCGAGGGTGAGAACTGCGTGAACACTCCTGAGAAGGGTTACCTTGCTGTTGCCGTGGTCAAGAAGAGTAGCGGTCCT GATCTTAACTGGAACAACCTGAAGGGCAAGAAGTCTTGTCACACTGCTGTGGATAGAACCGCTGGCTGGAATATCCC AATGGGCCTCCTTTACAACAAGATCAACAGCTGCAAGTTCGACCAGTTCTTCGGTGAAGGTTGTGCTCCTGGTTCTC AGAGGAACTCTTCTTTGTGCGCTCTGTGCATTGGTTCTGAACGTGCTCCAGGTAGAGAGTGCCTTGCTAACAATCAC GAGAGGTACTACGGTTACACCGGGGCTTTTAGATGCCTGGTGGAAAAGGGTGATGTGGCCTTCGTTAAGGATCAGGT GGTGCAGCAGAACACCGATGGCAAGAACAAGGATGACTGGGCCAAAGACCTGAAGCAGATGGATTTCGAGCTGCTGT GTCAGAACGGTGCTAGGGAACCTGTTGATAACGCTGAGAACTGTCATCTGGCTAGGGCTCCTAATCACGCTGTTGTT GCAAGGGATGACAAGGTGACATGCGTGGCAGAAGAGTTGTTGAAGCAGCAGGCTCAGTTCGGTAGGCATGTGACTGA TTGCAGCTCCAGCTTCTGCATGTTCAAGAGCAACACCAAGGATCTGCTTTTCAGGGACGATACCCAGTGCTTGGCTA GAGTGGGTAAGACTACCTACGAGAGCTATCTGGGCGCTGATTACATTACCGCTGTGGCTAATCTGCGGAAGTGCTCT ACCTCTAAGCTTTTGGAGGCTTGCACCTTCCACAGCGCTAAGAATCCTAGGGTTGAGACTACCACCTAG Alternatively, the transferrin protein, inclusive of functional variants, derivatives and fragments thereof, can be derived from a fish species. Exemplary fish species include, but are not limited to, salmon, tuna, pollack, catfish, cod, haddock, sea bass, tilapia, and carp. In particular examples, the transferrin protein is derived from a teleost species, such as perch, salmon, tuna, trout, bass, swordfish etc. The nucleotide and protein sequences of teleost transferrin are publicly available (e.g., P79815 and D89084.1 of Coho salmon). An exemplary amino acid sequence is set forth in SEQ ID NO: 7 and 8. Thus, the transferrin amino acid sequence may be a protein which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO: 7 or SEQ ID NO: 8 or a fragment or derivative thereof. An exemplary encoding nucleotide sequence (i.e., mRNA transcript) is set forth in SEQ ID NO: 9. Thus, the encoding nucleotide sequence of transferrin may be a nucleic acid which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO: 9 or a fragment or derivative thereof. Full length Teleost transferrin protein sequence (SEQ ID NO: 7) MKLLLVSALLGCFATVYAAPAEGMVRWCVKSEKELKKCHDLAANVAGFSCVRRDDSLECI QAIKREEADAITLDGGDIYIAGLHNYNLQPIIAEDYGEDSDTCYYAVAVAKKGTEFGFLD LRGKKSCHTGLGKSAGWNIPIGTLVTVGQIQWAGIEDRPVESAVSDFFNASCAPGANRDS QLCQLCMGDCSRSHNEPYYDYSGAFQCLKDGAGEVAFIKHLTVPAAEKASYELLCKDNTR APIDSYKTCHLARVPAHAVVSRKDPRLANLIYSKLMAVTNFNLFSSDGYAAKNLMFKDST QNLVQLPMTTDSFLYLGAEYMSTIRSLTKAQATGVTSRAIKWCAVGHKEKVKCDAWTINS FTDGDSRIECQDAPTVDECIKKIMRKEADAIAVDGGEVFTAGKCGLVPVMVEQYDEVRCS APGEASSYFAVAVAKRGSGLTWTTLKGKRSCHTGLGRTAGWNIPMGLIHRRTMNCDFTTY FSKGCAPGFEVDSPFCAQCKGSGKSVGGDGSKCKASSEEQYYGYNGAFRCLVEDAGDVAF IKHTIVPEMTDGSGPVWAQNLMSSDFELLCQDGTTKPVTHFRECHLAKVPAHAVITRPES RGEVVSILLEQQARFGSSGSDSSFNMFKPDFGKNLLFKDSTKCLQEIPSGTKFQGFLGEE YMIAMQSLRECSNSTSDLEKACTFHSC Mature Teleost transferrin protein sequence (SEQ ID NO: 8) APAEGMVRWCVKSEKELKKCHDLAANVAGFSCVRRDDSLECI QAIKREEADAITLDGGDIYIAGLHNYNLQPIIAEDYGEDSDTCYYAVAVAKKGTEFGFLD LRGKKSCHTGLGKSAGWNIPIGTLVTVGQIQWAGIEDRPVESAVSDFFNASCAPGANRDS QLCQLCMGDCSRSHNEPYYDYSGAFQCLKDGAGEVAFIKHLTVPAAEKASYELLCKDNTR APIDSYKTCHLARVPAHAVVSRKDPRLANLIYSKLMAVTNFNLFSSDGYAAKNLMFKDST QNLVQLPMTTDSFLYLGAEYMSTIRSLTKAQATGVTSRAIKWCAVGHKEKVKCDAWTINS FTDGDSRIECQDAPTVDECIKKIMRKEADAIAVDGGEVFTAGKCGLVPVMVEQYDEVRCS APGEASSYFAVAVAKRGSGLTWTTLKGKRSCHTGLGRTAGWNIPMGLIHRRTMNCDFTTY FSKGCAPGFEVDSPFCAQCKGSGKSVGGDGSKCKASSEEQYYGYNGAFRCLVEDAGDVAF IKHTIVPEMTDGSGPVWAQNLMSSDFELLCQDGTTKPVTHFRECHLAKVPAHAVITRPES RGEVVSILLEQQARFGSSGSDSSFNMFKPDFGKNLLFKDSTKCLQEIPSGTKFQGFLGEE YMIAMQSLRECSNSTSDLEKACTFHSC Teleost transferrin nucleotide sequence (SEQ ID NO: 9) TTTCGAGAACATGAAACTGCTTCTCGTCTCAGCGCTGCTGGGGTGCTTCGCTACGGTGTATGCTGCCCCA GCTGAGGGAATGGTTAGATGGTGCGTAAAGTCGGAAAAAGAGCTGAAGAAATGCCACGATCTCGCAGCCA ATGTGGCGGGGTTTTCATGCGTGAGGAGGGACGACTCTCTTGAATGCATCCAAGCCATCAAGAGGGAAGA GGCTGATGCTATCACTCTGGATGGAGGAGATATTTACATAGCTGGCCTCCACAACTACAACCTGCAGCCC ATCATTGCAGAGGACTATGGTGAGGACTCTGACACCTGCTATTATGCTGTGGCCGTGGCCAAAAAGGGCA CTGAATTTGGGTTCCTCGACCTCCGTGGCAAGAAGTCCTGCCACACCGGGTTGGGCAAATCTGCAGGCTG GAACATTCCCATCGGTACCCTGGTGACTGTGGGCCAGATCCAATGGGCCGGCATCGAGGACAGACCTGTG GAGTCGGCGGTGAGCGACTTCTTCAATGCCAGCTGTGCTCCAGGAGCCAATAGGGATTCTCAACTGTGCC AGTTGTGTATGGGAGACTGCTCCAGATCTCACAACGAGCCCTACTATGACTATTCCGGGGCCTTCCAGTG CCTGAAGGATGGAGCAGGAGAGGTTGCCTTCATCAAGCACCTGACTGTACCTGCCGCAGAGAAGGCAAGC TATGAGTTGCTGTGCAAGGATAACACCAGAGCTCCCATCGACAGCTACAAGACCTGCCACCTGGCCAGAG TACCCGCCCACGCTGTGGTCAGCCGCAAGGACCCCAGGCTGGCCAATCTCATCTACAGCAAGCTGATGGC CGTCACGAACTTCAACCTGTTCTCCTCCGATGGTTATGCTGCCAAGAACCTGATGTTCAAGGACTCCACT CAGAATCTAGTACAGCTGCCAATGACCACCGACTCCTTCCTCTACCTGGGAGCTGAGTACATGAGCACTA TACGCTCCCTGACAAAAGCGCAGGCCACAGGTGTCACCTCCAGGGCCATCAAATGGTGTGCCGTGGGCCA TAAGGAGAAGGTCAAGTGTGACGCCTGGACAATCAACAGCTTCACAGATGGTGACTCCAGGATCGAATGC CAGGACGCACCCACAGTGGATGAATGCATCAAGAAGATCATGCGTAAAGAGGCAGATGCCATAGCGGTGG ATGGTGGGGAGGTGTTCACTGCTGGAAAATGTGGTCTGGTCCCTGTCATGGTGGAGCAGTATGATGAAGT TCGGTGCAGCGCCCCTGGTGAGGCGTCATCCTACTTTGCGGTGGCGGTGGCAAAGAGGGGATCTGGGTTG ACCTGGACAACCCTGAAGGGCAAGAGGTCATGCCACACCGGCTTGGGCAGGACCGCAGGCTGGAACATAC CCATGGGTCTTATCCATAGGAGGACTATGAACTGCGACTTCACCACATACTTCAGTAAGGGCTGTGCTCC TGGATTTGAGGTGGACTCTCCCTTCTGTGCCCAGTGTAAGGGCAGTGGGAAGTCCGTGGGAGGAGATGGG TCCAAGTGCAAAGCCAGCTCTGAAGAGCAGTACTACGGCTATAACGGAGCATTCAGATGTCTGGTTGAAG ATGCTGGAGATGTTGCCTTCATTAAACACACTATTGTACCAGAGATGACTGATGGTAGTGGTCCAGTTTG GGCACAGAACCTGATGTCCTCTGACTTTGAACTACTCTGCCAGGATGGTACTACCAAGCCAGTCACACAT TTCCGTGAGTGCCACCTGGCCAAGGTGCCCGCCCATGCTGTGATAACACGCCCAGAGTCCCGTGGAGAGG TTGTGTCCATCCTTCTGGAGCAGCAGGCCAGGTTCGGCTCAAGCGGCAGCGATTCCTCATTTAATATGTT CAAGCCAGATTTTGGAAAGAACTTGCTCTTCAAGGATTCCACAAAGTGTCTCCAGGAGATCCCAAGCGGC ACCAAATTCCAGGGTTTCCTTGGGGAAGAGTACATGATCGCCATGCAATCGCTCAGGGAGTGCTCCAACA GTACCTCAGATTTGGAGAAGGCATGCACTTTCCATTCCTGCTAGCAGAAGACATAGTGGAGCTTACCTTT GTGGCAAGCACACACTCTCTCTCCAAACCCCTCAACGTTCAAGAAACCTAAGCAGTGACTGTAGATGAAA CTGAATTCAGTTGAGAATTTTTGTACAAAACAATCTTGTATGAAAATGTGCTTTACGTTCCTTTGATAAA ACGAGTGTTAAATGAATTACGCTAAATTACTACTACTACTGTTTACTTTGTAGTTGAAATGTTAACCAAA CCATAACCAGTTCTTGAAGTATTTCTAGGAGATTACAGGTTTCTAAAATCACCTTTTTTATTCGCCGTCC TGCTCATAAATTGCAGTCTAACCAAACACTGAGGTCCAATTCACATTTGTTTTGGTTGTTCAGTGAATTG GCCAACAGCTTTGGCTTACTTTCTTGAAATAAAGTGTACCCTATTTCACAAGCT According to other examples, the transferrin protein, inclusive of functional variants, derivatives and fragments thereof, can be derived from a bird or avian species and more particularly a poultry species. The nucleotide and protein sequences of poultry transferrin (i.e., ovotransferrin) are publicly available (e.g., P02789 and NM_205304.2 of Gallus gallus (chicken)). An exemplary amino acid sequence is set forth in SEQ ID NOs: 10 and 11. Thus, the transferrin amino acid sequence may be a protein which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO: 10 or SEQ ID NO: 11 or a fragment or derivative thereof. An exemplary encoding nucleotide sequence (i.e., mRNA transcript) is set forth in SEQ ID NO: 12. Thus, the encoding nucleotide sequence of transferrin may be a nucleic acid which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO: 12 or a fragment or derivative thereof. Full length Chicken transferrin protein sequence (SEQ ID NO: 10) MKLILCTVLSLGIAAVCFAAPPKSVIRWCTISSPEEKKCNNLRDLTQQERISLTCVQKAT YLDCIKAIANNEADAISLDGGQAFEAGLAPYKLKPIAAEVYEHTEGSTTSYYAVAVVKKG TEFTVNDLQGKTSCHTGLGRSAGWNIPIGTLLHRGAIEWEGIESGSVEQAVAKFFSASCV PGATIEQKLCRQCKGDPKTKCARNAPYSGYSGAFHCLKDGKGDVAFVKHTTVNENAPDQK DEYELLCLDGSRQPVDNYKTCNWARVAAHAVVARDDNKVEDIWSFLSKAQSDFGVDTKSD FHLFGPPGKKDPVLKDLLFKDSAIMLKRVPSLMDSQLYLGFEYYSAIQSMRKDQLTPSPR ENRIQWCAVGKDEKSKCDRWSVVSNGDVECTVVDETKDCIIKIMKGEADAVALDGGLVYT AGVCGLVPVMAERYDDESQCSKTDERPASYFAVAVARKDSNVNWNNLKGKKSCHTAVGRT AGWVIPMGLIHNRTGTCNFDEYFSEGCAPGSPPNSRLCQLCQGSGGIPPEKCVASSHEKY FGYTGALRCLVEKGDVAFIQHSTVEENTGGKNKADWAKNLQMDDFELLCTDGRRANVMDY RECNLAEVPTHAVVVRPEKANKIRDLLERQEKRFGVNGSEKSKFMMFESQNKDLLFKDLT KCLFKVREGTTYKEFLGDKFYTVISSLKTCNPSDILQMCSFLEGK Mature Chicken transferrin protein sequence (SEQ ID NO: 11) APPKSVIRWCTISSPEEKKCNNLRDLTQQERISLTCVQKAT YLDCIKAIANNEADAISLDGGQAFEAGLAPYKLKPIAAEVYEHTEGSTTSYYAVAVVKKG TEFTVNDLQGKTSCHTGLGRSAGWNIPIGTLLHRGAIEWEGIESGSVEQAVAKFFSASCV PGATIEQKLCRQCKGDPKTKCARNAPYSGYSGAFHCLKDGKGDVAFVKHTTVNENAPDQK DEYELLCLDGSRQPVDNYKTCNWARVAAHAVVARDDNKVEDIWSFLSKAQSDFGVDTKSD FHLFGPPGKKDPVLKDLLFKDSAIMLKRVPSLMDSQLYLGFEYYSAIQSMRKDQLTPSPR ENRIQWCAVGKDEKSKCDRWSVVSNGDVECTVVDETKDCIIKIMKGEADAVALDGGLVYT AGVCGLVPVMAERYDDESQCSKTDERPASYFAVAVARKDSNVNWNNLKGKKSCHTAVGRT AGWVIPMGLIHNRTGTCNFDEYFSEGCAPGSPPNSRLCQLCQGSGGIPPEKCVASSHEKY FGYTGALRCLVEKGDVAFIQHSTVEENTGGKNKADWAKNLQMDDFELLCTDGRRANVMDY RECNLAEVPTHAVVVRPEKANKIRDLLERQEKRFGVNGSEKSKFMMFESQNKDLLFKDLT KCLFKVREGTTYKEFLGDKFYTVISSLKTCNPSDILQMCSFLEGK Chicken transferrin nucleotide sequence (SEQ ID NO: 12) ATCACAGACCCAGAGGGGACGGTCTGTGACCAACACCGCTGCTCCCCCTCCTCAACACCCAGCTCCCTGC CCCAGCATGAAGCTCATCCTCTGCACCGTGCTGTCCTTGGGGATAGCGGCTGTGTGTTTCGCCGCTCCCC CCAAGTCAGTCATCAGATGGTGCACCATATCCTCTCCAGAAGAGAAGAAATGCAACAACCTCAGGGACCT CACACAACAAGAGAGGATTTCATTGACCTGTGTGCAGAAAGCAACGTACCTTGACTGCATTAAAGCCATT GCGAATAATGAGGCAGATGCCATTAGCTTGGACGGCGGTCAAGTGTTTGAGGCAGGCCTTGCCCCATACA AGCTGAAGCCCATTGCTGCTGAGGTTTATGAACATACTGAAGGCTCCACAACCAGCTACTATGCTGTGGC CGTTGTGAAAAAAGGAACCGAATTCACCGTGAACGACTTGCAGGGCAAGACCTCCTGCCACACGGGGCTG GGCAGGTCTGCGGGCTGGAACATCCCCATTGGGACACTCATCCACCGGGGGGCCATTGAGTGGGAAGGCA TAGAATCGGGCTCAGTGGAACAAGCGGTGGCCAAGTTTTTCTCTGCCAGCTGCGTGCCCGGTGCCACCAT CGAGCAAAAACTGTGCCGTCAGTGCAAAGGAGACCCCAAAACCAAGTGTGCCCGCAATGCACCTTATTCT GGATATTCTGGAGCTTTCCATTGTTTGAAAGACGGAAAAGGAGACGTGGCTTTTGTGAAGCACACAACTG TTAATGAAAATGCCCCGGATCAGAAGGATGAGTACGAGCTGCTGTGCCTGGATGGCAGCCGGCAGCCTGT GGACAACTACAAGACCTGTAACTGGGCCAGAGTGGCTGCTCACGCCGTCGTGGCTCGGGATGACAGCAAG GTTGAAGATATCTGGAGCTTCCTCTCGAAAGCACAGAGCGACTTTGGCGTGGACACCAAGAGTGACTTCC ACCTCTTTGGGCCACCTGGAAAGAAGGACCCGGTCCTCAAAGACTTGCTTTTCAAAGACTCTGCCATAAT GCTGAAGCGCGTCCCCTCGCTGATGGATTCCCAGCTCTACCTGGGCTTTGAGTACTACAGTGCCATCCAG AGCATGCGGAAAGATCAGCTGACTCCCAGCCCCAGAGAAAACAGGATCCAATGGTGTGCAGTAGGCAAGG ATGAGAAGAGCAAGTGTGACCGCTGGAGTGTGGTGAGCAACGGGGACGTGGAGTGCACCGTGGTAGATGA GACAAAGGACTGCATCATTAAGATCATGAAAGGTGAAGCAGATGCTGTTGCCCTTGATGGAGGTCTGGTC TATACTGCTGGTGTCTGTGGCCTGGTGCCAGTGATGGCAGAACGATATGACGATGAAAGCCAATGCAGCA AAACAGATGAACGACCAGCATCATACTTTGCTGTGGCTGTCGCGAGGAAAGACAGCAACGTCAACTGGAA CAATCTGAAGGGCAAGAAATCGTGCCACACCGCTGTGGGGAGGACTGCTGGCTGGGTCATCCCCATGGGC TTGATTCACAACAGAACAGGGACCTGCAATTTCGATGAATACTTCAGCGAGGGCTGTGCTCCTGGGTCCC CTCCTAACTCCCGCCTCTGCCAGCTGTGCCAGGGCTCAGGGGGAATCCCACCGGAGAGGTGCGTCGCCAG CAGCCACGAGAAATACTTTGGATATACCGGAGCTTTACGGTGTCTGGTCGAGAAGGGTGATGTGGCCTTT GTTCAGCATTCCACCGTTGAGGAAAACACTGGCGGCAAAAACAAAGCTGATTGGGCCAAGAATCTGCAAA TGGATGACTTTGAGTTGCTGTGCACCGACGGGAGACGGGCAAACGTCATGGATTACAGGGAATGCAACCT GGCTGAAGTTCCTACCCACGCTGTGGTCGTGCGCCCAGAGAAAGCAAACAAAATCCGTGATCTGCTGGAG AGACAGGAGAAACGGTTTGGAGTAAATGGAAGCGAGAAAAGCAAGTTCATGATGTTTGAGTCTCAAAACA AAGATCTTCTGTTTAAAGACTTAACCAAGTGCCTGTTTAAAGTCCGAGAAGGAACAACATACAAGGAGTT CCTTGGAGATAAATTTTATACTGTGATTTCCAGCCTCAAAACCTGCAACCCATCAGATATCCTCCAGATG TGCAGCTTCCTTGAGGGCAAGTAAAGGGAGGGAAGGGCCCTTTCTGAAGGGGGAGGAAACTTCGCGCCAT GACTCCTCTCGTGCCCCCCGCACGGAACACTGATGTGCAGAGGGCCCTCTGCCATTGCTGCTTCCTCTGC CCTTCCTCGTCACTCTGAATGTGGCTTCTTTGCTACTGCCACAGCAAGAAATAAAATCTCAACATCTAAA TGGG By “protein” is meant an amino acid polymer. The amino acids may be natural or non- natural amino acids, D- or L-amino acids as are well understood in the art. The term “protein” includes and encompasses “peptide”, which is typically used to describe a protein having no more than fifty (50) amino acids (e.g., no more than 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50 amino acids and any range therein) and “polypeptide”, which is typically used to describe a protein having more than fifty (50) amino acids. Suitably, the transferrin protein produced by the methods herein is a mature transferrin protein (i.e., a transferrin protein which does not include a wildtype signal or leader sequence). Thus, the transferrin amino acid sequence may be a protein which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to any one of SEQ ID NOs: 1, 4, 7 or 10 or a fragment or derivative thereof. In some examples, however, the transferrin protein includes a wildtype signal sequence and one or more heterologous signal sequences. Accordingly, the transferrin amino acid sequence may be a protein which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to any one of SEQ ID NOs: 2, 5, 8 or 11 or a fragment or derivative thereof. Transferrin protein variants are contemplated for the present disclosure. As used herein, a protein, polypeptide or peptide “variant” shares a definable amino acid sequence relationship with a reference amino acid sequence. In particular examples, the reference amino acid sequence is that of a transferrin protein. As such, the reference amino acid sequence may be the amino acid sequence of any one of SEQ ID NOs: 1, 2, 4, 5, 7, 8, 10, 11 or 23. The “variant” protein, polypeptide or peptide may have one or a plurality of amino acids of the reference amino acid sequence deleted, inserted / added or substituted by different amino acids. It is well understood in the art that some amino acids may be substituted, inserted / added or deleted without changing the activity of the transferrin protein (i.e., conservative substitutions). Accordingly, one or more of the residues of a transferrin protein (e.g., those defined by SEQ ID NOs: 1, 2, 4, 5, 7, 8, 10 or 11) may be conservatively modified (e.g., by amino acid substitution or deletion) without altering the biological activity, function, or other desired property of the transferrin protein, such as its affinity or its specificity for Fe3+molecules and / or a transferrin receptor or a transferrin binding protein on the cell surface to be incorporated into the cell. It is further contemplated that one or more amino acid residues of a transferrin protein may be modified to, for example, improve the stability of the transferrin protein in the plant (e.g., improved resistance to degradation by plant proteases and degradation pathways) and / or improve the binding affinity of the transferrin protein for a transferrin receptor, such as a transferrin receptor of a different species. Suitably, the transferrin protein, inclusive of variants thereof, does not comprise or consist of a wild-type transferrin protein derived from a human or a primate species, as are known in the art. Typically seen as conservative substitutions are the replacements, one for another, among the aliphatic amino acids Ala, Val, Leu, and Ile; interchange of the hydroxyl residues Ser and Thr; exchange of the acidic residues Asp and Glu; substitution between the amide residues Asn and Gln; exchange of the basic residues Lys and Arg; and replacements among the aromatic residues Phe and Tyr. Guidance concerning which amino acid changes are likely to be phenotypically silent can be found in, for example, Bowie et al., Science 247:1306-1310 (1990). In some examples, a variant of the transferrin protein provided herein substantially retains the Fe3+and / or transferrin receptor binding ability of the unmodified, wild-type or reference transferrin protein (e.g., a functional variant). Thus, one or more amino acid residues within the transferrin protein of the present disclosure can be deleted or replaced with other amino acid residues, and the variant transferrin protein can be tested for retained function (e.g., the ability to specifically bind an Fe3+molecule and / or a transferrin receptor at high affinity) using functional assays described in the art. The terms “specifically binds” or “selectively binds” can be used interchangeably herein and shall be taken to mean that the binding interaction between a transferrin protein disclosed herein and a target molecule described herein (e.g., a Fe3+molecule or a transferrin receptor) is dependent on detection of the target molecule by the transferrin protein. Accordingly, the transferrin protein, inclusive of fragments, variants or derivatives thereof, suitably preferentially binds or recognizes the target molecule even when present in a mixture of other molecules. The formation of a complex with a target molecule that is relatively stable under physiologic conditions can also be a characteristic of such selective or specific binding by a transferrin protein. The terms “high affinity” and “relatively high affinity” are used interchangeably herein and generally refer to a binding affinity between a transferrin protein, inclusive of fragments, variants or derivatives thereof, and the target molecule of interest with a KDof at least about 10-6M (e.g., at least about 10-6, 10-7, 10-8, 10-9, 10-10, 10-11, 10-12, 10-13, 10-14, 10-15, 10-16, 10-17, 10-18, 10-19, 10-20, 10-21, 10-22M or any range therein), more particularly at least about 10-7M, even more particularly at least about 10-8M and still even more particularly at least about 10-9M. Again, the determination of such affinity may be conducted under standard competitive binding immunoassay procedures, such as equilibrium dialysis, surface plasmon resonance (SPR; e.g., Biacore assays), fluorescent-activated cell sorting (FACS) binding assays and the like. In particular examples, a binding affinity of the transferrin protein, inclusive of fragments, variants or derivatives thereof, for Fe3+is defined by a KDof about 10-18M to about 10-22M. Suitably, protein, polypeptide or peptide variants provided herein share at least 70% or 75%, more particularly at least 80% or 85% or even more particularly at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% sequence identity with a reference amino acid sequence, such as those set forth in SEQ ID NOs: 1, 2, 4, 5, 7, 8, 10, 11 or 23. The present disclosure also provides fragments of the transferrin proteins. As used herein, a “fragment” is a segment, domain, portion or region of a protein or peptide (such as those set forth in SEQ ID NOs: 1, 2, 4, 5, 7, 8, 10, 11 or 23) which constitutes less than 100% of the amino acid sequence of the protein or peptide. In general, fragments may comprise, consist essentially of or consist of up to 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, 500, 525, 550, 575, 600, 625, 650, 655, 660, 665, 670, 675, 676, 677, 678, 679, 680, 681, 682, 683, 684, 685, 686, 687, 688, 689, 690, 691, 692, 693, 694, 695, 696, 697, 698, 699, 700, 701, 702, 703, 704, 705, 706, 707, 708, 709, 710, 711, 712, 713, or 714 contiguous amino acids of a transferrin protein (such as of SEQ ID NOs: 1, 2, 4, 5, 7, 8, 10, 11 or 23). In a particular example, the protein fragment is or comprises a conserved region or one or more conserved amino acids of a transferrin protein. In various examples, the fragment comprises, or is contained within, a transferrin protein, such as those set forth in SEQ ID NOs: 1, 2, 4, 5, 7, 8, 10, 11 or 23. The present disclosure also contemplates derivatives of the transferrin proteins described herein. As used herein, “derivatives” are molecules such as proteins, fragments or variants thereof that have been altered, for example, by conjugation or complexing with other chemical moieties, by post-translational modification (e.g., phosphorylation, acetylation and the like), modification of glycosylation (e.g., adding, removing or altering glycosylation), lipidation and / or inclusion of additional amino acid sequences as would be understood in the art. Additional amino acid sequences may include fusion partner amino acid sequences which create a fusion protein. By way of example, fusion partner amino acid sequences may assist in detection and / or purification of the isolated fusion protein. Non-limiting examples include metal- binding (e.g., polyhistidine) fusion partners, maltose binding protein (MBP), Protein A, glutathione S-transferase (GST), fluorescent protein sequences (e.g., GFP), polylysine, epitope tags, such as myc, FLAG and haemagglutinin tags or an affinity tag (e.g., a streptavidin tag). Such derivatives, variants and fragments for use according to the present disclosure are suitably functional derivatives, variants and fragments of the transferrin protein. By “functional transferrin protein” is meant a transferrin protein able to reversibly bind to iron (e.g., one or two Fe3+ions) and / or a transferrin receptor with a high affinity, and more particularly the same or similar affinity as an unmodified or wild-type transferrin protein. Determining whether a transferrin protein derivative, variant or analogue is functional may be assessed by any method or means known in the art. Plants expressing the component protein It is contemplated that any species or variety of plant may be utilised for the methods of the present disclosure. Accordingly, in one form, the present disclosure provides a plant that has been configured to express a component protein, wherein the component protein is of non-human origin. As generally used herein, the term “plant” includes reference to whole plants, plant organs, plant tissues, and plant cells and progeny of same, but is not limited to angiosperms and gymnosperms, such as safflower, soybean, canola, benth / benthi, camelina, Arabidopsis, potato, tomato, tobacco (e.g., of the genus Nicotiana), alfalfa, lettuce, carrot, strawberry, beetroot, cassava, sweet potato, lima bean, pea, chick pea, maize (corn), turf grass, wheat, rice, barley, sorghum, oat, oak, eucalyptus, walnut, palm and duckweed, as well as fern and moss. Thus, a plant may be a monocot, a dicot, a vascular plant reproduced from spores such as fern or a nonvascular plant such as moss, liverwort, hornwort and algae. The word “plant,” as used herein, also encompasses plant cells, seeds, plant progeny, propagule whether generated sexually or asexually, and descendants of any of these, such as cuttings or seed. Plant cells include suspension cultures, callus, embryos, meristematic regions, callus tissue, leaves, roots, shoots, gametophytes, sporophytes, pollen, seeds and microspores. Plants may be at various stages of maturity and may be grown in liquid or solid culture. Additionally, plants of the present disclosure may be grown in soil or other suitable media in pots, greenhouses or fields. The plant may be, for example, a monocot or a dicot, such as those disclosed herein. According to particular examples, the plant is a dicot species selected from soybean, safflower, canola, camelina (Camelina sativa), benth / benthi (Nicotiana benthamiana), lima bean, Arabidopsis, tobacco, rice, maize, barley, sorghum, wheat and / or oat. More particularly, the plant is suitably a soybean plant, a safflower plant, a camelina plant, a benth plant or a canola plant. In some examples, the plant is not a rice plant. In certain examples, the plant is a soybean plant. As used herein, the term “soybean plant” refers to a legume plant of the family Fabaceae, herein used in its broadest sense and includes but is not limited to any species, variety or cultivar of soybean, for example, a Glycine species. A soybean plant may be of a Glycine max species, such as a cultivated soybean plant, a Glycine soja species, such as a wild form of soybean, and a Glycine gracilis Skvortz species, such as a weedy or semi-wild form of soybean. For other examples, the plant is a safflower plant. As used herein, the term “safflower” refers to members of the species Carthamus tinctorius, inclusive of any variety or cultivar thereof. Safflower is a highly branched, herbaceous, thistle-like plant belonging to the Asteraceae family that is commercially cultivated for vegetable oil extracted from the seeds. According to some examples, the plant is a canola plant. Brassica napus is commonly known as rapeseed or oilseed rape and specific cultivars or varieties may be referred to as canola. As used herein, the term “canola” or “canola plant” refers to a Brassica plant capable of being used to produce canola oil (i.e., an oil meeting a specific quality designation of containing less than 2% erucic acid) and includes varieties of B. napus, B. napobrassica, B. rapa, B. juncea, and B. campestris. In certain examples, the plant is a camelina plant. Camelina is a dicotyledonous plant of the Brassaceaceae family, also known as wild flax, flaxseed, German sesame, Siberian oilseed, and is native to Europe and Central Asia. It is mainly grown as a seed crop in Europe and North America. According to further examples, the plant is of the genus Nicotiana (i.e., a tobacco plant), such as N. alata, N. arentsii, N. excelsior, N. forgetiana, N. glauca, N. glutinosa, N. gossei, N. kawakamii, N. knightiana, N. langsdorffi, N. otophora, N. setchellii, N. sylvestris, N. tomentosa, N. tomentosiformis, N. undulata, N. x sanderae, N. africana, N. amplexicaulis, N. benavidesii, N. bonariensis, N. debneyi, N. longiflora, N. maritina, N. megalosiphon, N. occidentalis, N. paniculata, N. plumbaginifolia, N. raimondii, N. rosulata, N. rustica, N. simulans, N. stocktonii, N. suaveolens, N. tabacum, N. umbratica, N. velutina, and N. wigandioides, N. acaulis, N. acuminata, N. attenuata, N. benthamiana, N. cavicola, N. clevelandii, N. cordifolia, N. corymbosa, N. fragrans, N. goodspeedii, N. linearis, N. miersii, N. nudicaulis, N. obtusifolia, N. occidentalis subsp. Hersperis, N. pauciflora, N. petunioides, N. quadrivalvis, N. repanda, N. rotundifolia, N. solanifolia, and N. spegazzinii. Suitably, the plant is a benth plant or a benthi plant (i.e., is of the species Nicotiana benthamiana). Nicotiana benthamiana is a species of tobacco plant indigenous to Australia. Nucleic acid constructs are provided herein that allow for modifying or genetically engineering a plant. While the methods are exemplified herein using a dicot species (e.g., a soybean plant, a safflower plant, a camelina plant, a benth plant or a canola plant), it is envisaged that other plant species can be used in a similar manner to recombinantly express the component protein provided herein. The component proteins, crude extracts, low purity extracts, nucleic acids, genetic constructs, plants, plant parts and plant cells described herein may be considered to be isolated. For the purposes of the present disclosure, by “isolated” is meant material that has been removed from its natural state or otherwise been subjected to human manipulation. Isolated material may be substantially or essentially free from components that normally accompany it in its natural state, or may be manipulated so as to be in an artificial state together with components that normally accompany it in its natural state. Isolated material may be in native, chemical synthetic or recombinant form. Recombinant expression of component proteins Methods for producing recombinant proteins or polypeptides are well known in the art. The plant according to the present disclosure can be modified, and more particularly genetically modified, to comprise a nucleotide sequence or nucleic acid molecule encoding a component protein, such as a transferrin protein, of non-human origin. In this regard, the plant of the present disclosure may be considered transformed, transfected (inclusive of transiently transfected and stably transfected), or transgenic. The term “transgenic plant” refers to a plant in which has been introduced one or more exogenous or heterologous nucleic acids, that is, nucleic acid sequences which are not present in the native (“untransformed”) plant. The heterologous nucleic acids can be either stably integrated into the genome of the plant in question, or can be extra-chromosomally expressed (e.g., transiently expressed) from, for example, a replication-competent genetic construct or plasmid. “Transformation” refers to a process by which a nucleic acid is stably integrated into the genome of a plant or plant cell. “Stably integrated” refers to the permanent, or non-transient retention and / or expression of a nucleic acid in and by a cell genome. Thus, a stably integrated nucleic acid, such as one which encodes a component protein, is one that is a fixture within a transformed cell genome and can be replicated and propagated through successive progeny of the cell or resultant transformed or transgenic plant. The term “transgenic” is also used herein to include any cell, cell line, callus, tissue, plant part or plant, the genotype of which has been altered by the presence of heterologous nucleic acids including those transgenic plants or plant cells initially altered as well as those created by sexual crosses or asexual reproduction of the initial transgenic plants or plant cells. Accordingly, a transgenic or transformed plant or plant cell also includes progeny of the plant or plant cell and progeny produced from a breeding program employing such a transgenic plant as a parent in a cross and exhibiting an altered phenotype resulting from the presence of the coding sequence for a component protein. Hence, a plant of the present disclosure will include any plant which has a cell containing introduced nucleic acid sequences, such as those that encode a component protein, regardless of whether the sequence was introduced into the plant directly through transformation means or introduced by generational transfer from a progenitor plant or plant cell which originally received the construct by direct transformation. Transformation of plants, plant cells, plant tissues or the like may occur under natural or artificial conditions using various methods well known in the art, such as those generally described in Slater et al., Plant Biotechnology - The Genetic Manipulation of Plants, Oxford University Press (2003), and Christou and Klee, Handbook of Plant Biotechnology, John Wiley and Sons (2004). Transformation may rely on any known method for the insertion of nucleic acid sequences into a plant cell, including Agrobacterium-mediated transformation protocols, pollen-mediated transformation, viral infection, whiskers, electroporation, heat shock, lipofection, polyethylene glycol treatment, micro-injection, and particle bombardment. Agrobacterium-mediated transfer is a widely applicable system for introducing genes into plant cells because DNA can be introduced into cells in whole plant tissues, plant organs, or explants in tissue culture, for either transient expression, or for stable integration of the DNA in the plant cell genome. The use of Agrobacterium-mediated plant integrating vectors to introduce DNA into plant cells is well known in the art (see, for example, US 5,177,010, US 5,104,310, US 5,004,863, or US 5,159,135). Another example of a suitable method for delivering transforming nucleic acid molecules to plant cells is microprojectile or particle bombardment. This method has been reviewed by Yang et al., Particle Bombardment Technology for Gene Transfer, Oxford Press, Oxford, England (1994). Generally, non-biological particles (microprojectiles) are coated with nucleic acids and delivered into cells by a propelling force. In another example, plastids can be stably transformed. Methods disclosed for plastid transformation in higher plants include particle gun delivery of DNA containing a selectable marker and targeting of the DNA to the plastid genome through homologous recombination (see, e.g., US 5,451,513, US 5,545,818, US 5,877,402, US 5,932479, and WO 99 / 05265). Transformation of plant protoplasts can be achieved using methods based on calcium phosphate precipitation, polyethylene glycol treatment, electroporation, and combinations of these treatments. Application of these systems to different plant varieties depends upon the ability to regenerate that particular plant strain from protoplasts. Illustrative methods for the regeneration of cereals from protoplasts are described (see, e.g., Fujimura et al., 1985; Toriyama et al., 1986; Abdullah et al., 1986). Other methods of cell transformation can also be used and include but are not limited to the introduction of DNA into plants by direct DNA transfer into pollen, by direct injection of DNA into reproductive organs of a plant, or by direct injection of DNA into the cells of immature embryos followed by the rehydration of desiccated embryos. For the transformation of safflower plants, particularly useful methods are described by Belide et al. (2011, Plant Methods, 7:12). Similarly, exemplary methods for the transformation of canola plants and soybean plants are provided in Cardoza & Stewart (2003, Plant Cell Rep, 21(6):599-604) and Yang et al. (2019, Plant Signaling & Behavior, 14:7) respectively. Methods for the transformation of benth plants and camelina plants are disclosed in Cody et al. (2023, Nature Protocols 18, pages 81–107) and Sitther et al. (2018, J Biol Methods. 5(1): e83) respectively. The regeneration, development, and cultivation of plants from single plant protoplast transformants or from various transformed explants is well known in the art (see, e.g., Weissbach et al., In: Methods for Plant Molecular Biology, Academic Press, San Diego, Calif., (1988)). This regeneration and growth process typically includes the steps of selection of transformed cells, culturing those individualized cells through the usual stages of embryonic development through the rooted plantlet stage. Transgenic embryos and seeds are similarly regenerated. The resulting transgenic rooted shoots are thereafter planted in an appropriate plant growth medium, such as soil or vermiculite. The development or regeneration of plants containing the foreign, exogenous gene is well known in the art. Suitably, the regenerated plants are self-pollinated to provide homozygous transgenic plants. Otherwise, pollen obtained from the regenerated plants is crossed to seed-grown plants of agronomically important lines. Conversely, pollen from plants of these important lines is used to pollinate regenerated plants. A transgenic plant of the present invention containing a desired polynucleotide is cultivated using methods well known to one skilled in the art. To confirm the presence of the transgenes in transgenic cells and plants, a polymerase chain reaction (PCR) amplification or Southern blot analysis can be performed using methods known to those skilled in the art. Once transgenic plants have been obtained, they may be grown to produce plant tissues or parts having the desired phenotype. The plant tissue or plant parts, may be harvested, and / or the seed collected. The seed may serve as a source for growing additional plants with tissues or parts having the desired characteristics (e.g., express a transferrin protein of non- human origin). Following transformation, the nucleic acid encoding the component protein is suitably stably expressed by the plant (e.g., stable nuclear expression or stable chloroplast expression of the component protein). As used herein, the terms “stably expressed” or “stable expression” refer to expression and accumulation of a protein, such as a transferrin protein, in a plant cell over time. In some examples, a protein may accumulate because it is not degraded by endogenous plant proteases. For certain examples, a protein is considered to be stably expressed in a plant if it is present in the plant in an amount of 1% or higher (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20% or higher) per total protein content of protein, and more particularly soluble protein, extractable from the plant. In other words, the plant may be considered to be stably transformed with the nucleic acid encoding the component protein. As used herein, the terms “stably transforming”, “stably transformed” and variations thereof refer to the integration of the polynucleotide into the genome of the cell such that they are transferred to progeny cells during cell division without the need for positively selecting for their presence. Gene-targeting tools, such as ZFNs, TALENs and CRISPR systems, as are well known in the art, may be utilised to target stable integration of an expression cassette to a particular locus of the genome of the plant in question. Stable transformants, or progeny thereof, can be selected and / or identified by any means known in the art such as Southern blots on chromosomal DNA, or in situ hybridization of genomic DNA. According to other examples, the plant may be configured to transiently express, rather than stably express, the component protein. The term “transient expression” or “transiently expressed” in the context of expression of a gene or nucleotide sequence refers to the expression of a gene or nucleotide sequence that is not integrated into the host chromosome, but which can function either independently (e.g., by being a part of an autonomously replicating plasmid or an expression cassette) or as a part of another biological system, such as a virus, for example. Transient expression may be achieved by “transient transformation” of a host cell, which refers to the introduction of foreign DNA or a nucleotide sequence of interest into the host cell (for example, by such methods as Agrobacterium-mediated transformation or biolistic bombardment) without integration of the foreign DNA or nucleotide sequence of interest into a host cell chromosome, thereby precluding stable maintenance of the foreign DNA or nucleotide sequence of interest in the progeny of the host cell. Methods of transiently expressing proteins in plants are well known in the art and may include polyethylene glycol (PEG)-mediated or electroporation-mediated transformation of protoplasts, plant viruses, such as the tobacco mosaic virus (TMV), infiltration of Agrobacterium tumefaciens (agroinfiltration), and biolistic bombardment (see, e.g., Davis et al., 2020, Front Plant Sci; and reviewed in Nosaki et al.2021, Plant Biotechnol (Tokyo), Sep 25; 38(3): 297–304). For the present disclosure, it is envisaged that the nucleotide sequence encoding the component protein described herein may be part of a genetic construct (e.g., a vector, such as an expression vector or cassette). An exemplary genetic construct for the expression of a transferrin protein is provided in SEQ ID NOs: 13 and 22. The nucleotide sequence encoding the component protein can be part of a genetic construct that is transiently or stably expressed by using respective means and methods which are well known to the person skilled in the art, such as those described above. In one form, the present disclosure provides an isolated nucleic acid comprising, consisting of or consisting essentially of the nucleotide sequence set forth in SEQ ID NOs: 14 or a fragment, variant or derivative thereof. In another form, the present disclosure provides an isolated genetic construct or vector comprising, consisting of or consisting essentially of the nucleotide sequence set forth in SEQ ID NO: 13 or 22 or a fragment, variant or derivative thereof. For the purposes of host cell expression, the genetic construct is suitably an expression construct. For some examples, the expression construct comprises the nucleotide sequence encoding the component protein operably linked to one or more additional sequences in an expression vector. The terms “polynucleotide” and “nucleic acid” are used interchangeably herein. They refer to a polymeric form of nucleotides of any length, either deoxyribonucleotides or ribonucleotides. A polynucleotide defined herein may be of genomic, cDNA, semisynthetic, or synthetic origin, double-stranded or single-stranded and by virtue of its origin or manipulation: (1) is not associated with all or a portion of a polynucleotide with which it is associated in nature, (2) is linked to a polynucleotide other than that to which it is linked in nature, or (3) does not occur in nature. Preferred polynucleotides of the invention encode a component protein which are capable of being transcriptionally and translationally expressed in plant cells. Also contemplated are variants of the nucleic acids described herein. Variants may comprise a nucleotide sequence at least 70%, at least 75%, preferably at least 80%, at least 85%, more preferably at least 90%, 91%, 93%, 94%, 95%, 96%, 97%, 98% or 99% nucleotide sequence identity with any nucleotide sequence encoding the component protein or regulatory sequences of the present disclosure (e.g., SEQ ID NOs: 3, 6, 9, 12-17, 22). The present disclosure also provides nucleic acids that have been modified such as by taking advantage of codon sequence redundancy. In a more particular example, codon usage may be modified to optimize expression of a nucleic acid in a particular organism or cell type. In some examples, the nucleic acids provided herein (e.g., SEQ ID NOs: 3, 6, 9 and 12) are codon optimized for expression in a plant. The nucleic acids, expression cassettes, genetic constructs, vectors and the like disclosed herein can be conveniently prepared using standard protocols such as those described in Chapter 2 and Chapter 3 of CURRENT PROTOCOLS IN MOLECULAR BIOLOGY (Eds. Ausubel et al. John Wiley & Sons NY, 1995-2008). As used herein, the terms “vector” and “expression vector” are understood to mean any nucleic acid molecule including a nucleotide sequence competent to be incorporated into a host cell and integrated into the host cell genome, or to replicate autonomously as an episomal DNA. Such vectors include linear nucleic acids, plasmids, phagemids, cosmids, RNA vectors, viral vectors and the like. Suitable expression vectors may comprise regulatory nucleotide sequences, such as promoter sequences, leader or signal sequences, ribosomal binding sites, polyadenylation sequences, transcriptional start and termination sequences, and enhancer or activator sequences. The expression vector may also include an additional nucleotide sequence encoding a selection marker or selection cassette, such as ampR, neoR, zeoRor kanR, although without limitation thereto. Accordingly, the genetic construct described herein may further include one or more regions preceding and following the coding region, such as a 5’ untranslated region (5’ UTR) or “leader” sequence and / or a 3’ UTR or “trailer” sequences, as well as intervening sequences (introns) between individual coding segments (exons) of the component protein. The 5′ UTRs and 3′ UTRs may be selected from those that have been identified to result in enhanced recombinant protein expression in plants (see, e.g., PCT / US2019 / 020621, the contents of which are incorporated by reference herein). Such 5’ and / or 3’ UTR sequences are suitably derived from a plant (e.g., Nicotiana benthamiana NbPsaK, N. benthamiana actin (NbACT3), potato proteinase inhibitor II (Pin2), A. thaliana heat shock protein (AtHSP), pea rubisco small subunit 3′ UTR (RbcS)), a bacterium (e.g., Agrobacterium nopaline synthase (NOS)) or a plant virus (e.g., tobacco mosaic virus (TMV), barley yellow mosaic virus, cowpea mosaic virus, bean dwarf mosaic virus, cauliflower mosaic virus (CaMV), and pea enation mosaic virus). The sequences of such 5’ and 3’ UTRs are well-known in the art. In particular examples, the genetic construct described herein includes a 5’ UTR and / or a 3’ UTR at least partly derived from a TMV and / or a CaMV. Thus, the 5’ UTR nucleotide sequence may be or comprise a nucleic acid which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO: 15 or a fragment or derivative thereof. By “operably linked” is meant that said additional nucleotide sequence(s) is / are positioned relative to the nucleic acid of the present disclosure suitably to initiate, regulate or otherwise control transcription. Suitably, the nucleotide sequence encoding the component protein is operably linked to a promoter, such as an inducible or conditional promoter or a constitutive promoter. The use of any kind of promoter is envisaged, provided that the promoter is able to control the transcription of the nucleotide sequence encoding the component protein operably linked thereto in a plant. However, in particular examples, the promoter is derived from a plant virus, such as a constitutive plant virus promoter. According to particular examples, the promoter is an inducible promoter, inclusive of modified and unmodified versions thereof. To this end, an inducible promoter can be used to advantageously control the expression rate of the nucleotide sequence encoding the component protein within the plant. It may therefore be possible to control or modulate the expression rate of the component protein in various stages of cultivation of the plant and consequently to determine the point in time when: (a) to start and / or stop expression of the component protein in the plant; and / or (b) the level of the component protein within the plant reaches a predetermined or threshold amount or concentration. Such inducible promoters may be induced under certain stress conditions, such as abiotic stress and biotic stress. Generally, stress-inducible promoters contain a cis-acting sequence which is recognised by specific transcription factors that induce the synthesis of proteins only under conditions of stress. Exemplary stress-inducible promoters include the HSP18.2 promoter from Arabidopsis thaliana (responsive to thermal shock), the Rd29 promoter from Arabidopsis thaliana (responsive to osmotic stress), the adh promoter from Arabidopsis thaliana (responsive to dehydration and cold stress), the ThGLP promoter from Tamarix hispida (responsive to drought, salt and low temperature) and the rbcS-3A promoter from Pisum sativum (responsive to light). Alternatively, the present disclosure further contemplates the use of promoters which act constitutively in the plant. Constitutive promoters for the recombinant expression of proteins within transgenic plants are well known in the art. Moreover, it is contemplated that a combination of inducible and constitutive promoters can be combined to further increase the expression of any of the nucleotide sequences operably linked thereto. The most common promoters used for constitutive overexpression in plants are derived from plant virus sources, such as the cauliflower mosaic (CaMV) 35S promoter (Odell et al. (1985) Nature, 313: 810-812). Other viral promoters are also well known to those of skill in the art. These include, but are not limited to, the CaMV 19S promoter, the cassava vein mosaic virus (CsVMV) promoter, the Australian banana streak virus (BSV) promoters, the Mirabilis mosaic virus (MMV) promoter, the Strawberry Vein Banding virus (SVBV) promoter and the figwort mosaic virus (FMV) promoter. Endogenous plant promoters can also be used to drive transgene expression in plants. These constitutive promoters may be derived, for example, from actin and ubiquitin genes (e.g., the Act2 promoter from Arabidopsis, the rice actin 1 gene (Act1) promoter for use in cereal systems and the maize ubiquitin 1 promoter (pUbi)). A number of tissue-specific promotor or expression systems (e.g., specific to fruit, seed / grain, tubers / root storage systems, florets / flowers, leaves / green tissue, anthers / pollen, and the like) are also known. To this end, and in particular examples, the promoter is a green tissue- or leaf-specific promoter. Promoters specific to leaves / green tissues include, but are not limited to, promoters from the rbcS multigene family encoding the small subunit of ribulose-1,5-bisphosphate carboxylase (e.g., the pea rbcS-3A promoter and the alfalfa rbcS promoter), promoters from the chlorophyll a / b-binding (Cab) protein genes (e.g., the CAB2 promoter from Arabidopsis) and the alfalfa RAc promoter. According to alternative examples, the promoter utilised for the present disclosure is a seed-specific promoter or an endosperm-specific promoter. Illustrative seed-specific promoters include, but are not limited to, the promoters of various seed storage proteins, such as the endosperm-specific hordein promoters in barley, glutenin promoters from wheat, the zein promoters in maize, and the granule-bound starch synthase 1 (gbss1) gene in wheat. Other seed- specific promoters include, for example, those from the soybean β-conglycinin, the sunflower helianthinin genes, the French bean β-phaseolin gene, and the cotton-globulin promoter. In some instances, the promoter can be native to the same plant species as the plant into which the genetic construct of the present disclosure has been introduced. In other examples, the promoter is derived from a plant species heterologous to the plant in question. In certain examples, the promoter is or comprises a CaMV promoter, or a fragment, variant or derivative thereof. More particularly, the promoter suitably is or comprises a CaMV 35S promoter, or a fragment, variant or derivative thereof. According to certain examples, the nucleotide sequence encoding the component protein is operably linked to two CaMV 35S promoters. A non-limiting example of a CaMV 35S promoter is provided in or contained within the 5’ UTR of SEQ ID NO: 15 below. The nucleic acid molecule described herein may also comprise a nucleic acid sequence which encodes a signal sequence. A “signal sequence” is an N- or C-terminal polypeptide sequence which is effective to localize the peptide or protein (e.g., the component protein) to which it is attached to a selected intracellular or extracellular region, such as an intracellular vacuole or other protein storage body, chloroplast, mitochondria, endoplasmic reticulum, or extracellular space. The signal sequence used in the present invention may be an amino acid sequence initiating transport of a protein, and more particularly, a component protein, across the membrane of the endoplasmic reticulum (ER). In some examples, the signal sequence targets the attached peptide or protein to an endosperm cell, or more particularly, an organelle in a seed specific cell type, such as an endosperm-cell organelle (e.g., mitochondria, cytosol, chloroplast). Exemplary signal sequences include those sequences associated with the maturation- specific genes. For example, the signal sequence can be a glutelin signal sequence, a prolamine signal sequence, a hordein signal sequence, a gliadin signal sequence, a glutenin signal sequence, a zein signal sequence, an albumin signal sequence, a globulin signal sequence, an ADP glucose pyrophosphorylase signal sequence, a starch synthase signal sequence, a branching enzyme signal sequence and an LEA signal sequence. The signal sequence may also include a native or wildtype signal sequence of the component protein. It is further contemplated that the genetic construct may comprise a nucleotide sequence encoding more than one signal sequence (e.g., a plurality – 2, 3, 4, 5, 6 etc. – of signal sequences). In particular examples, the signal sequence is or comprises a glutelin 1 (GT1) signal sequence, or more particularly, a rice-derived GT1 signal sequence. An exemplary nucleotide sequence encoding a GT1 signal sequence is provided in SEQ ID NO: 16 below, but functional fragments, variants and derivatives thereof are envisaged. Thus, the GT1 signal sequence may be encoded by a nucleic acid which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO: 16 or a fragment or derivative thereof. The nucleotide sequence encoding the component protein may also be operably linked to a terminator sequence which blocks or prevents transcription by a polymerase. The term “terminator sequence” refers to DNA sequences located downstream or 3’ of a coding sequence, including polyadenylation recognition sequences and other sequences encoding regulatory signals, capable of affecting mRNA processing or gene expression. Typically, a promoter will be associated to a corresponding or operably linked terminator sequence. In particular examples, the terminator is or comprises a viral terminator. According to some examples, the terminator is or comprises a CaMV terminator, or a fragment, variant or derivative thereof. More particularly, the terminator is or comprises a CaMV 35S terminator, or a fragment, variant or derivative thereof. A non-limiting example of a 3’ UTR / terminator sequence, which includes a CaMV terminator, is provided in SEQ ID NO: 17 below. Thus, the terminator sequence may be a nucleic acid which is at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical to SEQ ID NO: 17 or a fragment or derivative thereof. Terms used generally herein to describe sequence relationships between respective proteins and nucleic acids include "comparison window", "sequence identity", "percentage of sequence identity" and "substantial identity". Because respective nucleic acids / proteins may each comprise (1) only one or more portions of a complete nucleic acid / protein sequence that are shared by the nucleic acids / proteins, and (2) one or more portions which are divergent between the nucleic acids / proteins, sequence comparisons are typically performed by comparing sequences over a "comparison window" to identify and compare local regions of sequence similarity. A "comparison window" refers to a conceptual segment of, for example, 6, 9, 12 or 20 contiguous residues that is compared to a reference sequence. The comparison window may comprise additions or deletions (i.e., gaps) of about 20% or less as compared to the reference sequence for optimal alignment of the respective sequences. Optimal alignment of sequences for aligning a comparison window may be conducted by computerised implementations of algorithms (Geneworks program by Intelligenetics; GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package Release 7.0, Genetics Computer Group, 575 Science Drive Madison, WI, USA, incorporated herein by reference) or by inspection and the best alignment (i.e. resulting in the highest percentage homology over the comparison window) generated by any of the various methods selected. Reference also may be made to the BLAST family of programs as for example disclosed by Altschul et al., 1991, Nucl. Acids Res. 25 3389, which is incorporated herein by reference. A detailed discussion of sequence analysis can be found in Unit 19.3 of CURRENT PROTOCOLS IN MOLECULAR BIOLOGY Eds. Ausubel et al. (John Wiley & Sons Inc NY, 1995-1999). The term “sequence identity” is used herein in its broadest sense to include the number of exact nucleotide or amino acid matches having regard to an appropriate alignment using a standard algorithm, having regard to the extent that sequences are identical over a window of comparison. Thus, a "percentage of sequence identity" is calculated by comparing two optimally aligned sequences over the window of comparison, determining the number of positions at which the identical nucleic acid base (e.g., A, T, C, G, U) or amino acid residue occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the window of comparison (i.e., the window size), and multiplying the result by 100 to yield the percentage of sequence identity. For example, "sequence identity" may be understood to mean the "match percentage" calculated by the DNASIS computer program (Version 2.5 for windows; available from Hitachi Software engineering Co., Ltd., South San Francisco, California, USA). Genetic constructs of the present disclosure may comprise companion sequences upstream and downstream to the expression cassette comprising the nucleotide sequence encoding the component protein. The companion sequences may be of plasmid or viral origin and provide necessary characteristics to the genetic construct to permit, for example, amplification thereof in a secondary host to the plant host, such as, sequences containing an origin of replication and a selectable marker. Typical secondary hosts include bacteria and yeast. The expression construct may also include an additional nucleotide sequence encoding a fusion partner (typically provided by the expression vector) so that the recombinant protein is expressed as a fusion protein. In this regard, the component protein, such as a transferrin protein, may be expressed as a fusion protein with one or more further growth factors or cell culture components, such as those described herein (e.g., albumin), for use in a serum-free media or animal-derived component-free media, such as a serum-free media or animal-derived component- free media for use in in vitro meat production (e.g., cellular agriculture or cellular aquaculture). Such fusion proteins may configured to be cleavable, such as by way of enzymatic digestion, into their individual protein sequences. Culturing non-human animal cells It is contemplated that the non-human component protein (e.g., transferrin protein) described herein is suitable for use in culturing non-human animal cells in the process of in vitro meat production. Accordingly, in one form, the present disclosure provides a composition for producing a culture medium for culturing non-human animal cells, said composition comprising a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to the non-human animal cells and optionally one or more carriers, diluents or excipients acceptable for use in cell culture, as are known in the art. Suitably, the component protein is a transferrin protein. In a related form, the present disclosure relates to a kit for producing a culture medium for culturing non-human animal cells, said kit comprising a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to the non-human animal cells. Suitably, the component protein is a transferrin protein. To this end, it is envisaged that the component protein described herein can be formulated as discrete doses, such as in the form of a kit. Such a kit may further comprise a package insert comprising printed instructions for producing a culture medium for culturing non-human animal cells. Accordingly, the aforementioned kits are suitable for use in methods of culturing non-human animal cells and / or in vitro meat production, as described herein. The kit may further include a base medium. The terms “base medium” and “basal medium” generally refer to a solution of, for example, amino acids, vitamins, salts, and nutrients that is effective to support the growth of cells in culture, although normally these compounds will not support cell growth unless supplemented with additional compounds or components. Non-limiting examples of base media include Leibovitz's L-15 medium, Eagle's Minimum Essential Media (MEM), Medium 199, Dulbecco's Modified Eagle Medium (DMEM), Ham's F12 Nutrient Mix, Ham's F10 Nutrient Mix, MacCoy's 5A Medium, Glasgow Modified Eagle Medium (GMEM), Iscove's Modified Dulbecco's Medium, and RPMI 1640. In another form, the present disclosure provides a culture medium for culturing non-human animal cells comprising: (a) a base medium; and (b) a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to the non-human animal cells. Suitably, the component protein is a transferrin protein. According to certain examples, the culture medium or the kit includes one or more further additives. By way of example, the culture medium or the kit may include one or more growth factors or cytokines. These one or more further additives may include one or more of activin, insulin growth factor 1 (IGF-1), insulin, an interleukin (e.g., IL-6, IL-11), interleukin 6 receptor (IL-6R), fibroblast growth factor (FGF; e.g., FGF-1 and FGF-2), epidermal growth factor (EGF), platelet derived growth factor (PDGF), connective tissue growth factor (CTGF), transforming growth factor-beta (TGF-beta), a bone morphogenetic protein (BMP), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), WNT and / or albumin, inclusive of homologs, paralogs, orthologs, variants, precursors, isoforms, and combinations thereof. Suitably, the one or more growth factors or cytokines are recombinant growth factors or cytokines of the same or similar species to that of the non-human cells. In some examples, the growth factor is a chicken growth factor, a duck growth factor, a bovine growth factor, a sheep growth factor, a fish growth factor, a porcine growth factor, a mammalian growth factor, an avian growth factor or a teleost growth factor. Bacterial, yeast, insect, mammalian, or any other appropriate protein expression systems may be used to produce such recombinant growth factors or cytokines. In a further related form, the present disclosure provides a method of producing a culture medium for culturing non-human animal cells, said method including the steps of: (a) providing a base medium; (b) adding a low purity extract of a component protein to the base medium, wherein the component protein has been produced by a plant and is of a same or similar species to the non- human animal cells. Suitably, the component protein is a transferrin protein. The step of adding one or more further additives, such as those described herein, to the base medium is further contemplated for the present method. In one particular form, the present disclosure also relates to a method of culturing non- human animal cells, said method including the step of culturing the non-human animal cells in a culture medium comprising a base medium and a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to that of the non-human animal cells. Suitably, the component protein is a transferrin protein. In another broad form, the present disclosure provides a method of in vitro meat production, said method including the steps of: (a) providing a plurality of non-human animal cells; and (b) culturing the non-human animal cells in a culture medium comprising a base medium and a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to that of the non-human animal cells. Suitably, the component protein is a transferrin protein. In still another related form, the present disclosure provides a meat product produced by the aforementioned methods. Cells for the production of in vitro meat may be cells (e.g., muscle cells, somatic cells, stem cells, lipid cells etc.) taken from an animal source, which may then be grown separately from the animal in a culture media in a bioreactor or other suitable type of sterile environment. Accordingly, the present method may further include the earlier step of isolating the plurality of non-human cells from an animal source, such as an animal biopsy. In some examples, the non-human animal cells are from poultry, seafood (e.g., teleost), game or livestock (e.g., bovine, porcine, ovine, caprine), such as one of those species described herein for the source of the component protein. The cells may grow into a semi-solid or solid form mimicking an animal organ by attaching to an edible or food-grade three-dimensional scaffold that is placed in the bioreactor. Alternatively, the cells can be grown at least partly in a suspension culture. Such suspension cells may then be subsequently isolated to be used directly as a final food product or a component ingredient of a food product (e.g., a hybrid food product including one or more further cell types and / or plant material). The starter cells may be primary cells directly obtained from an animal’s tissues, or continuous cell lines. In particular examples, the cells can be stem cells (e.g., embryonic stem cells, iPSCs, non-embryonic or somatic stem cells). If grown under the right conditions in appropriate culture media, primary cells will grow and proliferate, but only a finite number of times that is related to the telomere length at the end of the cell's DNA. Continuous cell lines, on the other hand, can be cultured in vitro over an extended period. After an appropriate period, the present method can further include the step of harvesting a meat product produced from culturing the non-human animal cells described herein. Suitably, the non-human animal cells are derived from any non-human animal species intended for human or non-human dietary consumption (e.g. cells of avian, ovine, caprine, porcine, bovine, piscine origin, such as cells of livestock, poultry, avian, game, or aquatic species). For some examples, the non-human animal cells are derived from livestock, such as domestic cattle, pigs, sheep, goats, camels, water buffalo, rabbits and the like. In other examples, the non-human animal cells are derived from poultry, such as domestic chicken, turkeys, ducks, geese, pigeons and the like. According to certain examples, the non-human animal cells are derived from game species such as wild deer, gallinaceous fowl, waterfowl, hare, rabbit and the like. In various examples, the non-human animal cells are from aquatic species or semi-aquatic species harvested commercially from wild fisheries or aquaculture operations, or for sport, including certain fish (e.g., a teleost species), crustaceans, molluscs, cephalopods, cetaceans, crocodilians, turtles, frogs and the like. In particular examples, the non-human animal cells are derived from a bovine animal or, more particularly, cattle. For other examples, the non-human animal cells are derived from a porcine animal or, more particularly, a domestic pig. According to various examples, the non- human animal cells are derived from a poultry animal or, more particularly, a chicken or a turkey. In some examples, the non-human animal cells are derived from a teleost animal, such as a salmon or tuna species. The culture media for culturing the non-human animal cells described herein suitably contains components necessary for cell proliferation, such as amino acids, salts, vitamins, growth factors, and buffering systems to control pH. Current methods typically add foetal bovine serum (FBS) or the like to the culture media prior to use as it provides vital macromolecules, growth factors, and immune molecules. It is contemplated, however, that the culture medium is suitably free or substantially free (e.g., less than about 1%, 0.5%, 0.1% or 0.05% by weight of the culture medium) of animal-derived components, such as animal-derived proteins. Moreover, it is envisaged, that the culture medium is suitably free or substantially free of serum. Similarly, the kit described herein suitably does not include serum. For the purposes of the present invention, the term “serum-free” means the absence of any measurable amounts of blood serum of any species including, but not limited to, the absence of foetal bovine serum, calf bovine serum, human serum, or the like, or combinations thereof. The term “substantially free of serum” means the culture medium is essentially free (e.g., less than about 1%, 0.5%, 0.1% or 0.05% by weight of the culture medium) of serum except as otherwise incidentally incorporated as a minor component (e.g., serum is present in a concentration less than about 1%, 0.5%, 0.1% or 0.05% by weight of the culture media). The culture medium may be a buffered solution containing components such as, but not limited to, inorganic salts (e.g., calcium chloride (CaCl2), potassium chloride (KCl), sodium chloride (NaCl), sodium bicarbonate (NaHCO3), sodium dihydrogen phosphate (NaH2PO4), magnesium sulfate (MgSO4), etc.), amino acids, vitamins (e.g., thiamine, riboflavin, folic acid, etc.), and other components, such as glucose, β-mercaptoethanol, ethylenediaminetetraacetic acid (EDTA) and sodium pyruvate. Suitably, the component protein, such as the transferrin protein, is of the same or similar species, such as from the same genus, to the non-human animal cells. A “similar species” may be one which comprises a component protein that demonstrates similarities with respect to the sequence, structure and / or function of the component protein in question. In particular examples, an amino acid sequence of a component protein of a first species that is similar to a second species demonstrates sequence similarity with an amino acid sequence of a component protein of the second species of at least about 50% (e.g., at least about 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or any range therein), more particularly at least about 55%, more particularly at least about 60%, more particularly at least about 65%, more particularly at least about 70%, more particularly at least about 75%, more particularly at least about 80%, more particularly at least about 85%, even more particularly at least about 90%, still even more particularly at least about 95% or yet even more particularly at least about 98% similarity therewith. According to particular examples, the component protein is of the same family to the non- human animal cells. For some examples, the component protein is of the same genus to the non- human animal cells. In certain examples, however, the component protein is of the same species to the non-human animal cells (e.g., both the component protein and the non-human animal cells are derived from a bovine species, a teleost species or a poultry species). It is expected that the component protein should then exert a higher bioactivity in relation to the non-human animal cells in culture compared to the use of a component protein, such as that derived from animal serum, of a genetically distant or distinct species to that of the non-human animal cells. Due to the enhanced compatibility, a reduced amount of growth factors, including the component protein, may be needed in the culture medium and improvements in overall cell growth may be observed. Suitably, the low purity extract of the component protein (e.g., the transferrin protein) of the above aspects is that hereinbefore described (e.g., produced by those methods described herein). So that preferred embodiments of the present disclosure may be fully understood and put into practical effect, reference is made to the following non-limiting examples. Examples Example 1. The aim of the present Example was to produce recombinant bovine transferrin (Uniprot Q29443, Bos taurus) by a plant, and more particularly a benth plant (Nicotiana benthamiana). Materials / Methods and Results Protein production in Nicotiana benthamiana A plasmid (SN750; SEQ ID NO: 13) for bovine transferrin protein expression in plant cells was constructed using a modular cloning system with the Golden Gate assembly protocols based on Type IIS restriction enzymes (Peccoud et al., 2011). DNA components were commercially synthesised by Thermo Fisher Scientific or Twist Bioscience. SN750 genetic construct (SEQ ID NO: 13) 1 tctgtgaaga caagcaagaa ttcaagcttg gaggtcaaca tggtggagca cgacactctg 61 gtctactcca aaaatgtcaa agatacagtc tcagaagatc aaagggctat tgagactttt 121 caacaaagga taatttcggg aaacctcctc ggattccatt gcccagctat ctgtcacttc 181 atcgaaagga cagtagaaaa ggaaggtggc tcctacaaat gccatcattg cgataaagga 241 aaggctatca ttcaagatct ctctgccgac agtggtccca aagatggacc cccacccacg 301 aggagcatcg tggaaaaaga agaggttcca accacgtcta caaagcaagt ggattgatgt 361 gataacatgg tggagcacga cactctggtc tactccaaaa atgtcaaaga tacagtctca 421 gaagatcaaa gggctattga gacttttcaa caaaggataa tttcgggaaa cctcctcgga 481 ttccattgcc cagctatctg tcacttcatc gaaaggacag tagaaaagga aggtggctcc 541 tacaaatgcc atcattgcga taaaggaaag gctatcattc aagatctctc tgccgacagt 601 ggtcccaaag atggaccccc acccacgagg agcatcgtgg aaaaagaaga ggttccaacc 661 acgtctacaa agcaagtgga ttgatgtgac atctccactg acgtaaggga tgacgcacaa 721 tcccactatc cttcgcaaga cccttcctct atataaggaa gttcatttca tttggagagg 781 acacgctcga gtataagagc tcatttttac aacaattacc aacaacaaca aacaacaaac 841 aacattacaa ttacatttac aattatcgat acaatggcct ctatcaacag gcctatcgtg 901 ttctttaccg tgtgcctgtt ccttctgtgc gacggttctc ttgctggagg tgatcctgag 961 agaactgttc ggtggtgcac tatttctacc cacgaggcta acaagtgcgc cagcttcaga 1021 gagaacgttt tgcggattct tgagagcggc cctttcgtgt cttgcgtgaa gaaaactagc 1081 cacatggact gcatcaaggc catctctaac aacgaggctg atgctgtgac tctggatggt 1141 ggtcttgttt acgaggctgg tctgaagcct aacaacctta agcctgttgt ggctgagttc 1201 cacggcacta aggataatcc tcagactcac tactacgctg tggccgtggt taagaaggat 1261 accgacttca agcttaacga gctgcggggt aagaagtctt gccatactgg tcttggtagg 1321 tccgctggtt ggaacattcc tatggccaag ctgtacaaag agctgcctga tccgcaagag 1381 tctattcaga gagctgctgc caacttcttc agcgcttctt gtgttccttg cgccgaccag 1441 tctagtttcc ctaagctttg tcagctgtgc gctggtaagg gtactgataa gtgcgcttgc 1501 tctaaccacg agccttactt cggttacagc ggtgctttca agtgcctgat ggaaggtgct 1561 ggtgatgtgg ctttcgtgaa gcactctacc gtgttcgaca acctgcctaa tcctgaggac 1621 cggaagaact acgagcttct gtgtggtgat aacacccgga agtccgtgga tgattaccaa 1681 gagtgctacc tggctatggt gccttctcat gctgttgttg ctaggaccgt tggtggcaaa 1741 gaggatgtta tttgggagct gctgaaccac gctcaagagc actttggaaa ggacaagcct 1801 gacaacttcc agctgttcca gtctcctcac ggtaaggatc tgctgttcaa ggatagcgct 1861 gatggcttcc tgaagatccc gagcaagatg gatttcgagc tgtacctggg ttacgagtac 1921 gttaccgctc tgcagaacct gagagagtct aagcctcctg acagctctaa ggatgagtgc 1981 atggttaagt ggtgcgctat cggtcatcaa gagcggacta agtgcgatag gtggtctggt 2041 ttttctggcg gtgctattga gtgtgagact gctgagaata ccgaagagtg cattgccaag 2101 atcatgaagg gcgaagctga cgctatgagc cttgatggtg gttacctgta cattgctggt 2161 aagtgcggtc ttgtgcctgt gcttgctgag aactataaga ctgagggcga gagctgcaag 2221 aacactcctg agaagggtta ccttgcagtc gccgttgtta agacctccga cgctaacatc 2281 aactggaaca acctgaagga caagaagagt tgccacaccg ctgttgatag aactgcaggc 2341 tggaatatcc ctatgggcct gctgtactcc aagatcaaca actgcaagtt cgacgagttc 2401 ttctctgctg gttgtgctcc tggttctccg aggaattctt ctctttgcgc tctgtgcatc 2461 ggctctgaga aaggtactgg gaaagagtgc gttccgaaca gcaatgagag gtactacgga 2521 tacactggcg ctttcagatg cctcgtggaa aagggtgatg tcgccttcgt taaggatcag 2581 accgtgatcc agaacaccga cggtaacaac aatgaggctt gggccaagaa cctgaagaaa 2641 gagaacttcg aggtcctgtg caaggacgga actagaaagc ctgttactga tgccgagaac 2701 tgccatttgg ctaggggtcc taatcatgct gtggtgagca gaaaggataa ggctacctgc 2761 gttgagaaga tcctgaacaa gcagcaggat gacttcggca agtctgtgac tgattgcacc 2821 agcaatttct gcctcttcca gagcaactct aaggaccttt tgttccggga tgacaccaag 2881 tgccttgcct ctatcgctaa gaaaacctac gacagctacc tgggcgacga ttatgttagg 2941 gctatgacca atctgcggca gtgctctacc tctaagcttc ttgaggcttg cactttccac 3001 aagcctggtg gctaccctta cgacgttcct gattacgctt gagcttaaag cagaatgctg 3061 agctaaaaga aaggcttttt ccattttcga gagacaatga gaaaagaaga agaagaagaa 3121 gaagaagaag aagaagaaaa gagtaaataa taaagcccca caggaggcga agttcttgta 3181 gctccatgtt atctaagtta ttgatattgt ttgccctata ttttatttct gtcattgtgt 3241 atgttttgtt cagtttcgat ctccttgcaa aatgcagaga ttatgagatg aataaactaa 3301 gttatattat tatacgtgtt aatattctcc tcctctctct agctagcctt ttgttttctc 3361 tttttcttat ttgattttct ttaaatcaat ccattttagg agagggccag ggagtgatcc 3421 agcaaaacat gaagattaga agaaacttcc ctcttttttt tcctgaaaac aatttaacgt 3481 cgagatttat ctctttttgt aatggaatca tttctacagt tatgacgtcc gcaaaaatca 3541 ccagtctctc tctacaaatc tatctctctc tatttttctc cagaataatg tgtgagtagt 3601 tcccagataa gggaattagg gttcttatag ggtttcgctc atgtgttgag catataagaa 3661 acccttagta tgtatttgta tttgtaaaat acttctatca ataaaatttc taattcctaa 3721 aaccaaaatc cagtgactaa tcataatagc tttaatattt caagatatta ttaagttaac 3781 gttgtcaata tcctggaaat tttgcaaaat gaatcaagcc tatatggctg taatatgaat 3841 ttaaaagcag ctcgatgtgg tggtaatatg taatttactt gattctaaaa aaatatccca 3901 agtattaata atttctgcta ggaagaaggt tagctacgat ttacagcaaa gccagaatac 3961 aaagaaccat aaagtgattg aagctcgaaa tatacgaagg aacaaatatt tttaaaaaaa 4021 tacgcaatga cttggaacaa aagaaagtga tatatttttt gttcttaaac aagcatcccc 4081 tctaaagaat ggcagttttc ctttgcatgt aactattatg ctcccttcgt tacaaaaatt 4141 ttggactact attgggaact tcttctgaaa atagtgcgct actattgtct tctgcacgaa 4201 gtggtttaaa ctatcagtgt ttgacaggat atattggcgg gtaaacctaa gagaaaagag 4261 cgtttattag aataatcgga tatttaaaag ggcgtgaaaa ggtttatccg ttcgtccatt 4321 tgtatgtgca tgccaaccac agggttcccc agatcaggcg ctggctgctg aacccccagc 4381 cggaactgac cccacaaggc cctagcgttt gcaatgcacc aggtcatcat tgacccaggc 4441 gtgttccacc aggccgctgc ctcgcaactc ttcgcaggct tcgccgacct gctcgcgcca 4501 cttcttcacg cgggtggaat ccgatccgca catgaggcgg aaggtttcca gcttgagcgg 4561 gtacggctcc cggtgcgagc tgaaatagtc gaacatccgt cgggccgtcg gcgacagctt 4621 gcggtacttc tcccatatga atttcgtgta gtggtcgcca gcaaacagca cgacgatttc 4681 ctcgtcgatc aggacctggc aacgggacgt tttcttgcca cggtccagga cgcggaagcg 4741 gtgcagcagc gacaccgatt ccaggtgccc aacgcggtcg gacgtgaagc ccatcgccgt 4801 cgcctgtagg cgcgacaggc attcctcggc cttcgtgtaa taccggccat tgatcgacca 4861 gcccaggtcc tggcaaagct cgtagaacgt gaaggtgatc ggctcgccga taggggtgcg 4921 cttcgcgtac tccaacacct gctgccacac cagttcgtca tcgtcggccc gcagctcgac 4981 gccggtgtag gtgatcttca cgtccttgtt gacgtggaaa atgaccttgt tttgcagcgc 5041 ctcgcgcggg attttcttgt tgcgcgtggt gaacagggca gagcgggccg tgtcgtttgg 5101 catcgctcgc atcgtgtccg gccacggcgc aatatcgaac aaggaaagct gcatttcctt 5161 gatctgctgc ttcgtgtgtt tcagcaacgc ggcctgcttg gcctcgctga cctgttttgc 5221 caggtcctcg ccggcggttt ttcgcttctt ggtcgtcata gttcctcgcg tgtcgatggt 5281 catcgacttc gccaaacctg ccgcctcctg ttcaagacga cgcgaacgct ccacggcggc 5341 cgatggcgcg ggcagggcag ggggagccag ttgcacgctg tcgcgctcga tcttggccgt 5401 agcttgctgg accatcgagc cgacggactg gaaggtttcg cggggcgcac gcatgacggt 5461 gcggcttgcg atggtttcgg catcctcggc ggaaaacccc gcgtcgatca gttcttgcct 5521 gtatgccttc cggtcaaacg tccgattcat tcaccctcct tgcgggattg ccccgactca 5581 cgccggggca atgtgccctt attcctgatt tgacccgcct ggtgccttgg tgtccagata 5641 atccacctta tcggcaatga agtcggtccc gtagaccgtc tggccgtcct tctcgtactt 5701 ggtattccga atcttgccct gcacgaatac cagcgacccc ttgcccaaat acttgccgtg 5761 ggcctcggcc tgagagccaa aacacttgat gcggaagaag tcggtgcgct cctgcttgtc 5821 gccggcatcg ttgcgccaca tctaggatct gccaggaacc gtaaaaaggc cgcgttgctg 5881 gcgtttttcc ataggctccg cccccctgac gagcatcaca aaaatcgacg ctcaagtcag 5941 aggtggcgaa acccgacagg actataaaga taccaggcgt ttccccctgg aagctccctc 6001 gtgcgctctc ctgttccgac cctgccgctt accggatacc tgtccgcctt tctcccttcg 6061 ggaagcgtgg cgctttctca tagctcacgc tgtaggtatc tcagttcggt gtaggtcgtt 6121 cgctccaagc tgggctgtgt gcacgaaccc cccgttcagc ccgaccgctg cgccttatcc 6181 ggtaactatc gtcttgagtc caacccggta agacacgact tatcgccact ggcagcagcc 6241 actggtaaca ggattagcag agcgaggtat gtaggcggtg ctacagagtt cttgaagtgg 6301 tggcctaact acggctacac tagaaggaca gtatttggta tctgcgctct gctgaagcca 6361 gttaccttcg gaaaaagagt tggtagctct tgatccggca aacaaaccac cgctggtagc 6421 ggtggttttt ttgtttgcaa gcagcagatt acgcgcagaa aaaaaggatc tcaagaagat 6481 cctttgatct tttctacggg gtctgacgct cagtggaacg aaaactcacg ttaagggatt 6541 ttggtcatga gattatcaaa aaggatcttc acctagatcc ttttaaatta aaaatgaagt 6601 tttaaatcaa tctaaagtat atatgagtaa acttggtctg acagttacca atgcttaatc 6661 agtgaggcac ctatctcagc gatctgtcta tttcgttcat ccatagttgc ctgactcccc 6721 gtcgtgtaga taactacgat acgggagggc ttaccatctg gccccagtgc tgcaatgata 6781 ccgcgagaac cacgctcacc ggctccagat ttatcagcaa taaaccagcc agccggaagg 6841 gccgagcgca gaagtggtcc tgcaacttta tccgcctcca tccagtctat taattgttgc 6901 cgggaagcta gagtaagtag ttcgccagtt aatagtttgc gcaacgttgt tgccattgct 6961 acaggcatcg tggtgtcacg ctcgtcgttt ggtatggctt cattcagctc cggttcccaa 7021 cgatcaaggc gagttacatg atcccccatg ttgtgcaaaa aagcggttag ctccttcggt 7081 cctccgatcg ttgtcagaag taagttggcc gcagtgttat cactcatggt tatggcagca 7141 ctgcataatt ctcttactgt catgccatcc gtaagatgct tttctgtgac tggtgagtac 7201 tcaaccaagt cattctgaga atagtgtatg cggcgaccga gttgctcttg cccggcgtca 7261 atacgggata ataccgcgcc acatagcaga actttaaaag tgctcatcat tggaaaacgt 7321 tcttcggggc gaaaactctc aaggatctta ccgctgttga gatccagttc gatgtaaccc 7381 actcgtgcac ccaactgatc ttcagcatct tttactttca ccagcgtttc tgggtgagca 7441 aaaacaggaa ggcaaaatgc cgcaaaaaag ggaataaggg cgacacggaa atgttgaata 7501 ctcatactct tcctttttca atattattga agcatttatc agggttattg tctcatgagc 7561 ggatacatat ttgaatgtat ttagaaaaat aaacaaatag gggttccgcg cacgaattgg 7621 ccagcgctgc catttttggg gtgaggccgt tcgcggccga ggggcgcagc ccctgggggg 7681 atgggaggcc cgcgttagcg ggccgggagg gttcgagaag ggggggcacc ccccttcggc 7741 gtgcgcggtc acgcgcacag ggcgcagccc tggttaaaaa caaggtttat aaatattggt 7801 ttaaaagcag gttaaaagac aggttagcgg tggccgaaaa acgggcggaa acccttgcaa 7861 atgctggatt ttctgcctgt ggacagcccc tcaaatgtca ataggtgcgc ccctcatctg 7921 tcagcactct gcccctcaag tgtcaaggat cgcgcccctc atctgtcagt agtcgcgccc 7981 ctcaagtgtc aataccgcag ggcacttatc cccaggcttg tccacatcat ctgtgggaaa 8041 ctcgcgtaaa atcaggcgtt ttcgccgatt tgcgaggctg gccagctcca cgtcgccggc 8101 cgaaatcgag cctgcccctc atctgtcaac gccgcgccgg gtgagtcggc ccctcaagtg 8161 tcaacgtccg cccctcatct gtcagtgagg gccaagtttt ccgcgaggta tccacaacgc 8221 cggcggccgc ggtgtctcgc acacggcttc gacggcgttt ctggcgcgtt tgcagggcca 8281 tagacggccg ccagcccagc ggcgagggca accagcccgg tgagcgtcgc aaaggagatc 8341 ctgatctgac tgatgggctg cctgtatcga gtggtgattt tgtgccgagc tgccggtcgg 8401 ggagctgttg gctggctggt ggcaggatat attgtggtgt aaacaaattg acgcttagac 8461 aacttaataa cacattgcgg acgtttttaa tgtactgggg tggatgcagt gggccccac Expression cassette of SN750 genetic construct (SEQ ID NO: 14) g gaggtcaaca tggtggagca cgacactctg gtctactcca aaaatgtcaa agatacagtc tcagaagatc aaagggctat tgagactttt caacaaagga taatttcggg aaacctcctc ggattccatt gcccagctat ctgtcacttc atcgaaagga cagtagaaaa ggaaggtggc tcctacaaat gccatcattg cgataaagga aaggctatca ttcaagatct ctctgccgac agtggtccca aagatggacc cccacccacg aggagcatcg tggaaaaaga agaggttcca accacgtcta caaagcaagt ggattgatgt gataacatgg tggagcacga cactctggtc tactccaaaa atgtcaaaga tacagtctca gaagatcaaa gggctattga gacttttcaa caaaggataa tttcgggaaa cctcctcgga ttccattgcc cagctatctg tcacttcatc gaaaggacag tagaaaagga aggtggctcc tacaaatgcc atcattgcga taaaggaaag gctatcattc aagatctctc tgccgacagt ggtcccaaag atggaccccc acccacgagg agcatcgtgg aaaaagaaga ggttccaacc acgtctacaa agcaagtgga ttgatgtgac atctccactg acgtaaggga tgacgcacaa tcccactatc cttcgcaaga cccttcctct atataaggaa gttcatttca tttggagagg acacgctcga gtataagagc tcatttttac aacaattacc aacaacaaca aacaacaaac aacattacaa ttacatttac aattatcgat acaatggcct ctatcaacag gcctatcgtg ttctttaccg tgtgcctgtt ccttctgtgc gacggttctc ttgctggagg tgatcctgag agaactgttc ggtggtgcac tatttctacc cacgaggcta acaagtgcgc cagcttcaga gagaacgttt tgcggattct tgagagcggc cctttcgtgt cttgcgtgaa gaaaactagc cacatggact gcatcaaggc catctctaac aacgaggctg atgctgtgac tctggatggt ggtcttgttt acgaggctgg tctgaagcct aacaacctta agcctgttgt ggctgagttc cacggcacta aggataatcc tcagactcac tactacgctg tggccgtggt taagaaggat accgacttca agcttaacga gctgcggggt aagaagtctt gccatactgg tcttggtagg tccgctggtt ggaacattcc tatggccaag ctgtacaaag agctgcctga tccgcaagag tctattcaga gagctgctgc caacttcttc agcgcttctt gtgttccttg cgccgaccag tctagtttcc ctaagctttg tcagctgtgc gctggtaagg gtactgataa gtgcgcttgc tctaaccacg agccttactt cggttacagc ggtgctttca agtgcctgat ggaaggtgct ggtgatgtgg ctttcgtgaa gcactctacc gtgttcgaca acctgcctaa tcctgaggac cggaagaact acgagcttct gtgtggtgat aacacccgga agtccgtgga tgattaccaa gagtgctacc tggctatggt gccttctcat gctgttgttg ctaggaccgt tggtggcaaa gaggatgtta tttgggagct gctgaaccac gctcaagagc actttggaaa ggacaagcct gacaacttcc agctgttcca gtctcctcac ggtaaggatc tgctgttcaa ggatagcgct gatggcttcc tgaagatccc gagcaagatg gatttcgagc tgtacctggg ttacgagtac gttaccgctc tgcagaacct gagagagtct aagcctcctg acagctctaa ggatgagtgc atggttaagt ggtgcgctat cggtcatcaa gagcggacta agtgcgatag gtggtctggt ttttctggcg gtgctattga gtgtgagact gctgagaata ccgaagagtg cattgccaag atcatgaagg gcgaagctga cgctatgagc cttgatggtg gttacctgta cattgctggt aagtgcggtc ttgtgcctgt gcttgctgag aactataaga ctgagggcga gagctgcaag aacactcctg agaagggtta ccttgcagtc gccgttgtta agacctccga cgctaacatc aactggaaca acctgaagga caagaagagt tgccacaccg ctgttgatag aactgcaggc tggaatatcc ctatgggcct gctgtactcc aagatcaaca actgcaagtt cgacgagttc ttctctgctg gttgtgctcc tggttctccg aggaattctt ctctttgcgc tctgtgcatc ggctctgaga aaggtactgg gaaagagtgc gttccgaaca gcaatgagag gtactacgga tacactggcg ctttcagatg cctcgtggaa aagggtgatg tcgccttcgt taaggatcag accgtgatcc agaacaccga cggtaacaac aatgaggctt gggccaagaa cctgaagaaa gagaacttcg aggtcctgtg caaggacgga actagaaagc ctgttactga tgccgagaac tgccatttgg ctaggggtcc taatcatgct gtggtgagca gaaaggataa ggctacctgc gttgagaaga tcctgaacaa gcagcaggat gacttcggca agtctgtgac tgattgcacc agcaatttct gcctcttcca gagcaactct aaggaccttt tgttccggga tgacaccaag tgccttgcct ctatcgctaa gaaaacctac gacagctacc tgggcgacga ttatgttagg gctatgacca atctgcggca gtgctctacc tctaagcttc ttgaggcttg cactttccac aagcctggtg gctaccctta cgacgttcct gattacgctt gagcttaaag cagaatgctg agctaaaaga aaggcttttt ccattttcga gagacaatga gaaaagaaga agaagaagaa gaagaagaag aagaagaaaa gagtaaataa taaagcccca caggaggcga agttcttgta gctccatgtt atctaagtta ttgatattgt ttgccctata ttttatttct gtcattgtgt atgttttgtt cagtttcgat ctccttgcaa aatgcagaga ttatgagatg aataaactaa gttatattat tatacgtgtt aatattctcc tcctctctct agctagcctt ttgttttctc tttttcttat ttgattttct ttaaatcaat ccattttagg agagggccag ggagtgatcc agcaaaacat gaagattaga agaaacttcc ctcttttttt tcctgaaaac aatttaacgt cgagatttat ctctttttgt aatggaatca tttctacagt tatgacgtcc gcaaaaatca ccagtctctc tctacaaatc tatctctctc tatttttctc cagaataatg tgtgagtagt tcccagataa gggaattagg gttcttatag ggtttcgctc atgtgttgag catataagaa acccttagta tgtatttgta tttgtaaaat acttctatca ataaaatttc taattcctaa aaccaaaatc cagtgactaa tcataatagc tttaatattt caagatatta ttaagttaac gttgtcaata tcctggaaat tttgcaaaat gaatcaagcc tatatggctg taatatgaat ttaaaagcag ctcgatgtgg tggtaatatg taatttactt gattctaaaa aaatatccca agtattaata atttctgcta ggaagaaggt tagctacgat ttacagcaaa gccagaatac aaagaaccat aaagtgattg aagctcgaaa tatacgaagg aacaaatatt tttaaaaaaa tacgcaatga cttggaacaa aagaaagtga tatatttttt gttcttaaac aagcatcccc tctaaagaat ggcagttttc ctttgcatgt aactattatg ctcccttcgt tacaaaaatt ttggactact attgggaact tcttctgaaa atagtgcgct 5’ UTR of SN750 construct (SEQ ID NO: 15) gtcaacatggtggagcacgacactctggtctactccaaaaatgtcaaagatacagtctcagaagatcaaagggctat tgagacttttcaacaaaggataatttcgggaaacctcctcggattccattgcccagctatctgtcacttcatcgaaa ggacagtagaaaaggaaggtggctcctacaaatgccatcattgcgataaaggaaaggctatcattcaagatctctct gccgacagtggtcccaaagatggacccccacccacgaggagcatcgtggaaaaagaagaggttccaaccacgtctac aaagcaagtggattgatgtgataacatggtggagcacgacactctggtctactccaaaaatgtcaaagatacagtct cagaagatcaaagggctattgagacttttcaacaaaggataatttcgggaaacctcctcggattccattgcccagct atctgtcacttcatcgaaaggacagtagaaaaggaaggtggctcctacaaatgccatcattgcgataaaggaaaggc tatcattcaagatctctctgccgacagtggtcccaaagatggacccccacccacgaggagcatcgtggaaaaagaag aggttccaaccacgtctacaaagcaagtggattgatgtgacatctccactgacgtaagggatgacgcacaatcccac tatccttcgcaagacccttcctctatataaggaagttcatttcatttggagaggacacgctcgagtataagagctca tttttacaacaattaccaacaacaacaaacaacaaacaacattacaattacatttacaattatcgatac GT1 signal sequence of SN750 construct (SEQ ID NO: 16) atggcctctatcaacaggcctatcgtgttctttaccgtgtgcctgttccttctgtgcgacggttctcttgct 3’ UTR / Terminator sequence of SN750 construct (SEQ ID NO: 17) gcttaaagcagaatgctgagctaaaagaaaggctttttccattttcgagagacaatgagaaaagaagaagaagaaga agaagaagaagaagaagaaaagagtaaataataaagccccacaggaggcgaagttcttgtagctccatgttatctaa gttattgatattgtttgccctatattttatttctgtcattgtgtatgttttgttcagtttcgatctccttgcaaaat gcagagattatgagatgaataaactaagttatattattatacgtgttaatattctcctcctctctctagctagcctt ttgttttctctttttcttatttgattttctttaaatcaatccattttaggagagggccagggagtgatccagcaaaa catgaagattagaagaaacttccctcttttttttcctgaaaacaatttaacgtcgagatttatctctttttgtaatg gaatcatttctacagttatgacgtccgcaaaaatcaccagtctctctctacaaatctatctctctctatttttctcc agaataatgtgtgagtagttcccagataagggaattagggttcttatagggtttcgctcatgtgttgagcatataag aaacccttagtatgtatttgtatttgtaaaatacttctatcaataaaatttctaattcctaaaaccaaaatccagtg actaatcataatagctttaatatttcaagatattattaagttaacgttgtcaatatcctggaaattttgcaaaatga atcaagcctatatggctgtaatatgaatttaaaagcagctcgatgtggtggtaatatgtaatttacttgattctaaa aaaatatcccaagtattaataatttctgctaggaagaaggttagctacgatttacagcaaagccagaatacaaagaa ccataaagtgattgaagctcgaaatatacgaaggaacaaatatttttaaaaaaatacgcaatgacttggaacaaaag aaagtgatatattttttgttcttaaacaagcatcccctctaaagaatggcagttttcctttgcatgtaactattatg ctcccttcgttacaaaaattttggactactattgggaacttcttctgaaaatagtgcgct The sequence for the SN750 genetic construct utilised for the present Example is provided in SEQ ID NO: 13. The expression cassette of the SN750 construct is also provided in SEQ ID NO: 14. The construct used a regulatory cassette that included two CaMV 35S promoters with a TMV 5’UTR (SEQ ID NO: 15) and a hybrid UTR / terminator region including the intronless tobacco extensin 3’ UTR, a 35S terminator and a minimal matrix attachment (MARS) region (SEQ ID NO: 17). The Bovine transferrin gene was commercially synthesised using a plant-derived codon bias for optimised expression, and sequences were designed to allow translational fusions at the N- and / or C-terminus. N-terminal and C-terminal translational fusion extensions allowed targeting of proteins to the endoplasmic reticulum ER (SN750). For ER targeting, the rice seed storage protein glutelin 1 (GT1) signal peptide (EN38702) (SEQ ID NO: 16) was used. Constructs were assembled into a backbone L1-acceptor vector, which includes standard T-DNA based flanking regions using Type IIS restriction cloning with the BsaI enzyme for Golden Gate construction. Five week old plants of the species Nicotiana benthamiana were infused with this construct, as per the method described in Allen et al. (2020, PNAS, 117 (37) 23165-23173). Leaves of the transiently transfected benth plants were subsequently harvested 3 to 5 days after infusion to extract proteins from. Protein extraction from Nicotiana benthamiana For protein extraction, the following protocol was used. 1: Obtaining low-purity transferrin ^ The plant material was homogenised and added to an extraction buffer (25mM Tris- HCl of pH 7.5). ^ The samples were left at room temp and shaken for 30min ^ After extraction, all samples were centrifuged at 13K for 20min at RT. Multiple rounds of centrifugation may be used to remove cellular debris. ^ Supernatant were assayed to estimate total soluble protein (TS) and protein content. ^ The supernatant was dialysed using a dialysis kit (Slide-A-Lyzer™; ThermoFisher) ^ For the dialysis step, the supernatant was passed through a 10 kDa or 30 kDa filter or used directly without any further purification steps ^ Enzymes (amylase / cellulase) may optionally be used to degrade sugars, carbohydrates, cell walls etc and achieve a higher protein content in the extract Transferrin characterisation and quantification A targeted multiple reaction monitoring approach (LC-MRM-MS) was developed to enable the quantification of transferrin in the supernatant extracted from the plant material. Briefly, proteins were extracted from the supernatant using 8M urea and were then reduced with DTT and alkylated with iodoacetamide. The linearized alkylated and reduced proteins were then tryptically digested and eluted using a 10 kDa cut off filter. The peptides were lyophilised and resuspended in 0.1% formic acid and then analysed via LC-MRM-MS using an optimised protocol. Figure 1 shows the sum of the areas under the peak for the 4 most abundant MS / MS transitions of transferrin specific peptides for different colonies of the transformed strain. These LC-MS results clearly confirm the presence of transferrin in the plant extracts transfected with construct SN750. Moreover, a matrix matched calibration curve was created to quantify transferrin protein in the plant extract and it was determined that ~21% of the total protein content and 4% by weight of the extract was transferrin (Figure 2). That equates to approximately 0.23% of the wet weight of the leaves being transferrin. Western blot analysis further confirmed the presence of transferrin protein (i.e., a protein band of ~80 kDa molecular weight) in the plant extract when the SN750 construct is used (Figure 3). Example 2 This Example was designed to determine if highly concentrated and functional bovine transferrin could be extracted from plant cells. For this, a Streptactin tagging method, which enables high sensitivity and high yield enrichment of expressed proteins, was utilised. Accordingly, a plant expression construct (SN772 construct) was designed to produce a synthetic protein comprising a GT1 targeting peptide fused to the N terminus of bovine transferrin, as described for the SN750 construct in Example 1, with a C-terminal twin-strep tag (Schmidt et al., 2013). The present inventors also wanted to predict if the twin-strep tag C-terminal fusion may inhibit function of the transferrin protein. For this purpose, the alphafold program was used to model any structural or steric implications of the tag when fused at the C-terminus of the transferrin protein. It was found that the C-terminal tag was predicted to not interfere with function of the synthetic protein, and particularly not interfere with binding to the transferrin receptor complex (Figure 5). Next, the SN772 construct was transformed in Agrobacterium cells and then co-infiltrated into N. benthamiana leaves with a P19 construct to prevent transgene silencing. Five days post infiltration, 110 grams of plant material was harvested and ground in 150 mL of lysis buffer (100mM Tris, 200mM NaCl, 10% glycerol, 10uM Leupetin, 0.2mM phenylmethylsulfonyl fluoride pH 8.6). The mixture was filtered using miracloth, then ultracentrifuged at 4oC for 1.5 hours at 30,000g. The supernatant was applied to a streptactin XT cartridge and bound at 2ml / min. Afterwards, the column was washed with 50 mL wash buffer (100 mM Tris, 200 mM NaCl, 10% glycerol), and eluted with wash buffer + 50mM biotin in a volume of 10 mL, then concentrated to 500 uL with a 30 kDa filter. The size and abundance of the streptactin-purified transferrin protein from the SN772 construct-infiltrated plants was then assessed. For this, Total (T), Input (IP), Pellet (P), Flow through (FT) and Eluate (E) fractions were run on a gel and protein abundance and purity were assessed by Coomassie staining and anti-streptactin western blotting (Figure 6). It was found that the eluate sample produced a strong predominant band by western blot and in the Coomassie gel at the expected size for the recombinant transferrin protein, with some minor upper and lower bands that could represent other proteins, concatemers or degradation products. The concentration of the eluate sample was determined to be 10 mg / mL. The plant extract containing transferrin was then quantified using LC-MRM-MS and utilised in cell culture with C2C12 myoblast cells. In brief, C2C12 cells were supplemented with the plant-produced transferrin at different concentrations (40, 20 and 10 ug / mL media) and compared with the growth of control C2C12 cells cultured in 10% FBS or B9 supplemented media at days 3, 4, 5, 6 and 7 of culture. Figure 4 clearly demonstrates a dose response curve with an increase in cell growth of the C2C12 cells in line with an increasing transferrin concentration. The 20 and 40 ug / mL transferrin-supplemented C2C12 cells also grew significantly better than those cells cultured in the TF negative B9 (serum free)-supplemented media and in traditional DMEM with FBS (10%) (Figure 4). This result demonstrates the functionality of the non-human transferrin derived from benth plants of this Example. SN772 genetic construct (SEQ ID NO: 22) FEATURES Location / Qualifiers misc_feature 30..876 / Source="referenceToDocument: urn:local:gre507:15- d8x89ir" / label="pICH51288 (concatenated sequence 2)" / note="Geneious type: Concatenated sequence" ligation 30..33 / label="Ligation" misc_feature complement(30..33) / label="GGAG fusion site" misc_feature 34..786 / label="2x35S pro" / note="Geneious type: promoter uukaryotic" 5'UTR 803..864 / label="Omega leader" misc_feature 873..951 / Source="referenceToDocument: urn:local:hus029:r- fo2mab4" / modified_by="all237" / label="EN38669 rice GT1 peptide" / note="Geneious type: Concatenated sequence" ligation 873..876 / label="Ligation" Misc._feature 874..3099 / created_by="all237" / label="GT1:TfBv:TwinStrep" misc_feature 948..3010 / Source="referenceToDocument: urn:local:hus029:p- fo2m74o" / modified_by="all237" / label="Bovine Transferrin" / note="Geneious type: Concatenated sequence" ligation 948..951 / label="Ligation" misc_feature 3007..3103 / Source="referenceToDocument: urn:local:hus029:239-dlx1tew" / label="EN38128 C-term streptag (concatenated sequence 5)" / note="Geneious type: Concatenated sequence" ligation 3007..3010 / label="Ligation" misc_feature 3100..4237 / Source="referenceToDocument: urn:local:hus029:n- fo2m2lg" / modified_by="all237" / label="EN38588 hybrid terminator" / note="Geneious type: Concatenated sequence" ligation 3100..3103 / label="Ligation" misc_feature 4234..33 / Source="referenceToDocument: urn:local:gre507:2o- d8x89it" / label="EC47742\pL1V-F2 (concatenated sequence 1) (reversed)" 1 tctgtgaaga caagcaagaa ttcaagcttg gaggtcaaca tggtggagca cgacactctg 61 gtctactcca aaaatgtcaa agatacagtc tcagaagatc aaagggctat tgagactttt 121 caacaaagga taatttcggg aaacctcctc ggattccatt gcccagctat ctgtcacttc 181 atcgaaagga cagtagaaaa ggaaggtggc tcctacaaat gccatcattg cgataaagga 241 aaggctatca ttcaagatct ctctgccgac agtggtccca aagatggacc cccacccacg 301 aggagcatcg tggaaaaaga agaggttcca accacgtcta caaagcaagt ggattgatgt 361 gataacatgg tggagcacga cactctggtc tactccaaaa atgtcaaaga tacagtctca 421 gaagatcaaa gggctattga gacttttcaa caaaggataa tttcgggaaa cctcctcgga 481 ttccattgcc cagctatctg tcacttcatc gaaaggacag tagaaaagga aggtggctcc 541 tacaaatgcc atcattgcga taaaggaaag gctatcattc aagatctctc tgccgacagt 601 ggtcccaaag atggaccccc acccacgagg agcatcgtgg aaaaagaaga ggttccaacc 661 acgtctacaa agcaagtgga ttgatgtgac atctccactg acgtaaggga tgacgcacaa 721 tcccactatc cttcgcaaga cccttcctct atataaggaa gttcatttca tttggagagg 781 acacgctcga gtataagagc tcatttttac aacaattacc aacaacaaca aacaacaaac 841 aacattacaa ttacatttac aattatcgat acaatggcct ctatcaacag gcctatcgtg 901 ttctttaccg tgtgcctgtt ccttctgtgc gacggttctc ttgctggagg tgatcctgag 961 agaactgttc ggtggtgcac tatttctacc cacgaggcta acaagtgcgc cagcttcaga 1021 gagaacgttt tgcggattct tgagagcggc cctttcgtgt cttgcgtgaa gaaaactagc 1081 cacatggact gcatcaaggc catctctaac aacgaggctg atgctgtgac tctggatggt 1141 ggtcttgttt acgaggctgg tctgaagcct aacaacctta agcctgttgt ggctgagttc 1201 cacggcacta aggataatcc tcagactcac tactacgctg tggccgtggt taagaaggat 1261 accgacttca agcttaacga gctgcggggt aagaagtctt gccatactgg tcttggtagg 1321 tccgctggtt ggaacattcc tatggccaag ctgtacaaag agctgcctga tccgcaagag 1381 tctattcaga gagctgctgc caacttcttc agcgcttctt gtgttccttg cgccgaccag 1441 tctagtttcc ctaagctttg tcagctgtgc gctggtaagg gtactgataa gtgcgcttgc 1501 tctaaccacg agccttactt cggttacagc ggtgctttca agtgcctgat ggaaggtgct 1561 ggtgatgtgg ctttcgtgaa gcactctacc gtgttcgaca acctgcctaa tcctgaggac 1621 cggaagaact acgagcttct gtgtggtgat aacacccgga agtccgtgga tgattaccaa 1681 gagtgctacc tggctatggt gccttctcat gctgttgttg ctaggaccgt tggtggcaaa 1741 gaggatgtta tttgggagct gctgaaccac gctcaagagc actttggaaa ggacaagcct 1801 gacaacttcc agctgttcca gtctcctcac ggtaaggatc tgctgttcaa ggatagcgct 1861 gatggcttcc tgaagatccc gagcaagatg gatttcgagc tgtacctggg ttacgagtac 1921 gttaccgctc tgcagaacct gagagagtct aagcctcctg acagctctaa ggatgagtgc 1981 atggttaagt ggtgcgctat cggtcatcaa gagcggacta agtgcgatag gtggtctggt 2041 ttttctggcg gtgctattga gtgtgagact gctgagaata ccgaagagtg cattgccaag 2101 atcatgaagg gcgaagctga cgctatgagc cttgatggtg gttacctgta cattgctggt 2161 aagtgcggtc ttgtgcctgt gcttgctgag aactataaga ctgagggcga gagctgcaag 2221 aacactcctg agaagggtta ccttgcagtc gccgttgtta agacctccga cgctaacatc 2281 aactggaaca acctgaagga caagaagagt tgccacaccg ctgttgatag aactgcaggc 2341 tggaatatcc ctatgggcct gctgtactcc aagatcaaca actgcaagtt cgacgagttc 2401 ttctctgctg gttgtgctcc tggttctccg aggaattctt ctctttgcgc tctgtgcatc 2461 ggctctgaga aaggtactgg gaaagagtgc gttccgaaca gcaatgagag gtactacgga 2521 tacactggcg ctttcagatg cctcgtggaa aagggtgatg tcgccttcgt taaggatcag 2581 accgtgatcc agaacaccga cggtaacaac aatgaggctt gggccaagaa cctgaagaaa 2641 gagaacttcg aggtcctgtg caaggacgga actagaaagc ctgttactga tgccgagaac 2701 tgccatttgg ctaggggtcc taatcatgct gtggtgagca gaaaggataa ggctacctgc 2761 gttgagaaga tcctgaacaa gcagcaggat gacttcggca agtctgtgac tgattgcacc 2821 agcaatttct gcctcttcca gagcaactct aaggaccttt tgttccggga tgacaccaag 2881 tgccttgcct ctatcgctaa gaaaacctac gacagctacc tgggcgacga ttatgttagg 2941 gctatgacca atctgcggca gtgctctacc tctaagcttc ttgaggcttg cactttccac 3001 aagcctggtg gctggagtca tcctcagttt gagaaaggtg gaggttcagg tggtggaagc 3061 ggtggatctg cttggtcaca tccacaattt gaaaaatgag cttaaagcag aatgctgagc 3121 taaaagaaag gctttttcca ttttcgagag acaatgagaa aagaagaaga agaagaagaa 3181 gaagaagaag aagaaaagag taaataataa agccccacag gaggcgaagt tcttgtagct 3241 ccatgttatc taagttattg atattgtttg ccctatattt tatttctgtc attgtgtatg 3301 ttttgttcag tttcgatctc cttgcaaaat gcagagatta tgagatgaat aaactaagtt 3361 atattattat acgtgttaat attctcctcc tctctctagc tagccttttg ttttctcttt 3421 ttcttatttg attttcttta aatcaatcca ttttaggaga gggccaggga gtgatccagc 3481 aaaacatgaa gattagaaga aacttccctc ttttttttcc tgaaaacaat ttaacgtcga 3541 gatttatctc tttttgtaat ggaatcattt ctacagttat gacgtccgca aaaatcacca 3601 gtctctctct acaaatctat ctctctctat ttttctccag aataatgtgt gagtagttcc 3661 cagataaggg aattagggtt cttatagggt ttcgctcatg tgttgagcat ataagaaacc 3721 cttagtatgt atttgtattt gtaaaatact tctatcaata aaatttctaa ttcctaaaac 3781 caaaatccag tgactaatca taatagcttt aatatttcaa gatattatta agttaacgtt 3841 gtcaatatcc tggaaatttt gcaaaatgaa tcaagcctat atggctgtaa tatgaattta 3901 aaagcagctc gatgtggtgg taatatgtaa tttacttgat tctaaaaaaa tatcccaagt 3961 attaataatt tctgctagga agaaggttag ctacgattta cagcaaagcc agaatacaaa 4021 gaaccataaa gtgattgaag ctcgaaatat acgaaggaac aaatattttt aaaaaaatac 4081 gcaatgactt ggaacaaaag aaagtgatat attttttgtt cttaaacaag catcccctct 4141 aaagaatggc agttttcctt tgcatgtaac tattatgctc ccttcgttac aaaaattttg 4201 gactactatt gggaacttct tctgaaaata gtgcgctact attgtcttct gcacgaagtg 4261 gtttaaacta tcagtgtttg acaggatata ttggcgggta aacctaagag aaaagagcgt 4321 ttattagaat aatcggatat ttaaaagggc gtgaaaaggt ttatccgttc gtccatttgt 4381 atgtgcatgc caaccacagg gttccccaga tcaggcgctg gctgctgaac ccccagccgg 4441 aactgacccc acaaggccct agcgtttgca atgcaccagg tcatcattga cccaggcgtg 4501 ttccaccagg ccgctgcctc gcaactcttc gcaggcttcg ccgacctgct cgcgccactt 4561 cttcacgcgg gtggaatccg atccgcacat gaggcggaag gtttccagct tgagcgggta 4621 cggctcccgg tgcgagctga aatagtcgaa catccgtcgg gccgtcggcg acagcttgcg 4681 gtacttctcc catatgaatt tcgtgtagtg gtcgccagca aacagcacga cgatttcctc 4741 gtcgatcagg acctggcaac gggacgtttt cttgccacgg tccaggacgc ggaagcggtg 4801 cagcagcgac accgattcca ggtgcccaac gcggtcggac gtgaagccca tcgccgtcgc 4861 ctgtaggcgc gacaggcatt cctcggcctt cgtgtaatac cggccattga tcgaccagcc 4921 caggtcctgg caaagctcgt agaacgtgaa ggtgatcggc tcgccgatag gggtgcgctt 4981 cgcgtactcc aacacctgct gccacaccag ttcgtcatcg tcggcccgca gctcgacgcc 5041 ggtgtaggtg atcttcacgt ccttgttgac gtggaaaatg accttgtttt gcagcgcctc 5101 gcgcgggatt ttcttgttgc gcgtggtgaa cagggcagag cgggccgtgt cgtttggcat 5161 cgctcgcatc gtgtccggcc acggcgcaat atcgaacaag gaaagctgca tttccttgat 5221 ctgctgcttc gtgtgtttca gcaacgcggc ctgcttggcc tcgctgacct gttttgccag 5281 gtcctcgccg gcggtttttc gcttcttggt cgtcatagtt cctcgcgtgt cgatggtcat 5341 cgacttcgcc aaacctgccg cctcctgttc aagacgacgc gaacgctcca cggcggccga 5401 tggcgcgggc agggcagggg gagccagttg cacgctgtcg cgctcgatct tggccgtagc 5461 ttgctggacc atcgagccga cggactggaa ggtttcgcgg ggcgcacgca tgacggtgcg 5521 gcttgcgatg gtttcggcat cctcggcgga aaaccccgcg tcgatcagtt cttgcctgta 5581 tgccttccgg tcaaacgtcc gattcattca ccctccttgc gggattgccc cgactcacgc 5641 cggggcaatg tgcccttatt cctgatttga cccgcctggt gccttggtgt ccagataatc 5701 caccttatcg gcaatgaagt cggtcccgta gaccgtctgg ccgtccttct cgtacttggt 5761 attccgaatc ttgccctgca cgaataccag cgaccccttg cccaaatact tgccgtgggc 5821 ctcggcctga gagccaaaac acttgatgcg gaagaagtcg gtgcgctcct gcttgtcgcc 5881 ggcatcgttg cgccacatct aggatctgcc aggaaccgta aaaaggccgc gttgctggcg 5941 tttttccata ggctccgccc ccctgacgag catcacaaaa atcgacgctc aagtcagagg 6001 tggcgaaacc cgacaggact ataaagatac caggcgtttc cccctggaag ctccctcgtg 6061 cgctctcctg ttccgaccct gccgcttacc ggatacctgt ccgcctttct cccttcggga 6121 agcgtggcgc tttctcatag ctcacgctgt aggtatctca gttcggtgta ggtcgttcgc 6181 tccaagctgg gctgtgtgca cgaacccccc gttcagcccg accgctgcgc cttatccggt 6241 aactatcgtc ttgagtccaa cccggtaaga cacgacttat cgccactggc agcagccact 6301 ggtaacagga ttagcagagc gaggtatgta ggcggtgcta cagagttctt gaagtggtgg 6361 cctaactacg gctacactag aaggacagta tttggtatct gcgctctgct gaagccagtt 6421 accttcggaa aaagagttgg tagctcttga tccggcaaac aaaccaccgc tggtagcggt 6481 ggtttttttg tttgcaagca gcagattacg cgcagaaaaa aaggatctca agaagatcct 6541 ttgatctttt ctacggggtc tgacgctcag tggaacgaaa actcacgtta agggattttg 6601 gtcatgagat tatcaaaaag gatcttcacc tagatccttt taaattaaaa atgaagtttt 6661 aaatcaatct aaagtatata tgagtaaact tggtctgaca gttaccaatg cttaatcagt 6721 gaggcaccta tctcagcgat ctgtctattt cgttcatcca tagttgcctg actccccgtc 6781 gtgtagataa ctacgatacg ggagggctta ccatctggcc ccagtgctgc aatgataccg 6841 cgagaaccac gctcaccggc tccagattta tcagcaataa accagccagc cggaagggcc 6901 gagcgcagaa gtggtcctgc aactttatcc gcctccatcc agtctattaa ttgttgccgg 6961 gaagctagag taagtagttc gccagttaat agtttgcgca acgttgttgc cattgctaca 7021 ggcatcgtgg tgtcacgctc gtcgtttggt atggcttcat tcagctccgg ttcccaacga 7081 tcaaggcgag ttacatgatc ccccatgttg tgcaaaaaag cggttagctc cttcggtcct 7141 ccgatcgttg tcagaagtaa gttggccgca gtgttatcac tcatggttat ggcagcactg 7201 cataattctc ttactgtcat gccatccgta agatgctttt ctgtgactgg tgagtactca 7261 accaagtcat tctgagaata gtgtatgcgg cgaccgagtt gctcttgccc ggcgtcaata 7321 cgggataata ccgcgccaca tagcagaact ttaaaagtgc tcatcattgg aaaacgttct 7381 tcggggcgaa aactctcaag gatcttaccg ctgttgagat ccagttcgat gtaacccact 7441 cgtgcaccca actgatcttc agcatctttt actttcacca gcgtttctgg gtgagcaaaa 7501 acaggaaggc aaaatgccgc aaaaaaggga ataagggcga cacggaaatg ttgaatactc 7561 atactcttcc tttttcaata ttattgaagc atttatcagg gttattgtct catgagcgga 7621 tacatatttg aatgtattta gaaaaataaa caaatagggg ttccgcgcac gaattggcca 7681 gcgctgccat ttttggggtg aggccgttcg cggccgaggg gcgcagcccc tggggggatg 7741 ggaggcccgc gttagcgggc cgggagggtt cgagaagggg gggcaccccc cttcggcgtg 7801 cgcggtcacg cgcacagggc gcagccctgg ttaaaaacaa ggtttataaa tattggttta 7861 aaagcaggtt aaaagacagg ttagcggtgg ccgaaaaacg ggcggaaacc cttgcaaatg 7921 ctggattttc tgcctgtgga cagcccctca aatgtcaata ggtgcgcccc tcatctgtca 7981 gcactctgcc cctcaagtgt caaggatcgc gcccctcatc tgtcagtagt cgcgcccctc 8041 aagtgtcaat accgcagggc acttatcccc aggcttgtcc acatcatctg tgggaaactc 8101 gcgtaaaatc aggcgttttc gccgatttgc gaggctggcc agctccacgt cgccggccga 8161 aatcgagcct gcccctcatc tgtcaacgcc gcgccgggtg agtcggcccc tcaagtgtca 8221 acgtccgccc ctcatctgtc agtgagggcc aagttttccg cgaggtatcc acaacgccgg 8281 cggccgcggt gtctcgcaca cggcttcgac ggcgtttctg gcgcgtttgc agggccatag 8341 acggccgcca gcccagcggc gagggcaacc agcccggtga gcgtcgcaaa ggagatcctg 8401 atctgactga tgggctgcct gtatcgagtg gtgattttgt gccgagctgc cggtcgggga 8461 gctgttggct ggctggtggc aggatatatt gtggtgtaaa caaattgacg cttagacaac 8521 ttaataacac attgcggacg tttttaatgt actggggtgg atgcagtggg ccccac SN772 GT1:transferrin protein expression product (SEQ ID NO: 23) MASINRPIVFFTVCLFLLCDGSLAGGDPERTVRWCTISTHEANKCASFRENVLRILESGPFVSCVKKTSH MDCIKAISNNEADAVTLDGGLVYEAGLKPNNLKPVVAEFHGTKDNPQTHYYAVAVVKKDTDFKLNELRGK KSCHTGLGRSAGWNIPMAKLYKELPDPQESIQRAAANFFSASCVPCADQSSFPKLCQLCAGKGTDKCACS NHEPYFGYSGAFKCLMEGAGDVAFVKHSTVFDNLPNPEDRKNYELLCGDNTRKSVDDYQECYLAMVPSHA VVARTVGGKEDVIWELLNHAQEHFGKDKPDNFQLFQSPHGKDLLFKDSADGFLKIPSKMDFELYLGYEYV TALQNLRESKPPDSSKDECMVKWCAIGHQERTKCDRWSGFSGGAIECETAENTEECIAKIMKGEADAMSL DGGYLYIAGKCGLVPVLAENYKTEGESCKNTPEKGYLAVAVVKTSDANINWNNLKDKKSCHTAVDRTAGW NIPMGLLYSKINNCKFDEFFSAGCAPGSPRNSSLCALCIGSEKGTGKECVPNSNERYYGYTGAFRCLVEK GDVAFVKDQTVIQNTDGNNNEAWAKNLKKENFEVLCKDGTRKPVTDAENCHLARGPNHAVVSRKDKATCV EKILNKQQDDFGKSVTDCTSNFCLFQSNSKDLLFRDDTKCLASIAKKTYDSYLGDDYVRAMTNLRQCSTS KLLEACTFHKPGGWSHPQFEKGGGSGGGSGGSAWSHPQFEK GT1 targeting peptide in single underline Golden gate cloning GG linker residues in italics Bovine Transferrin in bold, note first Methionine residue coding for the start codon is removed Twin-Strep-tag in double underline Example 3 This Example was designed to determine levels of purity of transferrin in plant extracts that may be suitable for use in cell culture (e.g., demonstrate functionality with little or no toxicity in cultured cells). Benth leaf extract B9 media was used as the base media. In the B9 media, 20 μg / mL of commercially sourced transferrin protein and decreasing amounts of benth leaf extract (2000, 1000, 500, 250, 100 and 50 μg / mL of B9 media in order from left to right) that were either not cleaned up (left panel of Figure 7) or cleaned up (right panel of Figure 7) prior to use were added. The “clean up” procedure included dialysis by way of a 10 kDa MWCO membrane and subsequent filtration by way of a 10 or 30 kDa MWCO membrane. The retentate fraction from the filtration step was then re- solubilised. A positive control (i.e., B9 media with 20 μg / mL transferrin and no benth extract) and a negative control (B9 media only) are also included in Figure 7. As can be observed in Figure 7, the filtration procedure resulted in a significant reduction in toxicity of the benth leaf extract. Moreover, significantly improved cell viability (about or > 70% cell viability compared to the B9 media positive control) was observed with the 50 μg / mL benth extract and 20 μg / mL transferrin mixture (i.e., a purity level of 40% transferrin by weight of the benth leaf extract, which equated to a purity level of 73% transferrin per total protein content of the benth leaf extract). Improved cell viability over the unfiltered control was also observed with the 100 μg / mL benth extract and 20 μg / mL transferrin mixture (i.e., a purity level of 20% transferrin by weight of the benth leaf extract, which equated to a purity level of 57% transferrin per total protein content of the benth leaf extract). Camelina seed extract Similar experiments as per the benth leaf extract were then performed in relation to Camelina seed extracts (i.e., 2000, 1000, 500, 250, 100 and 50 μg / mL of Camelina seed extract (in order from left to right) that was either unfiltered (left panel of Figure 8) or filtered with a 10 kDa MWCO filter (right panel of Figure 8)). Again, the filtration procedure resulted in a significant reduction in toxicity of the Camelina seed extract (Figure 8). A significant improvement in cell viability (> 70% cell viability compared to the B9 media positive control) was observed with the 250 μg / mL Camelina seed extract and 20 μg / mL transferrin mixture (i.e., a purity level of 8% transferrin by weight of the Camelina seed extract, which equated to a purity level of 48% transferrin per total protein content of the Camelina seed extract), the 100 μg / mL Camelina seed extract and 20 μg / mL transferrin mixture (i.e., a purity level of 20% transferrin by weight of the Camelina seed extract, which equated to a purity level of 70% transferrin per total protein content of the Camelina seed extract) and the 50 μg / mL Camelina seed extract and 20 μg / mL transferrin mixture (i.e., a purity level of 40% transferrin by weight of the Camelina seed extract, which equated to a purity level of 82% transferrin per total protein content of the Camelina seed extract). Example 4 This prophetic Example provides a method that may be utilised to produce bovine transferrin in Camelina seeds. Materials & Methods The generation of transgenic Camelina plants that stably express transferrin in their seeds may be performed by modifying the method of generating such plants described in Lu and Kang, Plant Cell Rep (2008) 27:273–278, which is incorporated by reference herein in its entirety. In brief, a genetic construct including a bovine transferrin gene (e.g., SEQ ID NO: 3) driven by a seed-specific phaseolin promoter (see, e.g., Sengupta-Gopalan et al., 1985, Proc Natl Acad Sci U S A 82:3320–3324) can be constructed. The genetic construct may also include a selection marker, such as DsRed, driven by a constitutive promoter, such as the constitutive cassava vein mosaic virus promoter. The genetic construct can then be introduced into an Agrobacterium strain (such as strain GV3101 (pMP90)) by electroporation, such as per Lu and Kang supra. Growth of the transformed Agrobacterium can then be commenced 2–3 days prior to plant transformation, such as per Lu and Kang supra. Camelina plants may then be inoculated with a suspension of the transformed Agrobacterium, such as by placing pots with plants at the flowering stage inside a vacuum desiccator and immersing their inflorescences into the inoculum contained in a beaker. Vacuum can then be applied as required (e.g., held for 5 min at a pressure of 85 kPa). The treated Camelina plants can then be covered by plastic bags for 24 h before returning to normal growth in a greenhouse until maturity. Once mature, transgenic plants may then be screened for those having seeds expressing the selection marker, such as by PCR, microscopy or visual detection. The selected transgenic plants may then be screened for expression of bovine transferrin protein, such as by LC-MS, PCR or western blot. A low purity extract of the bovine transferrin from the seeds of those selected transgenic Camelina plants may then be obtained and functionally tested as per Example 1 above. Example 5 This Example examined further purification methods to improve the functionality of plant- expressed transferrin. SteptactinXT based purification of transferrin from benth plants expressing the SN772 construct as previously described (Example 2) was performed. After the final dialysis step as described in Example 1, the eluate was then passed over a PD10 buffer exchange column (Merk #GE17-0851-01) and reconstituted in Phosphate Buffered Saline (PBS) media. This step aimed to remove biotin from the buffer which could potentially hinder cell growth in downstream assays. C2C12 cells were then tested for cell growth using this further purified transferrin in a range of concentrations added to B9 media, from 40-200ug / ml. Cell numbers were assayed over 9 days. Compared to the control cells in B9 media which had no transferrin added, addition of plant purified transferrin led to a greater rate of cell growth (Figure 9). Increasing the concentration of transferrin correlated with greater volumes of cells. Compared to control cells with commercial transferrin spiked at a concentration of 40 μg / mL, the rate of growth of the cells was higher for plant-derived transferrin at 9 days, where the commercial transferrin cells rate of growth decreased on the 9thday of the assay. Together these results demonstrated that plant-derived transferrin further purified with a PD10 buffer exchange step enabled robust cell proliferation comparable with commercial transferrin.

Claims

CLAIMS:

1. A method of producing a component protein, said method including the steps of: (a) providing a plant configured to express the component protein that has been cultivated under suitable conditions to express the component protein, wherein the component protein is of non-human origin; and (b) extracting a low purity extract of the component protein from the plant.

2. A method of producing a component protein for a culture media, said method including the steps of: (a) providing a plant configured to express the component protein, wherein the component protein is of non-human origin; (b) cultivating the plant under conditions and for a time sufficient to express the component protein; and (c) extracting a low purity extract of the component protein from the plant.

3. The method of Claim 1 or Claim 2, wherein the component protein is present in an amount less than about 95% of a total protein content of the low purity extract.

4. The method of any one of the preceding claims, wherein the component protein is present in an amount of less than about 80% of a total protein content of the low purity extract.

5. The method of any one of the preceding claims, wherein the extraction step comprises a dialysis and / or filtration step.

6. The method of Claim 5, wherein the dialysis and / or filtration step includes dialysing and / or filtering the culture medium with a membrane having a molecular weight cut off of at least about 2.5 kDa.

7. The method of Claim 6, wherein the membrane has a molecular weight cut off of between about 5 kDa and about 15 kDa or between about 25 kDa and about 35 kDa.

8. The method of Claim 7, wherein the membrane has a molecular weight cut off of about 10 kDa, about 30 kDa or about 50 kDa.

9. The method of any one of the preceding claims, further include the step of lyophilising the low purity extract of the component protein.

10. The method of any one of the preceding claims, wherein the plant is or comprises a safflower plant, a soybean plant, a benth plant, a camelina plant or a canola plant.

11. The method of any one of the preceding claims, wherein the component protein is of an origin selected from the group consisting of a non-human mammalian species, an avian species and a teleost species, such as a bovine, a chicken or a salmon.

12. The method of any one of the preceding claims, wherein the component protein is selected from the group consisting of transferrin, albumin, insulin, insulin-like growth factor 1 (IGF-1), insulin-like growth factor 2 (IGF-2), fibroblast growth factor 2 (FGF2) activin, transforming growth factor β (TGF-β), neuregulin 1 (NRG1) and any combination thereof.

13. The method of any one of the preceding claims, wherein the component protein is transferrin.

14. An isolated component protein produced according to the method of any one of Claims 1 to 13.

15. A low purity extract of a component protein, wherein the component protein has been produced by a plant configured to express the component protein and wherein the component protein is of non-human origin.

16. A kit for producing a culture medium for culturing non-human animal cells, said kit comprising a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to the non-human animal cells.

17. The kit of Claim 16, further comprising a base medium.

18. A culture medium for culturing non-human animal cells comprising: (a) a base medium; and (b) a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to the non-human animal cells.

19. The culture medium of Claim 18, wherein the culture medium is free or substantially free of serum.

20. A method of producing a culture medium for culturing non-human animal cells, said method including the steps of: (a) providing a base medium; (b) adding a low purity extract of a component protein to the base medium, wherein the component protein has been produced by a plant and is of a same or similar species to the non- human animal cells.

21. A method of culturing non-human animal cells, said method including the step of culturing the non-human animal cells in a culture medium comprising a base medium and a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to that of the non-human animal cells.

22. A method of in vitro meat production, said method including the steps of: (a) providing a plurality of non-human animal cells; and (b) culturing the non-human animal cells in a culture medium comprising a base medium and a low purity extract of a component protein, wherein the component protein has been produced by a plant and is of a same or similar species to that of the non-human animal cells.

23. The method of Claim 21 or Claim 22, further including the earlier step of isolating the plurality of non-human cells from an animal source.

24. The method of any one of Claims 21 to 23, wherein the component protein is of an origin selected from the group consisting of bovine, porcine and teleost.

25. The method of any one of Claims 21 to 24, further including the step of harvesting a meat product produced from culturing the non-human animal cells.

26. The kit of Claim 16 or Claim 17, the culture medium of Claim 18 or Claim 19 or the method of any one of Claims 20 to 25, wherein the low purity extract of the component protein has been produced by the method of any one of Claims 1 to 13 or is that of Claim 14 or Claim 15.

27. The kit, the culture medium or the method of any one of Claims 16 to 26, wherein the component protein is present in the low purity extract in an amount less than about 95% of a total protein content of the low purity extract.

28. The kit, the culture medium or the method of any one of Claims 16 to 27, wherein the component protein is present in the low purity extract in an amount less than about 80% of a total protein content of the low purity extract.

29. A meat product produced according to the method of any one of Claims 21 to 28.

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