Application of Thn3 protein and Thn3 gene in increasing plant growth amount, nitrogen utilization rate, protein content and root length

Abstract

The invention relates to the technical field of biology, in particular to application of a Thn3 protein and a Thn3 gene in increasing the growth amount, the nitrogen utilization rate, the protein content and the root length of a plant. The invention excavates a multifunctional key gene Thn3 which can regulate and control the plant biomass and can also improve the nitrogen utilization rate, the protein content and the root length of the plant. According to the specific embodiment of the invention, deep analysis and identification are carried out on the function of the corn plant through a transgenic method, and the effect of the Thn3 gene on improving the biomass, the nitrogen utilization rate, the protein content and the root length of the corn plant is further defined. The biomass, the nitrogen utilization rate, the protein content and the root length of the transgenic maize plant with the over-expressed Thn3 gene are all remarkably improved. The method is of great significance to cultivation of high-biomass and high-protein corn.

Description

Technical Field

[0001] The present invention relates to the field of biotechnology, and in particular to the application of Thn3 protein and Thn3 gene in improving plant growth, nitrogen utilization rate, protein content and root length. Background Art

[0002] Since its introduction to Europe in the 16th century, corn has gradually spread across the globe, expanding its cultivation and becoming a major food crop. In China, corn cultivation and production are both among the highest in the world, and improvements in its yield and quality are crucial for ensuring food security. As one of the world's most productive crops, corn boasts rich nutrients, low cost, and easy storage and processing, making it widely used in livestock and poultry feed. Feed consumption is currently the largest consumer destination for corn.

[0003] Corn biomass, or the total biomass accumulated during its growth, is a key indicator of corn growth and yield potential. Increasing corn biomass is particularly important given the global population's growth and shrinking arable land. This not only increases grain production, meeting basic food needs and improving corn feed availability, but also reduces costs and dependence on imported soybeans, thereby improving the economic benefits of the livestock industry.

[0004] Nitrogen, an essential nutrient in corn growth and development, is closely linked to physiological processes such as photosynthesis, respiration, and metabolism. An adequate nitrogen supply promotes corn growth, increases leaf area and photosynthetic rate, thereby boosting biomass and yield. However, excessive nitrogen fertilizer use can lead to excessive vegetative growth, tender tissues, and reduced resistance to pests and diseases and adverse environmental conditions. It can also damage soil structure, reduce soil fertility, and cause soil compaction and infertility. Unabsorbed nitrogen fertilizer can also flow into water bodies with rainfall, causing eutrophication and triggering a series of environmental problems. Therefore, identifying key genes for efficient nitrogen utilization in corn and developing new high-protein varieties are important research directions for promoting the sustainable development of agriculture in my country. Summary of the Invention

[0005] The purpose of the present invention is to provide applications of Thn3 protein and Thn3 gene in improving plant growth, nitrogen utilization, protein content and root length, so as to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides the use of Thn3 protein in any of the following:

[0008] (1) Increase plant biomass;

[0009] (3) Improve plant nitrogen utilization efficiency;

[0010] (3) Increase the protein content of plant stems;

[0011] (4) Increase the length of plant roots;

[0012] (5) Cultivate plant varieties with high nitrogen utilization efficiency;

[0013] (6) Cultivate high-protein plant varieties;

[0014] (7) Cultivate plant varieties with well-developed root systems;

[0015] (8) Plant molecular breeding;

[0016] The amino acid sequence of the Thn3 protein is shown in SEQ ID NO.1.

[0017] Preferably, by upregulating the expression level of the Thn3 protein, plant biomass, plant nitrogen utilization efficiency, plant stem protein content and plant root length are increased.

[0018] Further preferably, the amino acid sequence of the Thn3 protein includes an amino acid sequence shown in SEQ ID NO.1, after one or more amino acid residues are substituted, deleted and / or added, to obtain an amino acid sequence that has more than 90% identity with the Thn3 protein and is related to plant high protein.

[0019] Further preferably, the amino acid sequence of the Thn3 protein includes the sequence shown in SEQ ID NO. 1 or the amino acid sequence of a fusion protein obtained by connecting a protein tag to the N-terminus or / C-terminus of a protein related to plant high protein that has more than 90% identity with the Thn3 protein.

[0020] The present invention provides the use of the gene encoding the Thn3 protein in any of the following:

[0021] (1) Increase plant biomass;

[0022] (3) Improve plant nitrogen utilization efficiency;

[0023] (3) Increase the protein content of plant stems;

[0024] (4) Increase the length of plant roots;

[0025] (5) Cultivate plant varieties with high nitrogen utilization efficiency;

[0026] (6) Cultivate high-protein plant varieties;

[0027] (7) Cultivate plant varieties with well-developed root systems;

[0028] (8) Plant molecular breeding;

[0029] The nucleotide sequence encoding gene Thn3 is shown in SEQ ID NO.2.

[0030] Preferably, by upregulating the expression level of the coding gene Thn3, plant biomass, plant nitrogen utilization efficiency, plant stem protein content and plant root length are increased.

[0031] The present invention provides the use of a biomaterial containing a gene encoding Thn3 in any of the following:

[0032] (1) Increase plant biomass;

[0033] (3) Improve plant nitrogen utilization efficiency;

[0034] (3) Increase the protein content of plant stems;

[0035] (4) Increase the length of plant roots;

[0036] (5) Cultivate plant varieties with high nitrogen utilization efficiency;

[0037] (6) Cultivate high-protein plant varieties;

[0038] (7) Cultivate plant varieties with well-developed root systems;

[0039] (8) Plant molecular breeding;

[0040] The nucleotide sequence encoding gene Thn3 is shown in SEQ ID NO.2.

[0041] Further preferably, the biological material includes an expression cassette, a recombinant expression vector, a recombinant host cell or a recombinant bacterium.

[0042] Preferably, the plant is corn.

[0043] Further preferably, the corn variety is corn B73, Zhengdan 958, Xianyu 335, Jingke 968, Denghai 605, Demeya 1, Demeya 3, Heyu 187, Suyu 29, Jingnongke 728, Zhongdan 808 or Zhengda 808, but is not limited to the aforementioned varieties.

[0044] The present invention provides a method for increasing plant biomass, comprising the step of increasing the expression level of a Thn3 encoding gene in a plant; the nucleotide sequence of the Thn3 encoding gene is shown in SEQ ID NO.2.

[0045] More preferably, the plant is corn.

[0046] Further preferably, the corn variety is corn B73, Zhengdan 958, Xianyu 335, Jingke 968, Denghai 605, Demeya 1, Demeya 3, Heyu 187, Suyu 29, Jingnongke 728, Zhongdan 808 or Zhengda 808, but is not limited to the aforementioned varieties.

[0047] Further preferably, the increasing the expression level of the gene encoding Thn3 in the plant is achieved by introducing a recombinant expression vector containing the gene encoding Thn3 into the recipient plant.

[0048] Existing plant expression vectors can be used to construct a recombinant expression vector containing the encoding gene. These include binary Agrobacterium vectors and vectors suitable for plant microprojectile bombardment. These plant expression vectors may also contain the 3′ untranslated region of the exogenous gene, i.e., a polyadenylation signal and any other DNA fragments involved in mRNA processing or gene expression. The polyadenylation signal can direct the addition of polyadenylic acid to the 3′ end of the mRNA precursor. For example, the 3′ untranslated region of Agrobacterium crown gall-inducing (Ti) plasmid genes (such as the nopaline synthase gene, Nos) and plant genes (such as the soybean storage protein gene) all have similar functions.

[0049] When constructing a recombinant expression vector using the aforementioned coding gene Thn3, any enhancing promoter or constitutive promoter (e.g., the cauliflower mosaic virus (CAMV) 35S promoter, the maize ubiquitin promoter), or a tissue-specific expression promoter (e.g., a seed-specific expression promoter) can be added before the transcription initiation nucleotide. These can be used alone or in combination with other plant promoters. Furthermore, when constructing a recombinant expression vector using the coding gene Thn3, enhancers can also be used, including translation enhancers or transcription enhancers. These enhancer regions can be the ATG start codon or the start codon of an adjacent region, but must be in the same reading frame as the coding sequence to ensure correct translation of the entire sequence. The sources of these enhancers are diverse and can be either natural or synthetic. The translation initiation region can be derived from the transcription initiation region or a structural gene.

[0050] In order to facilitate the identification and screening of transgenic plant cells or plants, the plant expression vector used can be processed, such as by adding genes that can be expressed in plants and encode enzymes or luminescent compounds that can produce color changes (GUS gene, luciferase gene, etc.), antibiotic resistance markers (gentamicin marker, kanamycin marker, etc.), or chemical resistance marker genes (such as herbicide resistance genes).

[0051] In the present invention, the recombinant expression vector can be specifically a recombinant expression vector obtained by replacing the fragment between the SpeⅠ and BamhⅠ restriction sites of the UBI-cFLAG vector (SEQ ID NO.3) with the DNA molecule shown in SEQ ID NO.2 (encoding gene Thn3).

[0052] As an additional solution, the present invention provides a method for increasing plant biomass, comprising the step of introducing a biological material carrying a gene encoding Thn3 into a recipient plant; the nucleotide sequence of the gene encoding Thn3 is shown in SEQ ID NO.2.

[0053] More preferably, the biomaterial carrying the Thn3 encoding gene is introduced into the recipient plant, specifically by:

[0054] Plant cells or tissues are transformed by using conventional biological methods such as Ti plasmids, Ri plasmids, plant virus vectors, direct DNA transformation, microinjection, electroporation, Agrobacterium-mediated, etc., and the transformed plant tissues are cultivated into plants.

[0055] Transformed cells, tissues or plants are understood to include not only the end product of the transformation process, but also their transgenic progeny.

[0056] The present invention provides a method for improving nitrogen utilization efficiency of plants, comprising the step of increasing the expression level of a Thn3 encoding gene in plants; the nucleotide sequence of the Thn3 encoding gene is shown in SEQ ID NO.2.

[0057] More preferably, the plant is corn.

[0058] Further preferably, the corn variety is corn B73, Zhengdan 958, Xianyu 335, Jingke 968, Denghai 605, Demeya 1, Demeya 3, Heyu 187, Suyu 29, Jingnongke 728, Zhongdan 808 or Zhengda 808, but is not limited to the aforementioned varieties.

[0059] As an additional solution, the present invention provides a method for improving nitrogen utilization efficiency of plants, comprising the step of introducing biological material carrying a gene encoding Thn3 into the plant; the nucleotide sequence of the gene encoding Thn3 is shown in SEQ ID NO.2.

[0060] The present invention provides a method for increasing the protein content of plant stems, comprising the step of increasing the expression level of a Thn3 encoding gene in the plant; the nucleotide sequence of the Thn3 encoding gene is shown in SEQ ID NO.2.

[0061] More preferably, the plant is corn.

[0062] Further preferably, the corn variety is corn B73, Zhengdan 958, Xianyu 335, Jingke 968, Denghai 605, Demeya 1, Demeya 3, Heyu 187, Suyu 29, Jingnongke 728, Zhongdan 808 or Zhengda 808, but is not limited to the aforementioned varieties.

[0063] As an additional solution, the present invention provides a method for increasing the protein content of plant stems, comprising the step of introducing a biological material carrying a gene encoding Thn3 into a recipient plant; the nucleotide sequence of the gene encoding Thn3 is shown in SEQ ID NO.2.

[0064] The present invention provides a method for increasing the length of plant roots, comprising the step of increasing the expression level of a Thn3 encoding gene in the plant; the nucleotide sequence of the Thn3 encoding gene is shown in SEQ ID NO.2.

[0065] More preferably, the plant is corn.

[0066] Further preferably, the corn variety is corn B73, Zhengdan 958, Xianyu 335, Jingke 968, Denghai 605, Demeya 1, Demeya 3, Heyu 187, Suyu 29, Jingnongke 728, Zhongdan 808 or Zhengda 808, but is not limited to the aforementioned varieties.

[0067] As an additional solution, the present invention provides a method for increasing the length of plant roots, comprising the step of introducing a biological material carrying a gene encoding Thn3 into a recipient plant; the nucleotide sequence of the gene encoding Thn3 is shown in SEQ ID NO.2.

[0068] As an additional solution, the present invention provides a method for cultivating plant varieties with well-developed root systems, comprising the step of increasing the expression level of the gene encoding Thn3 in the plant; the nucleotide sequence of the gene encoding Thn3 is shown in SEQ ID NO.2.

[0069] More preferably, the plant is corn.

[0070] Further preferably, the corn variety is corn B73, Zhengdan 958, Xianyu 335, Jingke 968, Denghai 605, Demeya 1, Demeya 3, Heyu 187, Suyu 29, Jingnongke 728, Zhongdan 808 or Zhengda 808, but is not limited to the aforementioned varieties.

[0071] The present invention discloses the following technical effects:

[0072] This invention has discovered a multifunctional key gene, Thn3, that regulates plant biomass and improves nitrogen utilization efficiency, protein content, and root length. Specific examples of this invention, using transgenic methods, have conducted in-depth analysis and identification of its function, further clarifying the role of the Thn3 gene in improving maize plant biomass, nitrogen utilization efficiency, protein content, and root length. The results showed that transgenic maize plants overexpressing the Thn3 gene exhibited significant increases in biomass, nitrogen utilization efficiency, protein content, and root length compared to wild-type plants. This invention has important implications for the cultivation of high-biomass and high-protein maize. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0074] Figure 1 The plant phenotypes of Thn3 protein overexpressing corn material (Thn3-OE) and control (CK); wherein, LN-CK is the phenotype of CK under low nitrogen conditions, LN-Thn3-OE is the phenotype of Thn3-OE under low nitrogen conditions, HN-CK is the phenotype of CK under high nitrogen conditions, and HN-Thn3-OE is the phenotype of Thn3-OE under high nitrogen conditions;

[0075] Figure 2 Statistical graph of fresh weight of underground part of Thn3 protein overexpressing maize material (Thn3-OE) and control (CK); LN refers to low nitrogen conditions and HN refers to high nitrogen conditions;

[0076] Figure 3 Statistical graph of fresh weight of aboveground parts of Thn3 protein overexpressing maize material (Thn3-OE) and control (CK); LN refers to low nitrogen conditions, and HN refers to high nitrogen conditions;

[0077] Figure 4 The total biomass statistics of the Thn3 protein overexpressing maize material (Thn3-OE) and the control (CK); LN refers to low nitrogen conditions and HN refers to high nitrogen conditions;

[0078] Figure 5 Statistical graph of stem protein content in Thn3 protein overexpressing corn material (Thn3-OE) and control (CK). DETAILED DESCRIPTION

[0079] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0080] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0081] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0082] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0083] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0084] Example 1 Obtaining Thn3 protein overexpression corn material

[0085] By screening over 800 maize transcription factor mutants using a nitrogen concentration gradient, a nitrogen-deficient mutant was identified. This mutant is a loss-of-function mutant of the transcription factor Thn3. This mutant exhibits reduced biomass, decreased plant height, and impaired root development, suggesting a functional link to plant vegetative growth. Therefore, the present invention constructed a maize material overexpressing the Thn3 protein.

[0086] Thn3蛋白的氨基酸序列如SEQ ID NO.1所示,具体为:MPRSGGGGNGGGISSSSRVM PNLPAGFRFHPTDEELMVHYLMRQAASMPCPVPIIAEVNIYQCNPWDLPAKALFGDKEWFFFSPRDRKYPNGARPNRAAGSGYWKATGTDKAILSSSTPTSHGGANIVVGVKKALVFYGGRPPKGTKTDWIMHEYRLSGAADDDCKGSTRRRVSSSSSSSMRLDDWVLCRIHKKSNDFQLSSSSEHEHEQEEPAAGGSATTVEELDALVVVDNSSSSDTTTTTITTNDNNSTETAATHHDPQTMMMLSKSCSLTDLLDSIDYAALSSQMLLLDAPHPHADDPPPHMVYYPPAASATHQQAIIANNTNSNDDYYDDDNLLPTAAATAVDAAAAAVLLSSSPADTNGVNKRKRVTAVDYYGAAEPPTFFHHHLDDGGNSFFSTTKKLKPPPPSDSRHGGHFGTATASSYRDSQQLVDSASSSGVFFHQYGYGYSSSNPFLNLNQQQQLLLNSHIGMQ。

[0087]

[0088] The steps for overexpressing Thn3 protein in corn materials are as follows:

[0089] 1. The fragment between the SpeⅠ and BamhⅠ restriction sites of the vector UBI-FLAG (the nucleotide sequence of the vector UBI-FLAG is obtained by connecting SEQ ID NO. 3, SEQ ID NO. 4, and SEQ ID NO. 5 from the 5' end to the 3' end) was replaced with the Thn3 gene (SEQ ID NO. 2) to obtain the overexpression vector UBI-Thn3-FLAG. The overexpression vector was verified by sequencing to have the correct nucleotide sequence.

[0090] SEQ ID NO.3:

[0091]

[0092] SEQ ID NO.4:

[0093]

[0094] SEQ ID NO.5:

[0095]

[0096] 2. The overexpression vector UBI-Thn3-FLAG prepared in step 1 was introduced into Agrobacterium EHA105 competent cells to obtain recombinant bacteria.

[0097] 3. Use the recombinant bacteria obtained in step 2 to transform the recipient corn B73 inbred line to obtain T0 generation plants

[0098] 4. Using a primer pair consisting of primers Thn3-F and FLAG-R, perform PCR identification on the T0 generation plants obtained in step 3. Select T0 generation plants that test positive for the gene and self-pollinate to obtain T1 generation plants. Positive plants will amplify a band, while negative plants will not.

[0099] Thn3-F: 5'-GCAGACACCAACGGTGTGAACA-3' (SEQ ID NO. 6);

[0100] FLAG-R: 5'-TGTCGTGATCCTTAGTCTCCATCATG-3' (SEQ ID NO. 7).

[0101] 5. Identify the T1 generation plants obtained in step 4 according to the method in step 4, select the T1 generation plants identified as positive for self-pollination to obtain T2 generation plants.

[0102] 6. Identify the T2 generation plants obtained in step 5 according to the method in step 4, select the T2 generation plants identified as positive for self-pollination to obtain T3 generation plants, and identify them according to the method in step 4 to screen out positive transgenic T3 generation plants, which are the Thn3 protein overexpressing corn materials.

[0103] Example 2 Phenotypic Investigation of Thn3 Protein Overexpression Corn Materials

[0104] 1. Method

[0105] In 2024, CK (corn B73 inbred line) and Thn3 protein overexpressing corn materials (positive transgenic T3 plants constructed in Example 1, Thn3-OE) were germinated in a greenhouse in Wenjiang District, Chengdu. The seedlings were treated with deionized water until one leaf and one heart were removed from the endosperm. The seedlings were treated with LN (low nitrogen, specific conditions: 0.04 mM nitrogen Hoagland nutrient solution) and HN (high nitrogen, specific conditions: 4 mM nitrogen Hoagland nutrient solution) conditions for 11 days, and the indicators were tested, including plant phenotypes and physiological indicators (total biomass and fresh weight of above-ground and underground parts).

[0106] Biomass determination: Dig up the entire plant, clean the roots, remove excess soil, and weigh the entire plant. Cut the stem at the base and weigh the fresh weight of the aboveground and underground parts separately.

[0107] Plant nitrogen content determination: Nitrogen content in Thn3 protein-overexpressing maize was determined using a Dumas Rapid Nitrogen Analyzer. Samples were dried to constant weight at 65°C and then ground into powder using a grinder (60 Hz, 60 s). 50-70 mg of the powder was wrapped in tin foil and used as the test sample. Total nitrogen was determined using a Dumas Rapid Nitrogen Analyzer from Elementar, Germany. Before each measurement, four standards (asparagine samples) were weighed as internal controls. After instrument commissioning, the weight of each sample was entered into the weight column of the Rapid N Ultra software (v1.1.25). The program settings were (O2 dosing time: 60 s; O2 dosing flow rate: 120 mL / min; O2 cutoff threshold: 15%; autozero delay: 30 s; and peak anticipation: 90 s). Packaged samples were placed into the corresponding sample jars according to their serial number. Up to 55 samples could be tested in each round. Data were exported to Excel for analysis.

[0108] 2. Results

[0109] (1) Plant phenotype and physiological index test results

[0110] The phenotypes of Thn3 protein overexpressing maize material (Thn3-OE) and control (CK) are shown in Figure 1 The results of the aboveground fresh weight, underground fresh weight and total aboveground and underground fresh weight are shown in Figure 2-Figure 4 The results showed that compared with CK, the root length of Thn3-OE plants under LN and HN conditions was significantly increased. The total fresh weight (total biomass) of Thn3-OE plants under LN conditions increased by 31.9%, the underground part increased by 26.7%, and the aboveground part increased by 37.0%. While the total fresh weight (total biomass) of Thn3-OE plants under HN conditions increased by 15.7%, the underground part increased by 10.6%, and the aboveground part increased by 19.5%.

[0111] (2) Plant protein content test results

[0112] The results of the stalk protein content detection of Thn3 protein overexpressing corn material (Thn3-OE) and control (CK) are shown in Figure 5 The stem protein content of the control plants was 2.03%, while that of the Thn3 protein overexpressing corn material was 5.30%, which was 2.6 times higher.

[0113] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. Use of Thn3 protein in any of the following: (1) Increase plant biomass; (3) Improve plant nitrogen utilization efficiency; (3) Increase the protein content of plant stems; (4) Increase the length of plant roots; (5) Cultivate plant varieties with high nitrogen utilization efficiency; (6) Cultivate high-protein plant varieties; (7) Cultivate plant varieties with well-developed root systems; (8) Plant molecular breeding; The amino acid sequence of the Thn3 protein is shown in SEQ ID NO.

1.

2. The use according to claim 1, characterized in that By increasing the expression level of the Thn3 protein, plant biomass, plant nitrogen utilization efficiency, plant stem protein content and plant root length are increased.

3. Use of the gene encoding the Thn3 protein according to claim 1 in any of the following: (1) Increase plant biomass; (3) Improve plant nitrogen utilization efficiency; (3) Increase the protein content of plant stems; (4) Increase the length of plant roots; (5) Cultivate plant varieties with high nitrogen utilization efficiency; (6) Cultivate high-protein plant varieties; (7) Cultivate plant varieties with well-developed root systems; (8) Plant molecular breeding; The nucleotide sequence encoding gene Thn3 is shown in SEQ ID NO.

2.

4. The use according to claim 3, characterized in that By increasing the expression level of the coding gene Thn3, plant biomass, plant nitrogen utilization rate, plant stem protein content and plant root length are increased.

5. Use of biological materials containing the gene encoding Thn3 in any of the following: (1) Increase plant biomass; (3) Improve plant nitrogen utilization efficiency; (3) Increase the protein content of plant stems; (4) Increase the length of plant roots; (5) Cultivate plant varieties with high nitrogen utilization efficiency; (6) Cultivate high-protein plant varieties; (7) Cultivate plant varieties with well-developed root systems; (8) Plant molecular breeding; The nucleotide sequence encoding gene Thn3 is shown in SEQ ID NO.

2.

6. The use according to claim 1, 3 or 5, characterized in that The plant is corn.

7. A method for increasing plant biomass, characterized in that: The method comprises the steps of increasing the expression level of the coding gene Thn3 in the plant; the nucleotide sequence of the coding gene Thn3 is shown in SEQ ID NO.

2.

8. A method for improving nitrogen utilization efficiency of plants, characterized in that: The method comprises the steps of increasing the expression level of the coding gene Thn3 in the plant; the nucleotide sequence of the coding gene Thn3 is shown in SEQ ID NO.

2.

9. A method for increasing the protein content of plant stems, characterized in that: The method comprises the steps of increasing the expression level of the coding gene Thn3 in the plant; the nucleotide sequence of the coding gene Thn3 is shown in SEQ ID NO.

2.

10. A method for increasing the length of plant roots, characterized in that: The method comprises the steps of increasing the expression level of the coding gene Thn3 in the plant; the nucleotide sequence of the coding gene Thn3 is shown in SEQ ID NO.2.

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