Expression vector containing dexamethasone induction system and application of expression vector in tomato fruit development

Abstract

The invention relates to the technical field of plant genetic engineering, in particular to an expression vector containing a dexamethasone induction system and application of the expression vector in tomato fruit development. The expression vector provided by the invention comprises a glucocorticoid receptor induction system and a target gene loaded into the glucocorticoid receptor induction system, wherein the target gene comprises at least one of an SlNAM2 gene and an SlNAM3 gene. The expression vector can be used for constructing a transgenic tomato plant, and gene expression in tomato fruits can be accurately regulated and controlled through induction, so that the quality of the tomato fruits can be well improved. The process has small influence on the growth of the whole tomato plant, can realize specific accurate regulation and control on the tomato fruit, and is beneficial to industrialization of tomato fruit quality regulation and control.

Description

Technical Field

[0001] The present application belongs to the technical field of plant genetic engineering, and in particular relates to an expression vector containing a dexamethasone induction system and its application in tomato fruit development. Background Art

[0002] Tomato (Solanum lycopersicum) is one of the most important economic crops in the world. As the most widely planted and highest-yielding fruit vegetable in the world, tomato is not only a food source, but also an important industrial raw material, widely used in the production of ketchup, tomato juice and other processed foods. In addition, tomato has become one of the model crops in plant science research because of its relatively small genome and easy manipulation. The tomato genome has been fully sequenced, and the rich mutant resources provide a powerful tool for studying fruit development, ripening and quality control.

[0003] In the field of plant gene regulation research, the glucocorticoid receptor induction system (abbreviated as GR system) has been widely used in model plants such as rice (Oryza sativa) and Arabidopsis thaliana as a plant chemical induction expression system with high induction efficiency and wide application range. This system combines the induction effect of dexamethasone (DEX) with the GR vector to achieve precise regulation of the target gene entering the cell nucleus. At present, the research on the GR system is mainly focused on the leaves and roots of plants, and has not yet been deeply explored in the fruit of tomato (Solanum lycopersicum). Summary of the invention

[0004] The purpose of the present application is to provide an expression vector containing a dexamethasone induction system and its application in tomato fruit development, aiming to solve the technical problem of how to improve the quality of tomato fruit.

[0005] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0006] In a first aspect, the present application provides an expression vector comprising a glucocorticoid receptor induction system and a target gene loaded into the glucocorticoid receptor induction system, wherein the target gene comprises at least one of a SlNAM2 gene and a SlNAM3 gene.

[0007] In some embodiments, the nucleotide sequence of the S1NAM2 gene is shown in SEQ ID No. 1;

[0008] And / or, the nucleotide sequence of the SlNAM3 gene is shown in SEQ ID No.2.

[0009] In some embodiments, the glucocorticoid receptor inducible system comprises a plp-35S-Flag vector and an inserted glucocorticoid receptor nucleotide sequence, and the nucleotide sequence of the glucocorticoid receptor inducible system is shown as SEQ ID No.3.

[0010] In a second aspect, the present application provides an application, namely, the application of the expression vector provided in the first aspect of the present application in tomato fruit development.

[0011] In a third aspect, the present application provides a kit for tomato breeding, comprising the expression vector provided in the first aspect of the present application.

[0012] In some embodiments, the kit further comprises dexamethasone.

[0013] In a fourth aspect, the present application provides a tomato breeding method, comprising:

[0014] Constructing the expression vector provided in the first aspect of the present application;

[0015] The expression vector is transferred into a tomato recipient for cultivation to obtain a transgenic tomato plant;

[0016] After the transgenic tomato plants grow tomato fruits, dexamethasone is injected into the tomato fruit stalks for induction cultivation.

[0017] In some embodiments, the period when the transgenic tomato plant grows tomato fruits is the color breaking period;

[0018] And / or, the induction cultivation includes: growing the tomato fruit in the dark for 2 to 3 days, and then growing it in the light for 10 to 11 days.

[0019] In some embodiments, the injection concentration of dexamethasone into the tomato stalk is 1-30 μM.

[0020] In some embodiments, the injection concentration of dexamethasone into the tomato stalk is 5 μM.

[0021] The present application designs an expression vector including a glucocorticoid receptor induction system and a target gene (i.e., at least one of the SlNAM2 gene and the SlNAM3 gene), and can construct a transgenic tomato plant using the expression vector, thereby precisely regulating gene expression in tomato fruits by induction, thereby greatly improving the quality of tomato fruits. This process has little effect on the growth of the entire tomato plant, and can achieve specific and precise regulation of tomato fruits, providing a more accurate tool for studying gene functions in fruits, with good specificity and reliability. Therefore, the expression vector, kit, and related tomato breeding methods and applications provided by the present application are conducive to the industrialization of tomato fruit quality regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 It is a process roadmap for constructing and verifying an expression vector containing a dexamethasone inducible system provided in the examples of the present application;

[0024] Figure 2 1 is a diagram of transgenic tomato plants cultivated using expression vectors in the examples of the present application; wherein A is a plp-35S:SlNAM2-GR plant phenotype, B is a wild type plant phenotype, and C is a plp-35S:SlNAM3-GR plant phenotype;

[0025] Figure 3 This is an electrophoresis diagram for identifying transgenic tomato plants cultivated using expression vectors in the examples of the present application; wherein lanes 1 to 16 are wild-type plants, lanes 17 to 56 are plp-35S:SlNAM2-GR plants, and lanes 57 to 96 are plp-35S:SlNAM3-GR plants;

[0026] Figure 4 is a tomato fruit phenotype diagram after 13 days of cultivation by expression vector transfer and dexamethasone injection induction in the examples of the present application; wherein E is the tomato fruit phenotype of the plp-35S:SlNAM2-GR plant, and F is the tomato fruit phenotype of the plp-35S:SlNAM3-GR plant;

[0027] Figure 5 This is a graph of the average expression levels of the four genes SlZDS, SlPSY1, SlXTH3, and SlGLK1 in tomato fruits of tomato plants cultivated by expression vector transfer and dexamethasone injection induction in the examples of the present application. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0030] In the present application, "at least one" means one or more, "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items.

[0031] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0032] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0033] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0034] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0035] Existing research based on the GR system mainly focuses on the leaves and roots of plants, and has not yet been deeply explored in fruits, which makes the feasibility of the GR system in regulating fruits uncertain. Especially in tomato (Solanum lycopersicum) fruits, research on the GR system is still blank. In addition, existing technical means are mostly focused on large-scale tissues or the entire plant, lacking research on the fine regulation of fruits.

[0036] The quality of tomato fruit directly affects its market value. Consumers usually evaluate its quality based on the color, firmness, flavor and nutritional value of the fruit. The color of the fruit is mainly determined by the carotenoid content, while the firmness of the fruit is closely related to the modification of its cell wall. The ripening process of tomato fruit can be divided into four main periods: green ripening period, color breaking period, color change period and red ripening period. Among these periods, the color breaking period is the key period of fruit ripening, when the fruit begins to change from green to red. At this time, the large-scale synthesis of carotenoids and the modification of the cell wall have a decisive influence on the final quality of the fruit.

[0037] Therefore, the present application example applies the GR system in tomato fruit development for the first time, and improves the quality of tomato fruit by inducing the expression of the target gene. Specifically, the present application example fuses the glucocorticoid receptor (GR) with the SlNAM2 gene or the SlNAM3 gene, and a large amount of SlNAM2 / SlNAM3 transcription factor protein generated by overexpression exists outside the cell nucleus, and cannot enter the cell nucleus to play the role of transcription factor without the glucocorticoid dexamethasone (DEX) treatment. When the DEX solution is injected into the tomato for treatment, the GR loses the inhibitory effect on the entry of SlNAM2 / SlNAM3 protein into the nucleus after combining with DEX, so that the SlNAM2 / SlNAM3 transcription factor generated by overexpression enters the nucleus in large quantities to play a role. The present application example not only reveals the mechanism of action of the GR system in fruit development, but also determines various important conditions for tomato breeding through experimental data to achieve a more efficient and economical gene expression regulation scheme, laying the foundation for the widespread application of the GR system in agricultural production in the future. The specific technical scheme is introduced below.

[0038] In a first aspect, the present application provides an expression vector. The expression vector of the present application can induce the expression of a target gene in tomato fruit, the expression vector comprising a glucocorticoid receptor induction system and a target gene loaded into the glucocorticoid receptor induction system, the target gene comprising at least one of a SlNAM2 gene and a SlNAM3 gene.

[0039] Exemplarily, the target gene may be the S1NAM2 gene, or the target gene may be the S1NAM3 gene, or the target gene may be both the S1NAM2 gene and the S1NAM3 gene.

[0040] The present application embodiment designs an expression vector including a glucocorticoid receptor induction system and the above-mentioned target gene, and can construct a transgenic tomato plant with the expression vector, and can precisely regulate gene expression in tomato fruit by induction, thereby greatly improving the quality of tomato fruit. This process has little impact on the growth of the entire tomato plant, and can achieve specific and precise regulation of tomato fruit, providing a more accurate tool for studying gene functions in fruit, with good specificity and reliability, and is conducive to the industrialization of tomato fruit quality regulation.

[0041] In some embodiments, the nucleotide sequence of the SlNAM2 gene is shown as SEQ ID No.1; the mRNA nucleotide sequence of the SlNAM3 gene is shown as SEQ ID No.2.

[0042] >Solyc03g115850.2.1NAC domain protein IPR003441(AHRD V1***-B9I557_POPTR); contains Interpro domain(s)IPR003441No apical meristem(NAM)protein:

[0043] SEQ ID No.1:

[0044]

[0045] >Solyc06g069710.2.1NAC domain protein IPR003441(AHRD V1***-B9I557_POPTR);contains Interpro domain(s)IPR003441No apical meristem(NAM)protein

[0046] SEQ ID No.2:

[0047]

[0048] In some embodiments, the glucocorticoid receptor inducible system comprises a plp-35S-Flag vector and an inserted glucocorticoid receptor nucleotide sequence, and the nucleotide sequence of the glucocorticoid receptor inducible system is shown as SEQ ID No.3.

[0049] SEQ ID No.3:

[0050]

[0051] In the second aspect, the present application provides an application, that is, the application of the expression vector provided in the first aspect of the present application in the development of tomato fruit.

[0052] Fruit quality is a key factor affecting crop yield and consumer willingness, and its gene regulation mechanism is complex and unique. This application example uses the above expression vector in the process of tomato fruit development to explore the feasibility of using the expression vector system in the process of tomato fruit development and its regulatory effect on specific gene expression. The results show that tomato fruit quality can be accurately regulated.

[0053] In a third aspect, the present application provides a kit for tomato breeding. The kit of the present embodiment includes the expression vector provided in the first aspect of the present embodiment.

[0054] In some embodiments, the kit further comprises dexamethasone.

[0055] In a fourth aspect, the present application provides a tomato breeding method. The tomato breeding method of the present application comprises the following steps:

[0056] S01: constructing the expression vector provided in the first aspect of the embodiment of the present application;

[0057] S02: transferring the expression vector into a tomato recipient for cultivation to obtain a transgenic tomato plant;

[0058] S03: When the transgenic tomato plants grow tomato fruits, dexamethasone is injected into the tomato fruit stalks for induced cultivation.

[0059] The embodiment of the present application successfully applies the above-mentioned expression vector system to the quality control of tomato fruit through the fruit stalk injection method, which can directly and solely affect the gene expression in the tomato fruit, reduce the impact on the plant as a whole, and more accurately control the quality of the tomato fruit. Specifically, after the transgenic tomato plant with the above-mentioned specific expression vector grows tomato fruit, the embodiment of the present application injects dexamethasone into the tomato fruit through the fruit stalk for induced cultivation; the results show that this can not only regulate gene expression, but also improve the key qualities of the tomato fruit such as color, hardness and nutritional content. This can also expand the actual application scenarios in the field of plant gene regulation, especially for the research and industrial application of fruit development and quality control, which has important reference value.

[0060] By injecting dexamethasone on the fruit stalk, exogenous substances can be precisely introduced into the tomato fruit, allowing the treated substances to act accurately and efficiently on the treated area, allowing the tomato plant to regulate local physiological and biochemical reactions while maintaining the normal development process of the plant.

[0061] In some embodiments, the period when the transgenic tomato plant grows tomato fruits is the color breaking period. By injecting dexamethasone into the tomato fruit during the color breaking period, the expression levels of specific genes related to tomato fruit quality (such as SlZDS, SlPSY1, SlXTH3, SlGLK1) were verified, and the results showed that the expression levels could be significantly increased.

[0062] The examples of this application focus on genes related to carotenoid synthesis and cell wall modification. SlZDS and SlPSY1, these two genes are involved in the biosynthesis of carotenoids, affecting the color and nutritional components of the fruit; overexpression of SlGLK1 can improve the photosynthesis efficiency of the fruit and increase the content of sugar and carotenoids; SlXTH3 is involved in the modification of the cell wall during fruit ripening, affecting the texture and hardness of the fruit. Overexpression of these genes can improve the quality of tomato fruit.

[0063] In some embodiments, the induction cultivation includes: growing the tomato fruit in the dark for 2 to 3 days, and then growing it in the light for 10 to 11 days. The induction cultivation process can better improve the quality of the tomato fruit. Specifically, after injecting dexamethasone, an opaque black bag can be covered on the treated tomato fruit to ensure that the tomato fruit is protected from light. After bagging for 2 to 3 days, the black bag is removed, and the fruit growth is continued to be observed for 10 to 11 days to obtain high-quality tomato fruit.

[0064] In some embodiments, 13 days after the injection of dexamethasone into the fruit stalk, the tomato fruit was harvested, photographed, and the overexpression of the target gene was verified. RNA was extracted by the CTAB method, and the cDNA obtained by reverse transcription was subjected to quantitative real-time PCR using the TransStart Tip Green qPCR SuperMix kit. -ΔΔCt The expression level of the target gene was calculated using SlACTIN as the internal reference.

[0065] In some embodiments, the injection concentration of dexamethasone into the tomato stalk is 1-30 μM.

[0066] Specifically, in the embodiment of the present application, 39.236g of DEX powder was weighed and dissolved with 10mL of anhydrous ethanol to obtain a 10M stock solution. The stock solution was diluted to prepare solutions with different DEX concentrations for different control groups, as shown in Table 1. Prepare the control group solution: dissolve 100μL of anhydrous ethanol in 100mL of ultrapure water to obtain a 0.1% ethanol solution. Setting up the experimental group in this way can reveal the effects of different concentrations of DEX treatment on the expression of the target gene. The embodiment of the present application designed a concentration gradient of multiple DEX treatments, and the results showed that the injection of dexamethasone at a concentration of 1 to 30μM can improve the comprehensive quality of tomato fruit to a certain extent after a period of induced cultivation.

[0067] In some embodiments, the injection concentration of dexamethasone into the tomato stalk is 5 μM. This experiment explored in detail the effect of DEX concentration on the regulation of tomato fruit quality by setting up dexamethasone (DEX) treatment groups with different concentration gradients. The experimental results showed that in the 5 μM DEX treatment group, the four key genes related to fruit quality (SlZDS, SlPSY1, SlXTH3, SlGLK1) all showed the highest peak expression levels. In addition, from an economic point of view, the 5 μM DEX treatment concentration also has the best cost-effectiveness, which can not only improve production efficiency, but also reduce production costs, providing a scientific basis for improving tomato fruit quality.

[0068] Furthermore, the present application example contains the expression vector construction and verification process route of the dexamethasone inducible system, such as Figure 1 As shown, it includes: (1) construction of transgenic vector: recombination and connection of SlNAM2 / SlNAM3 target gene and GR linear vector to construct expression vector and transformation; (2) plant tissue culture; (3) construction and identification of transgenic plants; (4) induction by dexamethasone treatment; (5) detection of target gene expression. The present application embodiment achieves the regulation of specific genes in tomato fruit by constructing specific transgenic plants, preparing dexamethasone (DEX) solution, injecting fruit stalks, and subsequent gene expression analysis.

[0069] The following describes the invention in conjunction with specific embodiments.

[0070] Example 1

[0071] 1 Construction of transgenic plants

[0072] 1.1 Homologous recombination primers were designed based on the cDNA sequences of tomato target genes SlNAM2 and SlNAM3 as shown in Table 1. The mRNA of wild-type tomato fruit was extracted using the Trizol method, and the cDNA of wild-type tomato fruit was obtained using a reverse transcription kit. The cDNA was amplified using homologous recombination primers with KOD high-fidelity enzyme as a template, and the target gene fragment was separated by 1.5% agarose gel electrophoresis. The target fragment was recovered according to the Quick Gel Extraction Kit instructions. At the same time, the plp-35S-GR plasmid was digested with restriction endonucleases XhoⅠ and BamHI from NEB, and the linear plp-35S-GR fragment after digestion was recovered. The linear plp-35S-GR fragment was connected to the SlNAM2 / SlNAM3 sequence using a plasmid recombination kit (the method refers to the Basic Seamless Cloning and Assembly Kit instructions) to obtain plp-35S:SlNAM2-GR and plp-35S:SlNAM3-GR recombinant plasmids. The recombinant plasmid was transformed into DH5ɑ Escherichia coli competent cells by heat shock method, and the correctly connected plp-35S:SlNAM2-GR and plp-35S:SlNAM3-GR plasmids were obtained by resistance screening and sequencing, and then transformed into GV3101 Agrobacterium competent cells by heat shock method. The plp-35S:SlNAM2-GR and plp-35S:SlNAM3-GR transgenic plants were obtained by tissue culture method (plant phenotypes are as follows Figure 2 shown).

[0073] Table 1 Homologous recombination primers for each gene

[0074]

[0075] 1.2 Conduct homozygous identification on the next generation of plants. Pick red ripe tomato fruits, squeeze and break them to collect seeds; soak the seeds in 0.5% sulfuric acid solution for 15 minutes, then rinse with water to remove attached pulp tissue; dry the washed seeds and store them dry. Soak the seeds in ultrapure water and shake at 28°C and 220rpm to germinate; sow the germinated seeds on moist nutrient soil and plant them in soil. Take about 100 mg of young stems and leaves from each tomato plant, and use the CTAB method to extract the genome of the transgenic plant. The primers designed to verify the GR primers are shown in Table 2. Using the genome of the transgenic plant as a template, use TaqPlus Master Mix for PCR, and use electrophoresis to detect the reaction products. Screen out plp-35S:SlNAM2-GR and plp-35S:SlNAM3-GR transgenic positive plants (such as Figure 3As shown: Because the next generation of transgenic plants may have separated traits, this step screens homozygous positive transgenic plants from the lanes for subsequent experiments).

[0076] Table 2GR validation primers

[0077]

[0078] 2. Solution Preparation

[0079] 2.1 Preparation of dexamethasone (DEX) solution: Weigh 39.236 g of DEX powder and dissolve it in 10 mL of anhydrous ethanol to obtain a 10 M stock solution.

[0080] 2.2 The above stock solution was diluted with water to prepare solutions with different DEX concentrations, as shown in Table 3. Prepare the control solution: dissolve 100 μL of anhydrous ethanol in 100 mL of ultrapure water to obtain a 0.1% ethanol solution.

[0081] Table 3

[0082]

[0083] 2.3 All solutions are packaged, labeled and stored in a 4℃ refrigerator away from light.

[0084] 3. Fruit stalk injection treatment

[0085] 3.1 After the transgenic tomato fruit enters the color breaking stage, use a 1mL sterile syringe to draw 1mL of DEX solution of corresponding concentration or control solution. Select the fruit that is about to mature, select the part near the base of the fruit on the fruit stalk, use the syringe needle to make a small wound, and inject the DEX solution through the wound. The angle and position of the wound for each fruit should be consistent.

[0086] 3.2 Set up a wild-type control group to exclude the effect of mechanical damage on fruit gene expression, and mark all the treated fruits.

[0087] 4. Bagging

[0088] 4.1 After DEX solution injection, immediately cover the treated fruit with an opaque black bag to protect the fruit from light. Remove the black bag 3 days after bagging and continue to observe the growth status of the tomato fruit.

[0089] 5RNA extraction and analysis

[0090] 5.1 Thirteen days after the DEX solution injection treatment, the treated tomato fruits were collected and photographed (e.g. Figure 4The seeds were removed from the fruit and stored in a -80°C refrigerator. RNA was extracted using the CTAB method, and the cDNA obtained by inversion was subjected to quantitative real-time PCR using the TransStart Tip Green qPCR SuperMix Kit. -ΔΔCt The expression level of the target gene was calculated using SlACTIN as the internal reference.

[0091] The results are as follows Figure 5 As shown in the figure: In the 5μM DEX solution treatment group, the target genes (SlZDS, SlPSY1, SlXTH3 and SlGLK1) all showed the most significant overexpression. Compared with other treatment concentrations, the treatment of 5μM DEX solution not only has a more significant advantage in gene expression, but also is the most cost-effective choice from an economic perspective.

[0092] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An expression vector, characterized in that: The method comprises a glucocorticoid receptor induction system and a target gene loaded into the glucocorticoid receptor induction system, wherein the target gene comprises at least one of a SlNAM2 gene and a SlNAM3 gene.

2. The expression vector according to claim 1, characterized in that The nucleotide sequence of the S1NAM2 gene is shown in SEQ ID No. 1; And / or, the nucleotide sequence of the SlNAM3 gene is shown in SEQ ID No.

2.

3. The expression vector according to claim 1 or 2, characterized in that The glucocorticoid receptor induction system comprises a plp-35S-Flag vector and an inserted glucocorticoid receptor nucleotide sequence. The nucleotide sequence of the glucocorticoid receptor induction system is shown in SEQ ID No.

3.

4. Use of the expression vector according to any one of claims 1 to 3 in tomato fruit development.

5. A kit for tomato breeding, characterized in that: The invention comprises the expression vector according to any one of claims 1 to 3.

6. The kit according to claim 5, characterized in that The kit also includes dexamethasone.

7. A tomato breeding method, characterized in that: include: Constructing the expression vector according to any one of claims 1 to 3; The expression vector is transferred into a tomato recipient for cultivation to obtain a transgenic tomato plant; After the transgenic tomato plants grow tomato fruits, dexamethasone is injected into the tomato fruit stalks for induction cultivation.

8. The tomato breeding method according to claim 7, characterized in that: The period when the transgenic tomato plant grows tomato fruits is the color breaking period; And / or, the induction cultivation includes: growing the tomato fruit in the dark for 2 to 3 days, and then growing it in the light for 10 to 11 days.

9. The tomato breeding method according to claim 7, characterized in that: The injection concentration of dexamethasone injected into the tomato stalk is 1-30 μM.

10. The tomato breeding method according to any one of claims 7 to 9, characterized in that: The injection concentration of dexamethasone injected into the tomato stalk is 5 μM.

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