BjuVAL1 gene of brassica juncea and application of BjuVAL1 gene in delaying bolting and flowering and stress resistance

Abstract

The invention discloses a brassica juncea BjuVAL1 gene and application thereof in delaying bolting and flowering and stress resistance, and relates to the technical field of plant biology. The mustard BjuVAL1 gene is obtained through a homologous cloning method, wild mustard is subjected to genetic transformation through an overexpression vector and an RNA interference vector of the BjuVAL1 gene through an agrobacterium-mediated method, and results show that compared with the wild mustard, an overexpression plant has an obvious late flowering phenotype, and an interference plant has an obvious early flowering phenotype. Therefore, the brassica juncea BjuVAL1 expression can delay bolting and flowering. A high-temperature treatment result of a transgenic line shows that a BjuVAL1 interference plant shows higher heat resistance than a non-transgenic plant, and an overexpression plant is opposite. The brassica juncea BjuVAL1 transgenic germplasm created by the invention has the characteristics of delaying bolting and flowering and resisting heat, and has great utilization value for increasing the yield of brassica juncea.

Description

Technical Field

[0001] The present invention relates to the field of plant biotechnology, and specifically relates to the application of BjuVAL1 transgenic mustard in regulating bolting and flowering of mustard and heat tolerance. Background Art

[0002] Mustard (Brassica juncea) belongs to the genus Brassica of the Brassicaceae family and is an important vegetable widely cultivated in the Yangtze River basin of China. Mustard can be divided into multiple different types according to its edible parts, including stem-use, leaf-use, root-use, and shoot-use, etc. Stem-use mustard includes stem-tuber mustard (pickled mustard tuber), bamboo shoot mustard, and baby mustard, etc., and they mainly use the swollen stem as the edible organ. The phenomenon of premature bolting and flowering leads to poor development of its product organs, seriously affecting the yield and quality. High temperature will prompt mustard to enter the reproductive period in advance, causing it to bolt prematurely and reducing the yield and quality of mustard. Pickled mustard tuber is a characteristic vegetable in China. Continuously increasing the yield of pickled mustard tuber is an important way to increase farmers' income. Therefore, in-depth exploration of the regulation mechanism of mustard bolting and flowering and its extreme temperature response mechanism is not only beneficial to the high-quality and high-yield production of mustard and the cultivation of new varieties with bolting resistance, but also of great significance to the sustainable and healthy development of the mustard industry.

[0003] The present invention aims to provide a method that can affect the bolting and flowering time of mustard and respond to extreme temperature stress. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides the BjuVAL1 gene of mustard and its application in delaying bolting and flowering and stress resistance. In this invention, the homologous cloning method is adopted to clone the BjuVAL1 gene in mustard. Through the Agrobacterium-mediated method to infect the hypocotyls of mustard, the overexpression vector and RNA interference vector of the BjuVAL1 gene are genetically transformed into mustard, which can inhibit / promote the bolting and flowering time of mustard, and the mustard genetically transformed with the RNA interference vector has good heat tolerance.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] The present invention provides the BjuVAL1 gene of mustard, and the nucleotide sequence of the BjuVAL1 gene is shown in SEQ ID NO.1.

[0007] The CDS sequence of the BjuVAL1 gene is 2352bp.

[0008] The present invention provides the protein encoded by the above BjuVAL1 gene, and the amino acid sequence of the protein is shown in SEQ ID NO.2.

[0009] The protein encoded by the BjuVAL1 gene contains 784 amino acids, including a B3-DNA domain, a zf-CW domain, and an EAR motif at the C-terminus.

[0010] The present invention provides a recombinant expression vector of the above-mentioned BjuVAL1 gene, a host cell or an engineered bacterium containing the recombinant expression vector.

[0011] The present invention provides the use of the above-mentioned BjuVAL1 gene in promoting / delaying the bolting and flowering of mustard and improving / inhibiting the heat tolerance of mustard.

[0012] Preferably, the method for delaying the bolting and flowering of mustard / inhibiting the heat tolerance of mustard is: ligating the BjuVAL1 gene to an expression vector, transforming it into mustard via Agrobacterium-mediated transformation, and overexpressing the BjuVAL1 gene in transgenic mustard.

[0013] Preferably, the method for promoting the bolting and flowering of mustard / improving the heat tolerance of mustard is: ligating the BjuVAL1 gene to an interference vector, transforming it into mustard via Agrobacterium-mediated transformation, and reducing the expression level of the BjuVAL1 gene in transgenic mustard.

[0014] Preferably, the transformation into mustard via Agrobacterium-mediated transformation is specifically introducing it into the cells, tissues or organs of mustard.

[0015] The present invention provides a method for delaying plant flowering or inhibiting plant heat tolerance, by introducing the above-mentioned BjuVAL1 gene, the protein encoded by the above-mentioned BjuVAL1 gene, or the above-mentioned recombinant expression vector, host cell or engineered bacterium into the mustard genome and overexpressing it in transgenic mustard.

[0016] The present invention provides a method for promoting plant flowering or improving plant heat tolerance, by introducing the above-mentioned BjuVAL1 gene, the protein encoded by the above-mentioned BjuVAL1 gene, or the above-mentioned recombinant expression vector, host cell or engineered bacterium into the mustard genome and inhibiting its expression in transgenic mustard.

[0017] Compared with the prior art, the beneficial effects of this solution are:

[0018] The present invention uses homologous cloning to clone the BjuVAL1 gene in mustard, and proves that BjuVAL1 functions as a transcription factor through subcellular localization experiments. And by infecting the hypocotyls of mustard via Agrobacterium-mediated transformation, the overexpression vector and RNA interference vector of the BjuVAL1 gene are genetically transformed into mustard. The flowering time of the obtained plants is inhibited and promoted respectively, and the RNA interference line of mustard has good heat tolerance. The transgenic germplasm of mustard BjuVAL1 created by the present invention has the characteristics of delaying bolting and flowering and heat tolerance, and has great utilization value for the yield increase of mustard. Description of the Drawings

[0019] Figure 1 Analysis of the amino acid sequences of the proteins encoded by the VAL1 homologous genes of different species in Brassicaceae in Example 1 (Figure A is the phylogenetic tree analysis, Figure B is the domain analysis, and Figure C is the positional relationship and structural differences of the B3 domain of the VAL1 gene in different species);

[0020] Figure 2 Results diagram of subcellular localization in Example 2 (GFP is green fluorescent protein; RFP is red fluorescent protein; Bright field is the bright field, showing cell viability; Merge is a double staining technique; A is the control empty vector, and B is the localization of BjuVAL1 in mustard in the nucleus);

[0021] Figure 3 Shown is the tissue culture process of transgenic mustard in Example 3 (the left figure is the tissue culture process of the overexpressing mustard plant, and the right figure is the tissue culture process of the RNA interference mustard plant; A is callus induction, B is root induction, and C is transplantation);

[0022] Figure 4 Phenotype identification of transgenic mustard in Example 4 (A is the phenotype of the overexpressing mustard plant; B is the qPCR detection of the expression fold of the overexpressing mustard; C is the statistical analysis of the flowering time of the overexpressing mustard plant; D is the phenotype of the RNA interference mustard plant; E is the qPCR detection of the expression fold of the RNA interference mustard; F is the statistical analysis of the flowering time of the RNA interference mustard plant; WT is the control, BjuVAL1#OE-1 and BjuVAL#OE-2 are the overexpressing lines of mustard; BjuVAL1#Ri-1 and BjuVAL1#Ri-2 are the RNAi interference lines of mustard; * is P<0.05; ** is P<0.01, and **** is P<0.0001).

[0023] Figure 5 Phenotype of transgenic mustard plants under the condition of 42 °C high temperature in Example 5 (WT is wild-type mustard; OE-1 is overexpressing line 1; OE-2 is overexpressing line 2; Ri-1 is RNA interference line 1; Ri-2 is RNA interference line 2).

[0024] Figure 6Analysis of POD, SOD, CAT enzyme activities and MDA content of transgenic mustard plants under 42 °C high temperature conditions in Example 6 (A is the analysis of the change in POD enzyme activity of mustard before and after treatment, B is the analysis of the change in SOD enzyme activity of mustard before and after treatment, C is the analysis of the change in CAT enzyme activity of mustard before and after treatment, D is the analysis of the change in MDA content of mustard before and after treatment; WT is the control, BjuVAL1#OE is the overexpression line of mustard, BjuVAL1#Ri is the RNAi interference line; Control is under normal temperature, Heattolerance is under high temperature conditions, * is P<0.05; ** is P<0.01, **** is P<0.0001). Detailed implementation manners

[0025] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0026] Unless otherwise specified, the materials, reagents, etc. used in the following examples can all be obtained from commercial channels.

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] Example 1 Cloning of the cDNA sequence of the mustard BjuVAL1 gene

[0029] 1. Extraction of total RNA from mustard seedling leaves

[0030] According to the operation guide of the Eastep Super Total RNA Extraction Kit provided by Shanghai Promega Corporation, total RNA was extracted from different tissues of mustard.

[0031] 2. First-strand cDNA synthesis

[0032] (1) Removal of gDNA: Add 2 μL of gDNA Clean Reaction Mix Ver.2, 1 μg of RNA sample, and supplement with RNase-free water to 10 μL. The mixture is reacted at 42 °C for 2 min and held at 4 °C.

[0033] (2) Reverse transcription reaction: 10 μL of the reaction solution from step (1), 4 μL of 5×Evo M-MLV RT Reaction MixVer.2, 6 μL of RNase-free water. The mixture is reacted at 37 °C for 15 min, 85 °C for 5 s, and held at 4 °C.

[0034] 3. Cloning of the mustard BjuVAL1 gene

[0035] Design primers using Oligo 7 software: forward primer F: 5’-ATGTTCCAAGTCAAAACGGGG-3’, reverse primer R: 5’-TCAGCTTGAACCTTTCGACTCT-3’. Using the first-strand cDNA after reverse transcription as a template, amplify the BjuVAL1 gene by PCR with the above forward and reverse primer combination. The PCR amplification system (50 μL) is: 25 μL of Primer Star enzyme, 2 μL each of the forward and reverse primers, 2 μL of template cDNA, ddH 2 O 19 μL. The PCR amplification program is: 98°C for 2 min; 98°C for 30 s, 58°C for 30 s, 72°C for 2 min 30 s, 34 cycles; 72°C for 10 min.

[0036] After the PCR reaction, detect by 1.5% (w / v) agarose gel electrophoresis, cut out the target band, and use a gel extraction / DNA purification kit (DC301) to recover the above target band. The specific steps refer to the kit instruction manual. Ligate the gel extraction product with the cloning vector

[0037] The coding region sequence of the mustard BjuVAL1 gene cDNA was translated to obtain the BjuVAL1 amino acid sequence as follows: MFQVKTGSKMCMNASCGSISTAEWKKGWPL RSGALADLCFRCGSAYESSLFCETFHLDQSGWRECYLCNKRLHCGCIASKLVVEFMDYGGVGCSTCTNCHQPNLNNRGESSGLFSRLPMNRQHTNGESGMNVDGVRSLADFFSQPLVQGDDKREEFMPHRGFNNLMKPDNATTGYMQDSADMQESSSPSQPSLNMALASLPYSLSFANATKKLMDAASQSHPVQCSASSILQKPSKSALGTPPGTSKSAQARIGRPPVEGRGKSHLLPRYWPKYTDKELQQISGNLNLKIVPLFEKTLSASDAGRIGRLVLPKACAEAYFPPISQSEGIPLKIQDVKGKEWTFQFRFWPNNNSRMYVLEGVTPCIQSMMLQ AGDTVTFSRVDPGGKLIMGFRKAAHTGDIQGRGLTNGTSNEDTSSSGVTETPTSKNASSCPSQTPGELKSLPEHLSLKKGEVNGGRSCDDPSRVKDKKRTRTVGAKSKRLLWHSEESMEVRLKWEETQELIRPCPSDKPTIVVIEEHEFEEFDEPPVFGKRTILTSRPSGEQERWASCDDCFKWRRLPVDALLPAKWTCSDNVWDESRCSCSAPEESLKELENVPRIGKEYKKRRTGVSQTGKTEQELSGLDALASAAALGDTLGEEEAEATTTTRHPRHRVGCSCIVCIQPPSGKGRHKASCVCTVCSTVKRRFKTLMMRRKKKQLEREEIEAAAAANQENKEDGKTGRIDLNSDPYNRGEVEAVGVEEKDESKRRVAGECLGVAQVGDVIGVTELEGEAEKIGEESKGSS*, Further, the amino acid sequence was subjected to a homologous sequence alignment analysis with the genomes of Arabidopsis thaliana, Chinese cabbage, Brassica oleracea, Brassica nigra, Brassica napus, mustard, and Brassica carinata in the Brassicaceae family that have been published. The results showed that BjuVAL1 clustered together with BniB003956 of Brassica nigra, had the same domain, and had the highest sequence similarity, proving that the cloning of the mustard BjuVAL1 gene was successful.Moreover, the encoded protein of the mustard BjuVAL1 gene contains one B3-DNA domain, one zf-CW domain, and one EAR motif (see Figure 1 ).

[0038] Example 2 Subcellular Localization

[0039] (1) Inoculate the preserved Agrobacterium liquid onto an LB solid medium containing 50 μg / mL kanamycin and 20 μg / mL rifampicin, streak it, and culture it at 28 °C for 2 days;

[0040] (2) Pick a correct single colony from the medium, inoculate it into 4 mL of LB liquid medium containing kanamycin and rifampicin, and culture it on a shaker at 28 °C and 220 rpm for 24 hours to obtain the live liquid;

[0041] (3) Take 2 mL of the live liquid and add it to 50 mL of LB liquid medium containing the same resistance drugs respectively, amplify it on a shaker at 28 °C and 220 rpm, and culture it until the OD 600 value reaches 0.8 - 1.0;

[0042] (4) Transfer the amplified bacterial liquid to a 50 mL centrifuge tube, centrifuge it at 4000 rpm for 10 minutes, and remove the supernatant;

[0043] (5) Wash the bacterial cells with a resuspension solution containing 10 mM MgCl 2 , 10 mM MES-KOH (pH = 5.6), and 150 μM AS, adjust the bacterial liquid to OD 600 to 0.8 - 1.0, and let it stand for 1 hour in the dark;

[0044] (6) After mixing the bacterial liquid, use a 1 mL syringe to infect the back of the tobacco;

[0045] (7) After culturing in the dark for 24 hours, transfer the tobacco to normal light conditions and culture it for another 24 hours. Then, use the 35S::ZmH2B-mCherry fusion plasmid as the nuclear marker at the same time. After 48 hours of tobacco infection, take the injection site to make slides and perform fluorescence observation and photography under a laser confocal microscope.

[0046] The results show that mustard BjuVAL1 is localized in the nucleus, indicating that the mustard BjuVAL1 gene can function as a transcription factor (see Figure 2 ).

[0047] Example 3 Culturing Mustard BjuVAL1 Overexpression and RNA Interference Plants

[0048] The tissue culture process of mustard BjuVAL1 overexpression and RNA interference plants includes the following steps (see Figure 3):

[0049] (1) Sowing and pre-culturing: Select 20 mustard seeds with plump grains and place them in a 200 mL sterile tissue culture flask. Soak them in 75% ethanol for 45 seconds and then rinse with sterile deionized water for 60 seconds; soak them in 10% NaClO solution for 15 minutes, with continuous gentle shaking during this period to ensure sufficient contact; rinse with sterile deionized water for 60 seconds and repeat 5 times to thoroughly remove the residual disinfectant. Evenly sow the disinfected seeds on the surface of MS solid medium and culture them in an incubator for 7 days; after the seeds germinate, cut the hypocotyls of the seedlings into explant segments about 1 cm long. Transfer the explants to the pre-culture medium (MS solid medium + 3 mg / L 6-BA + 0.2 mg / L NAA) and culture for 2 days.

[0050] (2) Activation and dark culture: Dip a small amount of Agrobacterium tumefaciens liquid containing the recombinant plasmid with an inoculation loop, streak it on YEB solid medium containing 25 μg / mL Rif and 60 μg / mL Kan, and culture it in a constant temperature incubator at 28°C for 2 days. Screen positive clones by colony PCR, pick positive colonies and inoculate them into 4 mL YEB liquid medium (containing 25 mg / L Rif and 60 mg / L Kan), and culture them on a shaker at 28°C until the OD 600 value is 0.5 - 0.6. Transfer 50 mL of the bacterial liquid to a 50 mL sterile centrifuge tube, centrifuge at 4°C and 4000 rpm for 10 minutes, discard the supernatant; resuspend the cells with 25 mL of pre-cooled MS liquid medium to obtain the Agrobacterium infection solution. Immerse the pre-cultured hypocotyls in the infection solution and gently shake for 10 minutes to ensure sufficient contact between the bacterial liquid and the tissue. After the infection, blot the residual bacterial liquid on the surface of the hypocotyls with sterile filter paper. Place the infected hypocotyls flat on the surface of the pre-culture medium (MS solid medium + 3 mg / L 6-BA + 0.2 mg / L NAA) and culture them under dark conditions for 2 days.

[0051] (3) Differentiation and rooting culture: After the dark culture, transfer the co-cultured hypocotyls to the MS screening medium (MS solid medium + 3 mg / L 6-BA + 0.2 mg / L NAA + 25 mg / L Hyg + 400 mg / L Cb), and culture them at 25 °C under the photoperiod of 16 hours of light / 8 hours of darkness. Replace the screening medium every 7 days until adventitious buds differentiate from the hypocotyls. Conduct multiple subcultures on the surviving adventitious buds, and then cut healthy adventitious buds and insert them into the rooting medium (MS solid medium + 0.2 mg / L NAA + 25 mg / L Hyg + 400 mg / L Cb) to induce root development. After the adventitious bud roots grow to 3 - 5 cm, open the tissue culture bottle for acclimatization for 2 - 3 days to adapt to the external environment. After removing the medium attached to the roots, transplant the seedlings into the sterilized substrate to obtain the overexpression and RNA interference transgenic lines of BjuVAL1 gene in Brassica juncea var. tumida Tsen et Lee.

[0052] Example 4 Phenotypic Identification of Transgenic Mustard Plants and Statistics of Flowering Time

[0053] Select the leaves of T1 plants of the overexpression and interference transgenic lines of BjuVAL1 in Brassica juncea var. tumida Tsen et Lee respectively, extract RNA and reverse transcribe it into cDNA, and then perform quantitative PCR to detect the expression of the target gene.

[0054] The results show that: compared with the non-transgenic control WT, in the overexpression lines BjuVAL1#OE-1 and BjuVAL1#OE-2, the expression levels of the BjuVAL1 gene increased by about 4.4 and 5 times respectively ( Figure 4 B). On the contrary, in the RNAi interference lines BjuVAL1#Ri-1 and BjuVAL1#Ri-2, the expression levels of the target gene decreased, about 0.4 and 0.45 of the control respectively ( Figure 4 E). This indicates that: the expression levels of the BjuVAL1 gene in both the overexpression and interference lines changed significantly, which laid a foundation for the subsequent study of the function of this gene. At the same time, plant the above transgenic lines and the control under long-day conditions and observe the plant phenotypes (see Figure 4 A and Figure 4 D). The results show that: the average bolting and flowering time of the overexpression plants of BjuVAL1 in Brassica juncea var. tumida Tsen et Lee (BjuVAL#OE) was extended to 35 days, showing an obvious phenotype of delayed flowering ( Figure 4 C); however, the average bolting and flowering time of the RNAi interference plants of BjuVAL1 in Brassica juncea var. tumida Tsen et Lee (BjuVAL#Ri) was 26 days, showing a phenotype of early flowering ( Figure 4 F). This indicates that the BjuVAL1 gene in Brassica juncea var. tumida Tsen et Lee is a bolting and flowering inhibitor.

[0055] Example 5 Phenotypic Identification of Transgenic Mustard under High Temperature Conditions

[0056] Transgenic BjuVAL1 overexpressing mustard lines, RNA interference mustard lines, and non-transgenic control plants were selected and subjected to a high temperature treatment at 42°C. The experimental results showed that there were no significant differences in the growth of all mustard plants before the treatment. However, after 48 hours of high temperature treatment, obvious wilting occurred in the leaves of both the overexpressing mustard lines and the control plants, while no obvious changes were observed in the interference lines. Among them, compared with the control, the BjuVAL1 overexpressing mustard lines were close to death. Compared with the control, there was no obvious wilting in the leaves of the BjuVAL1 interference lines (see Figure 5 ). This indicates that the overexpressing mustard plants do not have the ability to tolerate high temperatures, while the interference plants have good heat tolerance, suggesting that mustard BjuVAL1 is sensitive to high temperatures.

[0057] Example 6 Determination of Physiological Indexes of Transgenic Mustard under High Temperature Conditions

[0058] A MDA kit from Suzhou Mengxi Biopharmaceutical Co., Ltd. (including 1 bottle of 60 mL extraction solution, 1 bottle of reagent one powder, and 2 bottles of reagent two powder) was used to measure the physiological indexes of transgenic mustard plants under high temperature conditions.

[0059] Add 45 mL of distilled water to reagent one, and add 20 mL of reagent one to each bottle of reagent two. Weigh about 0.1 g of leaf tissue, add 1 mL of extraction solution, and perform ice bath homogenization. Centrifuge at 1000 rpm at 4°C for 10 min, take the supernatant, and place it on ice for later measurement. Take 225 μL of the supernatant and 675 μL of reagent two, mix well in a centrifuge tube, heat in a water bath at 92°C for 30 min (cover tightly to prevent water loss), cool, centrifuge at 12000 rpm at 25°C for 10 min. Take 0.8 mL of the supernatant and place it in a 1 mL glass cuvette, measure the absorbance at 532 nm and 600 nm respectively, and record it as A 532 and A 600 , calculate ΔA = A 532 -A 600 . The MDA content (nmol / g) = 25.58×(ΔA + 0.0076) / W. W is the sample mass.

[0060] The enzyme activities of POD, SOD, and CAT in BjuVAL1 overexpressing mustard plants were all significantly reduced, about 2.5, 3.5, and 2.2 times lower than those of the control group respectively. However, the enzyme activities of POD, SOD, and CAT in BjuVAL1 interference mustard plants were all significantly increased, about 4.6, 4.4, and 5.4 times higher than those of the control group respectively. The MDA content in overexpressing transgenic plants was higher than that of non-transgenic controls, about 1.3 times higher. The MDA content in interference mustard plants was significantly lower than that of the control, about 1.5 times lower. In summary, the interference plants have obvious heat tolerance (see Figure 6 ).

[0061] The above specific embodiments are only explanations of the present invention, and they are not limitations of the present invention. After reading this specification, those skilled in the art can make modifications to these embodiments that do not contribute creatively as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. Brassica juncea BjuVAL1 gene, characterized in that The nucleotide sequence of the BjuVAL1 gene is shown in SEQ ID NO.

1.

2. The protein encoded by the BjuVAL1 gene according to claim 1, characterized in that The amino acid sequence of the protein is shown in SEQ ID NO.

2.

3. A recombinant expression vector containing the BjuVAL1 gene according to claim 1, and a host cell or engineered bacteria containing the recombinant expression vector.

4. Use of the BjuVAL1 gene according to claim 1 in promoting / delaying bolting and flowering of Brassica juncea and improving / inhibiting heat tolerance of Brassica juncea.

5. The use according to claim 4, characterized in that: The method for delaying the bolting and flowering of mustard / inhibiting the heat resistance of mustard is: connecting the BjuVAL1 gene to an expression vector, transforming it into mustard through Agrobacterium-mediated transformation, and making the BjuVAL1 gene over-expressed in the transgenic mustard.

6. The use according to claim 4, characterized in that: The method for promoting bolting and flowering of mustard / improving heat resistance of mustard is: connecting the BjuVAL1 gene to an interference vector, transforming it into mustard through Agrobacterium-mediated transformation, and making the BjuVAL1 gene expressed silently in the transgenic mustard.

7. The use according to claim 5 or 6, characterized in that: The transformation into Brassica juncea mediated by Agrobacterium specifically refers to introduction into cells, tissues or organs of Brassica juncea.

8. A method for delaying plant flowering or inhibiting plant heat resistance, characterized in that: The BjuVAL1 gene according to claim 1, the BjuVAL1 gene protein according to claim 2 or the recombinant expression vector, host cell or engineered bacteria according to claim 3 are introduced into the mustard genome and overexpressed in the transgenic mustard.

9. A method for promoting plant flowering or improving plant heat resistance, characterized in that: The BjuVAL1 gene according to claim 1, the BjuVAL1 gene protein according to claim 2 or the recombinant expression vector, host cell or engineered bacteria according to claim 3 are introduced into the mustard genome, and are silently expressed in the transgenic mustard.

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