阅读说明：本技术 一种烟草新烟碱合成调控基因NtERF91的克隆和应用 (Cloning and application of tobacco neonicotinoid synthesis regulatory gene NtERF91 ) 是由 隋学艺 高玉龙 王丙武 宋中邦 李文正 李梅云 赵璐 袁诚 张洪博 师君丽 李永 于 2019-10-22 设计创作，主要内容包括：本发明公开了烟草新烟碱合成调控基因NtERF91及其克隆方法与应用,烟碱合成调控基因NtERF91核苷酸序列如SEQ ID：No.1所示,编码的氨基酸序列如SEQ ID：No.2所示。本发明还公开了新烟碱合成调控基因NtERF91的克隆方法,具体步骤包括：A、确定NtERF91基因序列；B、提取烟草RNA,反转录得到第一链cDNA；C、根据NtERF91基因序列设计合成特异性引物,以cDNA作为模板,进行PCR扩增；D、回收和纯化PCR产物；E、构建了含NtERF91基因的过表达载体。将过表达载体通过农杆菌介导的转化在烟草中过表达,制备转基因植株。获得的转基因植株新烟碱含量是对照的4倍以上。说明烟草NtERF91基因在培育高新烟碱含量的烟草方面具有较大的应用前景。(The invention discloses a tobacco neonicotinoid synthesis regulating gene NtERF91, a cloning method and application thereof, wherein the nucleotide sequence of the nicotine synthesis regulating gene NtERF91 is shown as SEQ ID: no.1, the coded amino acid sequence is shown as SEQ ID: no. 2. The invention also discloses a cloning method of the neonicotinoid synthesis regulatory gene NtERF91, which comprises the following steps: A. determining the sequence of the NtERF91 gene; B. extracting tobacco RNA, and performing reverse transcription to obtain first-strand cDNA; C. designing and synthesizing a specific primer according to the NtERF91 gene sequence, and carrying out PCR amplification by taking cDNA as a template; D. recovering and purifying the PCR product; E. an overexpression vector containing the NtERF91 gene was constructed. And (3) carrying out overexpression on the overexpression vector in tobacco through agrobacterium-mediated transformation to prepare a transgenic plant. The obtained transgenic plant has the neonicotine content more than 4 times that of the control. The tobacco NtERF91 gene has a wide application prospect in culturing tobacco with high neonicotine content.)

1. A tobacco neonicotinoid synthesis regulating gene NtERF91 is characterized in that the nucleotide sequence of the tobacco neonicotinoid synthesis regulating gene NtERF91 is shown in a sequence table SEQ ID NO: 1 is shown.

2. The tobacco neonicotinoid synthesis-regulating gene NtERF91 of claim 1, wherein the amino acid sequence encoded by the tobacco neonicotinoid synthesis-regulating gene NtERF91 is as set forth in SEQ ID NO: 2, respectively.

3. A method of cloning the tobacco neonicotinoid synthesis regulatory gene NtERF91 according to claim 1, comprising the steps of:

A. determining the sequence of the NtERF91 gene;

obtaining an NtERF91 gene sequence according to the analysis of the transcription group of the root tissue of the tobacco treated by jasmonic acid, and designing a gene cloning primer by utilizing the sequence:

forward primer NtERF91-BamH I:

GGATCCATGTTAACTAGTGTCAATACCACGT；

reverse primer NtERF 91-XhoI:CTCGAGTCAATTTTCAGCCAATTTTCTCTTC；

B. extracting tobacco root tissue RNA, and performing reverse transcription to obtain first-strand cDNA;

C. designing and synthesizing a specific primer according to the NtERF91 gene sequence, carrying out PCR amplification by taking the first strand cDNA obtained by reverse transcription as a template, and recovering and purifying a PCR product;

D. the purified product is connected with a carrier and is connected with a TOPO carrier through a kit reaction, and a connection system and the process are as follows: 4 μ L of purified product, 1 μ L of salt solution, 1 μ L

4. The method for cloning a regulatory gene NtERF91 for synthesizing Nicotiana tabacum neonicotinoid according to claim 3, wherein the reaction system for PCR amplification in step C is a Phusion high fidelity amplification enzyme reaction system with a total volume of 50 μ L, and comprises: 200ng cDNA, 10. mu.L of 5 XPPhusion HF reaction buffer, 1. mu.L of 10mM dNTP, 2UHigh-Fidelity DNA Polymerase, 1. mu.L each of 10. mu.M forward and reverse primers, and water was added to 50. mu.L.

5. The method for cloning a tobacco neonicotinoid synthesis regulatory gene NtERF91 according to claim 3, wherein the reaction conditions for PCR amplification in step C are

6. An over-expression vector of the gene NtERF91 for regulating the content of neonicotinoid in tobacco lamina as claimed in claim 1 or 2, wherein the over-expression vector of the gene NtERF91 for regulating the content of nicotine in tobacco lamina is pK2GW7-NtERF 91.

7. Use of the tobacco neonicotinoid synthesis-modulating gene NtERF91 of claim 1, wherein the tobacco neonicotinoid synthesis-modulating gene NtERF91 is used to obtain transgenic plants with significantly increased neonicotinoid content.

8. Use of the tobacco neonicotinoid synthesis-regulating gene NtERF91 according to claim 7, characterized in that the method for obtaining the NtERF91 transgenic tobacco comprises the following steps:

A. construction of overexpression cloning vectors:

1. cloned NtERF91 ligation of TOPO vectors

(1) Taking cDNA of root tissues of a tobacco variety Coker176 as a template, and carrying out amplification by using a NtERF91 gene specific primer to obtain a gene fragment with the size of about 0.5 kb; purifying and recovering;

(2) the recovered NtERF91 gene fragment was subjected to TOPO cloning and ligated toTransforming Escherichia coli DH5 alpha competent cells after Blunt II-TOPO (3.5kb) vector, extracting plasmid for PCR detection, selecting plasmid with amplification product size of about 0.5kb to extract DNA, and the constructed vector is named as pTOPO-NtERF 91;

(3) because the upstream and downstream primers of the gene are respectively provided with recognition sites of BamH I and Xho I, the two enzymes are selected to carry out double enzyme digestion detection on a plasmid sample which is detected correctly, and a target gene fragment gel is recovered; performing BamH I and Xho I double enzyme digestion detection on pTOPO, wherein the enzyme digestion result generates two fragments with the sizes of about 3.5kb and about 0.5kb respectively, which indicates that the target fragment is inserted into a TOPO vector;

2. construction of plant overexpression vectors

a. Entry clone pENTR^TMConstruction of 2B-NtERF91

(1) BamH I/Xho I cleavage of pTOPO-NtERF91 and pENTR^TM2B obtaining target gene fragment NtERF91 and carrier pENTR^TM2B linearization segment, gel recovery, connection and transformation of competent cell DH5 alpha;

(2) selecting clone transformed into DH5 alpha, extracting plasmid DNA, carrying out enzyme digestion by BamH I/Xho I, wherein the enzyme digestion result is that a carrier fragment of 3.8kb and a fragment of about 0.5kb are correct clones, and the correct clones are named as pENTR^TM2B-NtNtERF91；

b. Obtaining plant expression vectors by LR reaction

(1) Entry clone pENTR^TMNtERF91 and an expression vector pK2GW7 LR react and then are transformed into escherichia coli DH5 alpha competent cells to obtain a plant expression vector pK2GW7-NtERF 91; using BamHI/Xho I enzyme digestion identification pK2GW7-NtERF91, correct clone can cut out two fragments of about 0.5kb and 11 kb;

the above LR reaction system: successfully constructed entry vector pENTR^TMNtERF91(50-150ng)1-7 μ L, 0.5 μ L degradation Vector, TE Buffer to total volume 8 μ L; mixing, ice-cooling for 2min, and flicking for 2 times; add 2. mu.L of LRClonease^TMII, flicking, uniformly mixing, centrifuging and carrying out water bath at 25 ℃ for 1 h; then adding 1 mu L of protease K for flicking, uniformly mixing, and carrying out water bath at 37 ℃ for 10 min;

B. genetic transformation of tobacco:

(1) expression vector transformation of agrobacterium

Taking out the agrobacterium-infected cells from a refrigerator at the temperature of-80 ℃, placing the cells on ice for dissolution, and adding a recombinant expression vector pK2GW7-NtERF 914 muL; quickly freezing for 1 minute by using liquid nitrogen, transferring into a water bath at 37 ℃ for 5 minutes, then performing ice bath for 2 minutes, adding 1mL of LB liquid culture medium into the mixture, and culturing at 28 ℃ and 220rpm for 3-4 hours; the culture is coated on an LB solid culture medium containing 100mg/L of spectinomycin and 25mg/L of rifampicin, and is inversely cultured for 2-3 days at 28 ℃, so that agrobacterium clones containing a target vector can be seen;

(2) tobacco transformation

a. Selecting agrobacterium clones containing a target vector, streaking on an LB (lysogeny broth) plate containing spectinomycin and rifampicin, and culturing for 2-3 days at 28 ℃; scraping streak plaque, inoculating bacteria into an MS culture medium containing spectinomycin and rifampicin, carrying out shake culture at 28 ℃ and 220rpm, centrifuging at 6,000rpm for 5 minutes when the bacterial liquid concentration reaches OD (0.5-0.8) to enrich the bacteria, removing supernatant, and suspending the bacteria by using 20mL of liquid MS culture medium to obtain agrobacterium suspension bacterial liquid containing a target carrier;

b. putting the tobacco leaves into a 500mL wide-mouth bottle, adding a proper amount of 75% ethanol, and rinsing for 1 min; ethanol was removed and 0.1% HgCl was added₂Placing the solution on a shaking table, and oscillating for 15-30 minutes at room temperature; discard HgCl₂The solution is washed with sterile water for 6 times;

c. taking out the tobacco leaves, absorbing surface liquid by using sterile absorbent paper, cutting the sterile leaves into small pieces of about 1cm multiplied by 1cm by using scissors, putting the cut tobacco leaves into sterile MS liquid culture medium suspension bacteria liquid containing a target carrier, and standing for 15-20 min; taking out tobacco leaf, removing excess bacteria solution with sterile filter paper, and dark culturing in MS culture medium containing 6-BA (0.02mg/L) and NAA (2mg/L) at 25 deg.C for two days; then, the tobacco leaves are transferred into a differentiation culture medium, and the cut contacts the culture medium to perform differentiation culture under the greenhouse condition; the differentiation culture medium is an MS culture medium containing 6-BA (0.5mg/L), NAA (0.1mg/L), kanamycin (100mg/L) and cefamycin (500mg/L), subcultured for 1 time every 2-3 weeks, callus gradually grows from the incision, and finally differentiation and sprouting are carried out;

d. cutting off buds growing to 3-5 cm, transferring the buds into an MS culture medium for inducing rooting, taking out transgenic plants after rooting, washing the culture medium with tap water, and transplanting the transgenic plants into sterilized nutrient soil;

e. the transgenic plants are subjected to PCR verification and amplification by NPTII gene specific primers (NPTII-F: TCGGCTATGACTGGGCACAACAGA, NPTII-R: AAGAAGGCGATAGAAGGCGATGCG) to identify transgenic positive plants.

9. Use of a gene NtERF91 for increasing the neonicotinoid content of tobacco lamina according to claim 8, characterized in that HgCl is 0.1%₂The solution preparation method comprises weighing 0.1 g mercuric chloride, dissolving with a little alcohol, adding water to constant volume to 100 mL.

Technical Field

The invention belongs to the technical field of genetic engineering, and particularly relates to a cloning method and application of a tobacco neonicotinoid synthesis regulatory gene NtERF 91.

Background

Neonicotinoid is an alkaloid from solanaceae plants (e.g., tobacco, tomato). In tobacco, the proportion of neonicotine in total tobacco alkaloids is low. The tobacco alkaloid accounts for 2% -4% of the total dry weight of tobacco. Among the four alkaloids in tobacco, nicotine accounts for about 95% of total alkaloids, and neonicotine, nornicotine and anabasine only account for the remaining 5%. In nature, these tobacco alkaloid compounds have biological activity and act as natural toxins in the tobacco defense system to protect insects or herbivores from predation.

Neonicotinoids are often used in animal models and cell lines to study whether they can treat nicotine addiction, alzheimer's disease, thyroiditis, multiple sclerosis, and inhibit acetylcholine receptor activity. In terms of secondary metabolism of tobacco alkaloids, transcription factor genes of the ERF (ethylene Response factor) type are considered to be important regulators in tobacco for regulating nicotine synthesis (Rushton et al, 2008, Plant Physiology,147: 280-295). The genetic locus of NIC2, which regulates nicotine synthesis, has been found to consist of at least 7 ERF genes, such as NtERF189, NtERF179, etc. (Shoji et al, 2010, Plant Cell,22: 3390-. These ERF transcription factors belong to the X subfamily of I in the ERF family, and can activate the expression of key metabolic rate-limiting enzyme genes (such as NtPMT and NtQPT) in the nicotine synthesis pathway by directly combining GCC-box in the promoter to transcriptionally activate the genes, thereby enhancing the synthesis and accumulation of nicotine (Shoji et al, 2010, plant cell,22: 3390-3409). However, neonicotinoids accumulate predominantly in tobacco suspension Cell lines, primarily due to low expression of MPO metabolizing enzymes in the nicotine synthesis pathway in suspension Cell lines (Shoji and Hashimoto,2008, Plant Cell Physiology, 49: 1209-1216). On the other hand, the neonicotinoid is used as alkaloid with less accumulation in tobacco alkaloid, and has not been reported for a transcription regulation factor gene for regulating and controlling the metabolism and accumulation of the nicotine.

Because of the medical efficacy of neonicotinoids, scientists are developing studies on improving the nicotine content of tobacco by biotechnology means, thereby increasing the commercial use of tobacco and also reducing the production cost of neonicotinoid raw materials. At present, the deep research on the synthesis regulation mechanism of the neonicotine is also urgently needed in China, and a theoretical basis is provided for cultivating tobacco varieties with high neonicotine content.

Disclosure of Invention

The first purpose of the invention is to provide a tobacco neonicotinoid synthesis regulatory gene NtERF 91; the second purpose is to provide a cloning method of the tobacco neonicotinoid synthesis regulatory gene NtERF 91; the third purpose is to provide the application of the tobacco neonicotinoid synthesis regulatory gene NtERF 91.

The first purpose of the invention is realized by that the nucleotide sequence of the tobacco neonicotinoid synthesis regulatory gene NtERF91 is shown in a sequence table SEQ ID NO: 1 is shown.

The second object of the present invention is achieved by comprising the steps of:

A. determining the sequence of the NtERF91 gene;

1 ERF family gene positively regulated by jasmonate is obtained by analyzing transcriptome data of tobacco root tissues treated by jasmonate, and the gene is NtERF91 found by sequence comparison. Designing gene cloning primers according to the gene sequence:

forward primer NtERF91-BamH I:

GGATCCATGTTAACTAGTGTCAATACCACGT；

reverse primer NtERF91-Xho I:CTCGAGTCAATTTTCAGCCAATTTTCTCTTC；

B. extracting tobacco root tissue RNA, and performing reverse transcription to obtain first-strand cDNA;

C. taking the first chain cDNA obtained by reverse transcription as a template, carrying out PCR amplification by using a NtERF91 gene cloning primer, and recovering and purifying a PCR product;

D. the purified product is connected with a carrier, and the connection system and the process are as follows: 4. mu.L of purified product, 1. mu.L of saltsolution, 1. mu.L of purified product

-Blunt II-TOPO (Invitrogen) and water bath at 25 deg.C for 30 min; passing the joined carrier through heatAnd (3) exciting and transforming Escherichia coli DH5 alpha, adding a liquid culture medium, performing shake culture, coating the liquid culture medium on an LB (Langmuir-Blodgett) plate containing 100mg/L kanamycin, performing overnight culture, selecting bacterial colonies, performing bacterial liquid culture, extracting plasmids and performing PCR (polymerase chain reaction) detection. Screening positive clones, and sequencing the positive clones.

The third purpose of the invention is realized by the application of the tobacco neonicotinoid synthesis regulatory gene NtERF91 in obtaining transgenic plants with obviously improved neonicotinoid content; namely, the tobacco nicotine synthesis regulatory gene NtERF91 is used for improving the content of the neonicotine in the tobacco leaves.

The invention obtains a tobacco neonicotinoid synthesis regulation gene NtERF91 from tobacco, which comprises the following steps: 1 ERF family gene positively regulated by jasmonate is obtained by analyzing transcriptome data of tobacco root tissues treated by jasmonate, and the gene is NtERF91 found by sequence comparison. Designing a gene specific primer according to the gene sequence information to carry out PCR reaction to obtain a target product; sequencing a target product to obtain an NtERF91 gene sequence; an Overexpression (OE) strain of the NtERF91 gene is obtained by utilizing an agrobacterium-mediated genetic transformation method, and functional identification is carried out on NtERF91, and the result shows that the NtERF91 gene has the effect of remarkably improving the accumulation amount of the neonicotinoid in tobacco leaves, and the content of the neonicotinoid in the obtained transgenic plant is more than 4 times that of the obtained transgenic plant. The tobacco NtERF91 gene has a wide application prospect in culturing the tobacco with the increased content of the neonicotine.

Drawings

FIG. 1 is an agarose gel electrophoresis chart of PCR amplification products of NtERF91 gene, wherein the size of NtERF91 is 435bp, and M is DL2000DNA Marker;

FIG. 2 shows the colony PCR detection of Agrobacterium transformation effect of recombinant over-expression vector pK2GW7-NtERF91, M is DL2000DNA Marker, and 1 and 2 are PCR products;

FIG. 3 is T₀Gene expression of transgenic plants with the gene NtERF91 and gene expression level analysis of nicotine synthesis pathway; NtERF91-OE-2, NtERF91-OE-4, NtERF91-OE-5 are transgenic strains, EV is a transgenic empty vector control, A is NtPMT, B is NtQPT, C is NtAO, D is NtMPO, E is NtA622, F is NtQS, G is NtODC, and H is NtADC;

FIG. 4 is a drawing showingT₀Analyzing the content of the neonicotinoid in the tobacco leaves of transgenic plants of the NtERF91 gene; NtERF91-OE-2, NtERF91-OE-4, NtERF91-OE-5 are transgenic strains, A is an upper leaf, B is a middle leaf, C is a lower leaf, I is a trans-empty vector control EV, II is an NtERF91-OE-2 transgenic strain, III is an NtERF91-OE-4 transgenic strain, IV is an NtERF91-OE-5 transgenic strain, and ". mark" shows that the difference between the content of the anabasine in the plant and the content of the non-empty control EV is significant at the level of 0.05. .

Detailed Description

The present invention is further illustrated by the following examples and the accompanying drawings, but the present invention is not limited thereto in any way, and any modifications or alterations based on the teaching of the present invention are within the scope of the present invention.

The nucleotide sequence of the tobacco neonicotinoid synthesis regulatory gene NtERF91 is shown in a sequence table SEQ ID NO: 1 is shown.

The amino acid sequence of the tobacco neonicotinoid synthesis regulatory gene NtERF91 is shown as SEQ ID NO: 2, respectively.

The cloning method of the tobacco neonicotinoid synthesis regulatory gene NtERF91 is characterized by comprising the following steps of:

A. determining the sequence of the NtERF91 gene;

1 ERF family gene positively regulated by jasmonate is obtained by analyzing the transcriptome data of the tobacco root tissue after jasmonate treatment, and the gene is NtERF91 found by sequence comparison. Designing gene cloning primers according to the gene sequence:

forward primer NtERF91-BamH I:

GGATCCATGTTAACTAGTGTCAATACCACGT；

reverse primer NtERF91-Xho I: 5' -CTCGAGTCAATTTTCAGCCAATTTTCTCTTC；

B. Extracting tobacco root tissue RNA, and performing reverse transcription to obtain first-strand cDNA;

C. taking the first chain cDNA obtained by reverse transcription as a template, carrying out PCR amplification by using a NtERF91 gene cloning primer, and recovering and purifying a PCR product;

D. the purified product is linked to a carrier and reacted with a reagent kitShould be linked to the TOPO vector, the linking system and procedure are as follows: 4 μ L of purified product, 1 μ L of salt solution, 1 μ L

Mixing with Blunt II-TOPO, and water bathing at 25 deg.C for 30 min; and transforming the connected vector into escherichia coli through heat shock, adding a liquid culture medium for shake culture, coating the escherichia coli onto an LB (lysogeny broth) flat plate containing 100mg/L kanamycin for overnight culture, selecting a bacterial colony for culture, extracting plasmids from 2mL of bacterial liquid, and carrying out plasmid PCR (polymerase chain reaction) detection. Screening positive clones, and sequencing the positive clones.

And C, selecting a Phusion high-fidelity amplification enzyme reaction system as a PCR amplification reaction system in the step C, wherein the total volume of the system is 50 mu L, and the method comprises the following steps: 200ng cDNA, 10. mu.L of 5 XPPhusion HF reaction buffer, 1. mu.L of 10mM dNTP, 2U

High-Fidelity DNA Polymerase, 1. mu.L each of 10. mu.M forward and reverse primers, and water was added to 50. mu.L.

The reaction conditions for PCR amplification in step C are

The pro amplification instrument is used for carrying out the following reaction procedures: 30 seconds at 98 ℃; 35 cycles of 98 ℃, 7 seconds, 58 ℃, 30 seconds, 72 ℃, 30 seconds; extension at 72 ℃ for 7 min;

the application of the tobacco neonicotinoid synthesis regulatory gene NtERF91 is the application of the tobacco neonicotinoid synthesis regulatory gene NtERF91 in obtaining transgenic plants with obviously improved tobacco leaf nicotine content.

The method for obtaining the transgenic plant with the tobacco leaf neonicotine content remarkably improved comprises the following steps:

A. construction of an overexpression vector

(1) Taking cDNA of root tissues of a tobacco variety Coker176 as a template, amplifying by using a gene specific primer to obtain a gene fragment with the size of about 0.5kb, and purifying and recycling;

(2) the recovered NtERF91 gene fragment was subjected to TOPO cloning and ligated to

Transforming Escherichia coli DH5 alpha competent cells after Blunt II-TOPO (3.5kb) vector, extracting plasmid for PCR detection, selecting plasmid with amplification product size of about 0.5kb to extract DNA, and the constructed vector is named as pTOPO-NtERF 91;

(3) because the forward and reverse primers of the gene are respectively provided with recognition sites of BamH I and Xho I, the two enzymes are selected to carry out double enzyme digestion detection on a plasmid DNA sample, and the enzyme digestion result generates two fragments with the sizes of about 3.5kb and about 0.5kb respectively, which indicates that a target fragment is inserted into a TOPO vector;

2. construction of plant overexpression vectors

a. Entry clone pENTR^TMConstruction of 2B-NtERF91

(1) BamH I/Xho I digestion of pTOPO-NtNtERF91 and pENTR^TM2B obtaining target gene fragment NtERF91 and carrier pENTR^TM2B linearization segment, gel recovery, connection and transformation of competent cell DH5 alpha;

(2) selecting clone transformed into DH5 alpha, extracting plasmid DNA, carrying out enzyme digestion by BamH I/Xho I, wherein the enzyme digestion result is that a carrier fragment of 3.8kb and a fragment of about 0.5kb are correct clones, and the correct clones are named as pENTR^TM2B-NtERF91；

b. Obtaining plant expression vectors by LR reaction

(1) Entry clone pENTR^TMNtERF91 and expression vector pK2GW7 LR react and then transform Escherichia coli DH5 alpha competent cells to obtain plant expression vector pK2GW7-NtERF 91. Using the BamH I/Xho I cleavage to identify pK2GW7-NtNtERF91, the correct clone cut out two fragments of approximately 0.5kb and 11 kb.

The above LR reaction system: successfully constructed entry vector pENTR^TMNtERF91(50-150ng)1-7 μ L, 0.5 μ L degradation Vector, TE Buffer to total volume 8 μ L; mixing, ice-cooling for 2min, and flicking for 2 times; add 2. mu.L of LRClonease^TMII, flicking, uniformly mixing, centrifuging and carrying out water bath at 25 ℃ for 1 h; then adding 1 mu L of protease K for flicking, uniformly mixing, and carrying out water bath at 37 ℃ for 10 min;

B. genetic transformation of tobacco:

(1) expression vector transformation of agrobacterium

Taking out the agrobacterium-infected cells from a refrigerator at the temperature of-80 ℃, placing the cells on ice for dissolution, and adding a recombinant expression vector pK2GW7-NtERF 914 muL; quickly freezing for 1 minute by using liquid nitrogen, transferring into a water bath at 37 ℃ for 5 minutes, then performing ice bath for 2 minutes, adding 1mL of LB liquid culture medium into the mixture, and culturing at 28 ℃ and 220rpm for 3-4 hours; the culture is coated on an LB solid culture medium containing 100mg/L of spectinomycin and 25mg/L of rifampicin, and is inversely cultured for 2-3 days at 28 ℃, so that agrobacterium clones containing a target vector can be seen;

(2) tobacco transformation

a. Selecting agrobacterium clones containing a target vector, streaking on an LB (lysogeny broth) plate containing spectinomycin and rifampicin, and culturing for 2-3 days at 28 ℃; scraping streak plaque, inoculating bacteria into an MS culture medium containing spectinomycin and rifampicin, carrying out shake culture at 28 ℃ and 220rpm, centrifuging at 6,000rpm for 5 minutes when the bacterial liquid concentration reaches OD (0.5-0.8) to enrich the bacteria, removing supernatant, and suspending the bacteria by using 20mL of liquid MS culture medium to obtain agrobacterium suspension bacterial liquid containing a target carrier;

b. putting the tobacco leaves into a 500mL wide-mouth bottle, adding a proper amount of 75% ethanol, and rinsing for 1 min; ethanol was removed and 0.1% HgCl was added₂Placing the solution on a shaking table, and oscillating for 15-30 minutes at room temperature; discard HgCl₂The solution is washed with sterile water for 6 times;

c. taking out the tobacco leaves, absorbing surface liquid by using sterile absorbent paper, cutting the sterile leaves into small pieces of about 1cm multiplied by 1cm by using scissors, putting the cut tobacco leaves into sterile MS liquid culture medium suspension bacteria liquid containing a target carrier, and standing for 15-20 min; taking out tobacco leaf, removing excess bacteria solution with sterile filter paper, and dark culturing in MS culture medium containing 6-BA (0.02mg/L) and NAA (2mg/L) at 25 deg.C for two days; then, the tobacco leaves are transferred into a differentiation culture medium, and the cut contacts the culture medium to perform differentiation culture under the greenhouse condition; the differentiation culture medium is an MS culture medium containing 6-BA (0.5mg/L), NAA (0.1mg/L), kanamycin (100mg/L) and cefamycin (500mg/L), subcultured for 1 time every 2-3 weeks, callus gradually grows from the incision, and finally differentiation and sprouting are carried out;

d. cutting off buds growing to 3-5 cm, transferring the buds into an MS culture medium for inducing rooting, taking out transgenic plants after rooting, washing the culture medium with tap water, and transplanting the transgenic plants into sterilized nutrient soil;

e. the transgenic plants are subjected to PCR verification and amplification by NPTII gene specific primers (NPTII-F: TCGGCTATGACTGGGCACAACAGA, NPTII-R: AAGAAGGCGATAGAAGGCGATGCG) to identify transgenic positive plants.

The 0.1% of HgCl₂The solution preparation method comprises weighing 0.1 g mercuric chloride, dissolving with a little alcohol, adding water to constant volume to 100 mL.

The invention is further illustrated by the following specific examples: