CN112273399B

CN112273399B - Application of phytophthora capsici effector factor RxLR19781 in promoting plant growth

Info

Publication number: CN112273399B
Application number: CN202011053242.9A
Authority: CN
Inventors: 张修国; 盛慧; 朱春原; 杨灿灿; 艾聪聪
Original assignee: Shandong Agricultural University
Current assignee: Shandong Agricultural University
Priority date: 2020-09-29
Filing date: 2020-09-29
Publication date: 2021-06-29
Anticipated expiration: 2040-09-29
Also published as: CN112273399A

Abstract

The invention discloses application of a phytophthora capsici effector RxLR19781 in promoting plant growth. The invention utilizes protein expression technology to prepare the phytophthora capsici effector RxLR19781 escherichia coli high-efficiency expression strain to obtain an RxLR19781 protein solution, and further proves that the RxLR19781 has the performance of promoting the growth and the vigor of roots of pepper, cucumber and tomato seedlings, and is expected to be developed into a novel protein preparation for strengthening the roots and the seedlings of vegetables.

Description

Application of phytophthora capsici effector factor RxLR19781 in promoting plant growth

Technical Field

The invention relates to the technical field of biology, in particular to application of phytophthora capsici effector RxLR19781 in promoting plant growth.

Background

Under natural conditions, plants are subjected to various biotic and abiotic stresses for a long time, and various defense means have been developed for plants in order to avoid these disturbances. When the pathogenic bacteria invade the plant cells, barrier reaction is often formed on the surfaces of the plant cells to prevent the invasion of the pathogenic bacteria, and if the pathogenic bacteria successfully break through the barrier on the surfaces of the plant cells, the plant cell membrane receptor can sense the invasion of the pathogenic bacteria, so that the immune system of the plant is started, and the host plant is induced to generate immune reaction.

Researches show that during the infection of plant hosts by plant pathogenic bacteria, RxLR effector factors are often secreted and generated, the RxLR effector factors are combined with host target proteins to interfere the immune system of the plants and promote the infection and the pathogenicity of the pathogenic bacteria, but host plants also correspondingly evolve a defense system to recognize and prevent the infection and the pathogenicity of the pathogenic bacteria, so that the expression of plant resistance proteins, the burst of active oxygen, the deposition of callose and even the generation of allergic necrosis reaction (HR) are stimulated, and the expansion of pathogenic oomycetes is inhibited. Such RxLR effectors are often referred to as immune effector molecules.

In recent years, researches show that genomes of important plant pathogenic oomycetes, namely potato late blight (Phytophthora sojae), Phytophthora sojae (Phytophthora sojae), Phytophthora nicotianae (Phytophthora parasitica) and Phytophthora capsici (Phytophthora capsicii) contain hundreds of RxLR effect factors, wherein some RxLR effect molecule members have immune performance, the immune characteristics of RxLR effect molecules are cloned and correctly identified, and the application prospect of the immune RxLR effect molecules is further proved to have important significance by means of gene expression and protein purification technology.

Disclosure of Invention

The invention aims to provide application of phytophthora capsici effector RxLR19781 in promoting plant growth.

In order to achieve the object of the present invention, in a first aspect, the present invention provides the use of phytophthora capsici effector RxLR19781 for promoting plant growth.

The effector factor RxLR19781 of the invention was cloned from Phytophthora capsici strain SD33, see CN 110734918A.

In the application, the phytophthora capsici effector RxLR19781 is prepared into protein solution, or the Escherichia coli liquid expressing the phytophthora capsici effector RxLR19781 or the diluent thereof is applied to soil or seedling culture medium around plant rhizosphere.

In the application, the phytophthora capsici effector RxLR19781 is prepared into a protein solution, or the strain is subjected to root irrigation treatment by using an escherichia coli bacterial liquid expressing the phytophthora capsici effector RxLR19781 or a diluent thereof.

In the application, the phytophthora capsici effector RxLR19781 is prepared into a protein solution, or the Escherichia coli liquid expressing the phytophthora capsici effector RxLR19781 or a diluent thereof is subjected to seed soaking treatment.

In the application, the coding gene of the phytophthora capsici effector RxLR19781 is introduced into a plant through a plasmid or is integrated on a plant chromosome through a genetic engineering means, so that the plant expresses the phytophthora capsici effector RxLR 19781.

In the invention, the Escherichia coli expressing the phytophthora capsici effector RxLR19781 is obtained by introducing a phytophthora capsici effector RxLR19781 encoding gene into an Escherichia coli competent cell through a plasmid.

Preferably, the plasmid is pET28 a.

Preferably, the E.coli competent cell is DH5 alpha.

In the present invention, the plants include, but are not limited to, pepper, cucumber, and tomato.

In a second aspect, the invention provides an application of a phytophthora capsici effector RxLR19781 and a prokaryotic or eukaryotic expression system for expressing the phytophthora capsici effector RxLR19781 in preparing a plant growth promoter.

In a third aspect, the invention provides a plant growth promoter, the active ingredients of which are phytophthora capsici effector RxLR19781 and/or a prokaryotic or eukaryotic expression system expressing the phytophthora capsici effector RxLR 19781.

By the technical scheme, the invention at least has the following advantages and beneficial effects:

the invention utilizes protein expression technology to prepare the phytophthora capsici effector RxLR19781 escherichia coli high-efficiency expression strain to obtain an RxLR19781 protein solution, and further proves that the RxLR19781 has the performance of promoting the growth and the vigor of roots of pepper, cucumber and tomato seedlings, and is expected to be developed into a novel protein preparation for strengthening the roots and the seedlings of vegetables.

Drawings

FIG. 1 is a map of pET28a vector.

FIG. 2 shows the result of PCR amplification of RxLR19781 gene in a preferred embodiment of the present invention. Wherein, M: DNA Marker, 1-8: the RxLR19781 gene DNA PCR amplified band.

FIG. 3 is a SDS-PAGE gel of RxLR19781 expression in a preferred embodiment of the invention. Wherein, M: a protein Marker; 1-3: IPTG induces RxLR19781 protein expression; CK: and (6) comparison.

FIG. 4 shows that RxLR19781 protein promotes root development of pepper seedlings in a preferred embodiment of the present invention.

FIG. 5 shows that RxLR19781 protein promotes root growth of pepper seedlings in a preferred embodiment of the present invention.

FIGS. 6 and 7 show that the RxLR19781 protein promotes the root development of cucumber seedlings in the preferred embodiment of the invention.

FIG. 8 shows that in the preferred embodiment of the present invention, RxLR19781 protein promotes root development of tomato seedlings.

FIG. 9 shows that RxLR19781 protein promotes tomato seedling growth in a preferred embodiment of the present invention.

Detailed Description

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention. Unless otherwise indicated, the examples follow conventional experimental conditions, such as the Molecular Cloning handbook, Sambrook et al (Sambrook J & Russell DW, Molecular Cloning: a Laboratory Manual, 2001), or the conditions as recommended by the manufacturer's instructions.

Example 1 cloning and expression of Phytophthora capsici Effector RxLR19781 Gene

1. Phytophthora capsici effector molecule RxLR19781 gene information prediction

By means of bioinformatics DNAMAN software, the whole genome https:// genome. jgi. doe. gov/portal/, phytophthora capsici was analyzed and compared, and 1 important RxLR effector molecule was screened and defined, which is named as RxLR19781 effector, and the encoded gene of the effector molecule has the size of 366bp (containing a signal peptide of 57bp), contains 121 amino acid residues, has the molecular weight of 13.86KDa, and has the pI of 6.87. SignalP 4.0Server (http:// www.cbs.dtu.dk/services/SignalP /) was used to predict signal peptide, which has a signal peptide region of 1-57bp and no transmembrane region.

2. Phytophthora capsici effector molecule RxLR19781 gene clone sequencing

2.1 strains of Phytophthora capsici

The highly pathogenic phytophthora capsici strain SD33 is provided by vegetable pest biology focus laboratory of Shandong university of agriculture.

2.2 RNA extraction and reverse transcription of cDNA from the strain of Phytophthora capsici SD33

The strong pathogenic strain SD33 preserved in the laboratory is cultured by using a V8 plate in a constant temperature incubator at 28 ℃, and the RNA extraction steps are as follows:

1) grinding a sample: grinding phytophthora capsici SD33 mycelia into powder by using a mortar precooled by liquid nitrogen;

2) homogenizing: taking 1g of mycelium ground powder, adding 10mL of Trizol, fully homogenizing for 2min by an electric vortex instrument, standing for 3-5min at room temperature to fully crack;

3) centrifuging at 12000rpm at 4 deg.C for 10min, sucking supernatant and removing precipitate;

4) adding chloroform into 200 mu L chloroform/mL Trizol, shaking and mixing uniformly (a vortex shaking instrument is not used), standing for 15min at 25 ℃, and centrifuging for 15min at the rotation speed of 13000rpm at 4 ℃;

5) absorbing the upper water phase into a new centrifugal tube, discarding the lower phenol phase without absorbing the middle interface, wherein the phenol phase is used for extracting protein;

6) adding 500 mu L of isopropanol into 1mL of Trizol, reversing, and standing at room temperature for 5-10 min;

7) centrifuging at 4 deg.C and 12000rpm for 10min, and removing supernatant;

8) adding ethanol according to the proportion of 1mL of 75% ethanol/mL of Trizol, gently inverting, centrifuging at the temperature of 4 ℃ and the rotation speed of 8000rpm for 5min, and removing the supernatant as much as possible;

9) standing at room temperature, air drying or oven drying for 5-10min, removing ethanol, and preventing RNA sample from drying excessively or dissolving;

10) using 50 μ L H₂O, TE buffer solution or 0.5% SDS, treating the solvent with DEPC, and autoclaving at 121 deg.C for 30 min;

11) OD measurement using ultraviolet spectrophotometry₆₀₀，A₂₆₀/A₂₈₀1.8-2.0，A₂₆₀/A₂₃₀1.8-2.2, which shows that the purity of RNA meets the experimental requirements.

Synthesizing cDNA by reverse transcription of RNA, and the process is as follows:

1) RNA reverse transcription is carried out on the RNA, an RNase removing centrifugal tube is prepared into a PCR system, and the preparation system is shown in table 1.

TABLE 1 RT-PCR reaction System

Sucking, beating and mixing after mixing, centrifuging and placing on ice.

2) Incubating at 50 deg.C for 15min, incubating at 85 deg.C for 2min, and immediately subjecting the product to PCR reaction, or storing at-20 deg.C for half a year; the long-term preservation is recommended to be carried out after subpackaging and then storing in a freezer at the temperature of-80 ℃, and repeated freeze thawing of cDNA is avoided.

2.3RxLR19781 Gene PCR cloning primer design

A pair of specific primers is designed according to the sequence of the RxLR19781 gene (minus the signal peptide sequence) in phytophthora capsici whole genome https:// genome.jgi.doe.gov/portal/recombinant vector pET28a (Novagen company), two enzyme cutting sites NcoI and NotI:

the upstream primer RxLR 19781F: 5'-CATGCCATGGCTGTCGACACAAGCTGACGCCAC-3'

Downstream primer RxLR 19781R: 5'-ATAAGAATGCGGCCGCGTAAGGAAGTCCTTTCTTG-3'

For later purification of RxLR19781 protein, the C-terminal his tag of pET28a vector was ensured to be translated normally, and the stop codon of RxLR19781 was removed. The primer is synthesized by Qingdao Optimaxi biotechnology Limited. The map of the pET28a vector is shown in FIG. 1.

2.4 PCR amplification of the RxLR19781 Gene of order

The target fragment was amplified from the cDNA by polymerase chain reaction, the PCR reaction system is shown in Table 2.

TABLE 2 RxLR19781 Gene PCR amplification System

The PCR amplification product is shown by agarose gel electrophoresis (figure 2), and the amplification band is about 300bp and is basically consistent with the size of the target gene band. The PCR amplified target gene fragment is recovered by using a gel recovery kit (DNA recovery kit), and the recovered product can be stored for later use at the temperature of minus 20 ℃ for a short time. The PCR amplification result of the target RxLR19781 gene is shown in FIG. 2.

3. Recombinant vector construction

3.1 double digestion of target Gene and vector

The RxLR19781 gene PCR amplification gel recovery product and the vector pET28a are subjected to double enzyme digestion by enzyme 1(NcoI) and enzyme 2(XhoI) respectively, the water bath is carried out at 37 ℃ for 2-3 h, and the enzyme digestion system is shown in Table 3. The RxLR19781 and the vector pET28a after the enzyme digestion are recovered by a gel recovery kit, and the double-enzyme digestion reaction system is shown in Table 3.

TABLE 3RxLR19781 and vector pET28a double digestion reaction System

3.2 connection of the target Gene RxLR19781 to the vector pET28a

The digested RxLR19781 gene DNA fragment was recovered from pET28a (Novagen) and ligated with solution I (solution I) at 16 ℃ for 3 hours, as shown in Table 4.

TABLE 4 RxLR19781 ligation into vector pET28a reaction System

3.3 transformation of the recombinant vector pET28a into E.coli DH 5. alpha. competent cells

1) Melting 50 μ L DH5 α competent cells in ice bath, adding ligation product, mixing gently, and ice-cooling for 30 min;

2) carrying out water bath heat shock for 90s at 42 ℃, and then rapidly carrying out ice bath on the centrifugal tube for 2 min;

3) adding 500 mu L of sterile LB culture medium (without antibiotics) into each centrifuge tube on a super clean bench, uniformly mixing, placing at 37 ℃, performing shaking culture at 200rpm for 45-60 min, and ensuring that host bacteria are completely recovered;

4) centrifuging for 1min at 8000rpm of a normal temperature centrifuge, discarding part of supernatant, resuspending with a pipette thallus, uniformly mixing, coating on an LB agar culture medium (containing corresponding antibiotics), and then performing inverted culture in an incubator at 37 ℃ for 12-16 h.

3.4 identification of the recombinant vector pET28a

After bacterial plaque grows on the plate by the prepared competent cells, adding 1mL of sterile LB liquid medium (containing corresponding antibiotics) into a 1.5mL centrifuge tube, selecting the grown single bacterial colony, placing the single bacterial colony in the LB liquid medium centrifuge tube, carrying out shake culture at 37 ℃ for 5-6 h to serve as a bacterial liquid PCR template, and carrying out bacterial liquid PCR identification at proper time, wherein a bacterial liquid PCR reaction system is shown in Table 5.

TABLE 5 PCR reaction System for recombinant vector pET28a bacterial liquid

And (3) carrying out agarose gel electrophoresis identification on the bacteria liquid PCR reaction sample, taking the bacteria liquid with the PCR amplification result as a positive sample, taking 500 mu L of the bacteria liquid with the positive sample, sending the bacteria liquid to Qingdao Tinxi biological Limited company for sequencing, comparing and analyzing the sequencing result with a genome sequence by using DNAman software, taking 500 mu L of the bacteria liquid with the correct sequencing result, adding 500 mu L of 50% sterilized glycerol, storing in a freezer at the temperature of-20 ℃, taking the bacteria liquid with the correct sequencing result, extracting plasmids, and storing in a freezer at the temperature of-20 ℃ for later use, wherein the plasmid extraction is carried out according to the instruction of the CWBIO high-purity plasmid small-extraction kit.

RxLR19781 recombinant protein expression

4.1RxLR19781 recombinant protein test expression

1) The pET28a recombinant plasmid with correct sequencing is transformed into an E.coli Rosetta (DE3) strain, centrifuged for 1min at 8000rpm of a normal-temperature centrifuge, a part of supernatant is discarded, a pipettor is used for carrying out heavy suspension, the mixture is uniformly mixed and then coated on an LB agar plate culture medium (containing corresponding antibiotics), and then the inverted culture is carried out for 12 to 16 hours in an incubator at 37 ℃;

2) selecting a single bacterial strain, inoculating the single bacterial strain into a centrifugal tube filled with 1.5mL of LB liquid medium (added with Kan resistance), and carrying out shake culture at 37 ℃ and 180rpm for 6 h;

3) inoculating 1mL of shake culture solution into LB liquid culture medium (adding Kan resistance) containing 1.5mL, and culturing to OD₆₀₀Taking 1mL of bacterial liquid as a control before induction, wherein the bacterial liquid is 0.6-0.8;

4) adding Inducer (IPTG) with different concentrations into the induced bacteria liquid and the control bacteria liquid respectively, and inducing at 37 ℃ and 180rpm for 3 h;

5) after induction, 1mL of bacterial liquid is taken respectively, and is centrifuged for 1min at 12000rpm simultaneously with the control; discarding the supernatant, adding 40 μ L of 2 × binding buffer solution respectively, resuspending and mixing, then adding 40 μ L of 2 × loading buffer solution, and mixing;

6) boiling the sample for 15min, oscillating for 1 time at 5min intervals, oscillating for 2 times, and centrifuging at 12000rpm for 1min before SDS-PAGE electrophoresis;

7) taking 20 mu L of sample to carry out SDS-PAGE electrophoresis, observing the expression condition of the target protein, and determining that the appropriate concentration of an Inducer (IPTG) is 0.5 mM;

8) taking 500 mu L of the expression target protein bacterial liquid, adding 500 mu L of 50% sterilized glycerol, mixing uniformly, filling into a sterilized freezing storage tube, and storing in a freezer at the temperature of-20 ℃.

And then detecting the expression condition of the target protein by using SDS-PAGE electrophoresis technology, wherein SDS-PAGE electrophoresis results show that, compared with a control, after pET28a-RxLR19781 protein is induced by a proper concentration Inducer (IPTG), RxLR19781 is induced to express a protein with a molecular weight of 13.86KDa (signal peptide is removed), the molecular weight of the protein is consistent with the predicted molecular weight of RxLR19781, and the result shows that pET28a-RxLR19781 protein prokaryotic expression system is successfully constructed, and the result is shown in figure 3.

4.2 Large expression of RxLR19781 fusion protein

1) Activating the preserved strain with higher expression level, inoculating the strain into 1L LB liquid culture medium containing 50mg/mL Kan according to the proportion of 1:100, and performing shake culture at 37 ℃ and 180rpm for 3-4 h to ensure the OD of the strain₆₀₀＝0.6～0.8；

2) Ensuring the temperature of the shaking table to be reduced to 16 ℃ in advance, adding an Inducer (IPTG) with the final concentration of 1mM, and inducing at the temperature of 16 ℃ for 16-21 h overnight at 120rpm to ensure OD₆₀₀The value is 1.8-2.0, the OD value is monitored by using an ultraviolet spectrophotometer when the induction time reaches 16 hours, and the OD value is monitored for 1 time every 1 hour;

OD value: the optical density of the protein to be detected is shown, and 1OD Escherichia coli ≈ 10⁸-10⁹Cell/ml.

Example 2 application of RxLR19781 protein in promotion of root development and seedling growth of pepper, cucumber and tomato seedlings

1. Technology for promoting root development and seedling growth of pepper, cucumber and tomato seedlings by using RxLR19781 protein

1) OD was monitored by preparing a large amount of bacterial suspension containing RxLR19781 protein by induction according to the method of example 1₆₀₀The value is about 1.8-2.0, and the product is stored overnight at 4 ℃ and is used for seedling pre-treatment of pepper, cucumber and tomato seeds.

2) OD reduction with sterile Water₆₀₀Diluting the bacterial suspension with the value of 1.8-2.0 by 2-3 times, before seedling raising of pepper, cucumber and tomato seeds, applying the diluted solution to a seedling raising substrate (wood chips are used as a main substrate, and a mixture of dried chicken manure and fermented dried pig manure with the mass ratio of 1:1 is used as an organic fertilizer source and is arranged according to the volume ratio5 treatments are carried out, and the nutrient content is N0.3g/kg and P are added₂O₅0.5 g/kg and K₂O1.5 g/kg of a quick-acting chemical fertilizer), the amount of the diluted solution of the bacterial suspension, i.e., 100ml of the seedling substrate, 100kg, and the bacterial solution of DH5 α transformed with the empty vector of pET28a was induced by IPTG to serve as a Control (CK).

2. Analysis of results of RxLR19781 protein solution on promotion of root development and growth of pepper, cucumber and tomato seedlings

1) The analysis of the results of the RxLR19781 protein on the promotion of the root development and the growth of pepper seedlings is shown in FIG. 4 and FIG. 5.

Comparative analysis the results in FIG. 4 show that the average length of the young root is 4.6cm (statistics of 30 seedling root systems) in the 5-leaf stage of the pepper seedlings treated with the RxLR19781 protein, while the average length of the young root is 2.5cm (statistics of 30 seedling root systems) in the 5-leaf stage of the pepper seedlings treated with the control CK, the former is 2.1cm longer than the latter.

Comparative analysis the results in FIG. 5 show that at the 6-leaf stage of pepper seedlings treated with RxLR19781 protein, the average height of the seedlings was 10.5cm (30 statistical seedlings height), while at the 6-leaf stage of pepper seedlings treated with control CK, the average height of the seedlings was 7.5cm (30 statistical seedlings height), the average height of the former was increased by 3cm compared with the average height of the latter roots. Therefore, the RxLR19781 protein can obviously promote the development and growth of the root system of the pepper seedling.

2) The analysis of the RxLR19781 protein on the root development of cucumber seedlings and the growth results thereof are shown in FIGS. 6 and 7.

Comparative analysis the results in FIG. 6 show that at 5-leaf stage of cucumber seedlings treated with RxLR19781 protein, the average length of the radicle is 3.5cm (statistics of 30 seedling root systems), while at 5-leaf stage of cucumber seedlings treated with control CK, the average length of the radicle is 2.0cm (statistics of 30 seedling root systems), the former is increased by 1.5cm compared with the latter.

The results of comparative analysis in FIG. 7 show that the mean height of seedlings at 6 leaf stage of cucumber seedlings treated with RxLR19781 protein is 13.5cm (30 statistical seedlings are high), while the mean height of seedlings at 6 leaf stage of cucumber seedlings treated with control CK is 11.5cm (30 statistical seedlings are high), the mean height of the seedlings is increased by 2cm compared with the mean height of roots of the latter cucumber seedlings, and the RxLR19781 protein can obviously promote the development and growth of roots of cucumber seedlings.

3) The analysis of the results of the development of RxLR19781 protein into tomato seedling root system and its growth is shown in FIG. 8 and FIG. 9.

Comparative analysis the results in FIG. 8 show that the mean length of the young roots is 3.8cm (statistics of 30 seedling root systems) in the 5-leaf stage of tomato seedlings treated with RxLR19781 protein, while the mean length of the young roots is 1.8cm (statistics of 30 seedling root systems) in the 5-leaf stage of tomato seedlings treated with control CK, the former is 2cm longer than the latter.

Comparative analysis the results in FIG. 9 show that the mean height of seedlings at 6 leaf stage of tomato seedlings treated with RxLR19781 protein was 14.5cm (statistics for 30 seedling heights), while the mean height of seedlings at 6 leaf stage of control CK-treated tomato seedlings was 11.5cm (statistics for 30 seedling heights), the former increased by 3cm compared to the latter. Therefore, the RxLR19781 protein can obviously promote the development and growth of tomato seedling root systems.

Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims

1. Phytophthora capsici effector RxLR19781 and prokaryotic or eukaryotic expression system for expressing the Phytophthora capsici effector RxLR19781 are applied to promoting plant growth.

2. The use according to claim 1, wherein the phytophthora capsici effector RxLR19781 is formulated as a protein solution, or the escherichia coli bacterial solution expressing the phytophthora capsici effector RxLR19781 or a dilution thereof is applied to the soil around the rhizosphere of plants or a seedling raising substrate.

3. The use as claimed in claim 1, wherein the phytophthora capsici effector RxLR19781 is formulated into a protein solution, or the strain is subjected to root irrigation treatment with an escherichia coli solution or a dilution thereof expressing the phytophthora capsici effector RxLR 19781.

4. The use as claimed in claim 1, wherein the Phytophthora capsici effector RxLR19781 is formulated into a protein solution, or a strain of E.coli strain expressing the Phytophthora capsici effector RxLR19781 or a dilution thereof is subjected to seed soaking.

5. The use as claimed in claim 1, wherein the gene encoding the Phytophthora capsici effector RxLR19781 is introduced into plants by plasmids or integrated into plant chromosomes by genetic engineering means, so that the plants express the Phytophthora capsici effector RxLR 19781.

6. The use according to any one of claims 2 to 4, wherein the E.coli expressing the Phytophthora capsici effector RxLR19781 is obtained by introducing a gene encoding the Phytophthora capsici effector RxLR19781 into E.coli competent cells by means of a plasmid.

7. The use according to claim 6, wherein the plasmid is pET28 a; and/or

The Escherichia coli competent cell is DH5 alpha.

8. Use according to claim 1, wherein the plants comprise capsicum, cucumber and tomato.

9. The phytophthora capsici effector factor RxLR19781 and a prokaryotic or eukaryotic expression system for expressing the phytophthora capsici effector factor RxLR19781 are applied to the preparation of plant growth promoters.