CN116083334A - Method for improving PGPR rhizosphere chemotactic colonization capacity and engineering bacteria - Google Patents

Abstract

The invention belongs to the field of molecular biology, relates to plant rhizosphere growth promoting bacteria (PGPR), and particularly relates to a method for improving the chemotactic colonization capacity of the rhizosphere of the PGPR and engineering bacteria. The present application finds that at least one of the bacterial chemotactic receptors has a C-terminal extension containing a pentapeptide which is capable of mediating the interaction of methyltransferases CheR and methylesterases CheB involved in chemotaxis, and reversibly methylates the chemotactic receptor. Grafting the pentapeptide to the C-terminal of the chemotactic receptor of the strong chemotactic substance of the PGPR chemotactic rhizosphere can enhance the chemotactic response of the pentapeptide to the strong chemotactic substance, thereby realizing the improvement of the chemotactic and colonial capacity of the PGPR rhizosphere.

Description

A method for improving PGPR rhizosphere chemotactic colonization ability and engineering bacteria

technical field

The invention belongs to the field of molecular biology and relates to plant rhizosphere growth-promoting bacteria (PGPR), in particular to a method and engineering bacteria for improving the rhizosphere chemotactic colonization ability of PGPR.

Background technique

Plant rhizosphere growth-promoting bacteria (PGPR) used in microbial fertilizers promote plant growth through multiple functions, including nitrogen fixation, phosphorus and potassium dissolution, synthesis of various plant hormones and biocontrol, and degradation of ethylene precursors synthesized by plants 1-Aminocyclopropane-1-carboxylic acid (ACC), which reduces the synthesis of ethylene in plants and enhances the adaptability of plants to stress conditions. Therefore, the use of microbial fertilizer is an effective way to reduce the amount of chemical fertilizers and pesticides.

However, there is a problem of unstable growth-promoting effect of microbial fertilizer in field application, which greatly limits the popularization and application of bacterial fertilizer. An important reason for the unstable growth-promoting effect of microbial fertilizers in field applications is the weak rhizosphere chemotactic competitiveness of strains. Identifying strong chemoattractants of PGPR in root exudates and applying genetic engineering technology to modify PGPR to improve its chemotactic competitiveness in plant rhizosphere are the main means to solve the instability of PGPR's growth-promoting effect. Once the strong chemoattractant of PGPR chemoattractant rhizosphere is determined, we can use genetic engineering technology to improve the ability of PGPR to chemoattract this component, such as enhancing the affinity of the chemoattractant chemoattractant receptor, enhancing the chemoattractant receptor affinity of the chemoattractant Methylation modification efficiency, increasing the abundance of chemotactic receptors of the chemoattractant and increasing the metabolic rate of the chemoattractant, etc., thereby improving the rhizosphere chemotactic competitiveness of PGPR, and improving and stabilizing the use effect of PGPR. Patent CN110218736A improves the expression of AcdS gene, AcdS enzyme activity and ACC metabolic rate of PGPR bacteria by replacing the promoter through homologous recombination, thereby improving the chemotaxis of PGPR bacteria to ACC; pectin-related sugars to improve the growth-promoting effect of PGPR bacteria; and during the research process, our research group found that the chemotaxis behavior of bacteria is closely related to the methylation modification of their chemotactic receptors. To explore the method of international chemotactic colonization ability, our research group conducted the following research.

Contents of the invention

The present invention proposes a method and engineering bacteria for improving the rhizosphere chemotactic colonization ability of PGPR, and finds that the C-terminal extension region of at least one chemotactic receptor in the bacterial chemotactic receptor contains a pentapeptide, and the pentapeptide It can mediate the interaction between the methyltransferase CheR and the methylesterase CheB involved in chemotaxis, and reversibly methylate chemotactic receptors. Grafting the pentapeptide to the C-terminus of the chemotactic receptor of the strong chemoattractant of PGPR chemoattractant to the rhizosphere can enhance its chemotactic response to the strong chemoattractant, thereby realizing the improvement of the rhizosphere chemotactic colonization ability of PGPR.

Technical scheme of the present invention is realized like this:

A method for improving PGPR rhizosphere chemotactic colonization ability, the steps are:

(1) Query the chemotactic receptor of the bacterium from the genome annotation of a certain PGPR, and then screen the domains in the chemotactic receptor that are related to enhancing the efficiency of methylation modification according to the amino acid sequence of the chemotactic receptor;

(2) Screening pentapeptides that may bind to methyltransferases involved in chemotaxis from the C-terminal extension of the domain in step (1);

(3) Carry out molecular modeling on the pentapeptides screened in step (2), perform homology modeling on the methyltransferases involved in chemotaxis, and screen the methyltransferases involved in chemotaxis according to the binding free energy of the two Pentapeptides with low binding free energy;

(4) Grafting the pentapeptide in step (3) to the C-terminus of the strong chemoattractant of PGPR chemoattractant rhizosphere and the chemoattractant receptor that does not contain the pentapeptide screened in step (3), to obtain chemotactic colonization Engineering bacteria with improved ability.

In the above step (1), the screening of domains related to enhanced methylation modification efficiency in chemotactic receptors is realized by smart online analysis tool.

The aforementioned structural domains related to enhancing the efficiency of methylation modification are referred to as MA domains.

Molecular modeling in the above step (3) uses chemoffice19.0_win software, and homology modeling uses SWISS-MODEL tool.

The above PGPR is Pseudomonas UW4, the methyltransferase involved in chemotaxis is CheR2, and its GenBank accession number is AFY21330.

The pentapeptide sequence in the above step (4) is shown in SEQ ID No.1, and the chemotactic receptor not containing pentapeptide is McpACC, and its sequence is shown in SEQ ID No.7.

Utilize the engineering bacterium of the pseudomonas UW4 prepared by the above-mentioned method, described engineering bacterium obtains by grafting the pentapeptide shown in SEQID No.1 to the C-terminus of pseudomonas UW4 chemotactic receptor Gene editing of Pseudomonas UW4.

The aforementioned Pseudomonas UW4 chemotactic receptor is a Pseudomonas UW4 chemotactic receptor that does not contain or has knocked out the pentapeptide that binds to CheR2.

The first construction method of the above-mentioned engineering bacteria, which uses the Pseudomonas UW4 chemotactic receptor that does not contain the pentapeptide combined with CheR2 as the target fragment, and grafts the screened pentapeptide sequence combined with CheR2 into the target fragment. The C-terminal of the fragment, the steps are: design the homologous fragment HRF1 sequence as shown in SEQ ID No.2, connect it with the plasmid pEX18Gm to obtain pEX18Gm-McpACC+PEKPR, and then transfer it into Escherichia coli competent, and then transform through parental hybridization Up to UW4, the successful identification is UW4-1 engineering bacteria.

The second construction method of the above-mentioned engineering bacteria, this method is based on the engineering bacteria constructed by the first method, and takes the chemotactic receptor containing the pentapeptide combined with CheR2 as the target fragment, and knocks out the target fragment. C-terminal pentapeptide, the steps are: design the homologous fragment HRF2 sequence as shown in SEQ ID No.3, connect it with the plasmid pEX18Gm to obtain pEX18Gm-Mcp14ΔPEKPR, and then transform it into UW4-1 engineering bacteria through parental hybridization, and the identification is successful. It is UW4-2 engineering bacteria.

The present invention has the following beneficial effects:

1. Our research group found that the C-terminal extension of at least one chemotactic receptor in bacteria contains a pentapeptide, which can mediate the interaction between methyltransferase and methylesterase. Chemotactic receptors can be reversibly methylated to enhance chemotactic response. Using the method idea of this application, the chemotactic receptors of various PGPR bacteria can be recombined, and finally engineering bacteria with strong rhizosphere chemotactic colonization ability can be obtained. The measures to improve the rhizosphere chemotaxis and colonization ability of PGPR are still relatively few. Our research group previously invented a method to improve the rhizosphere chemotactic colonization ability of PGPR by increasing the metabolic rate of PGPR to strong chemoattractants in root exudates, which is limited by the secretion of strong chemoattractants from plant roots. Compared with it, the present invention is not affected by the amount of root exudate secretion, and the effect of improving the rhizosphere chemotactic colonization ability of PGPR is more remarkable.

2. Pseudomonas sp. UW4 ( Pseudomonas sp. UW4) is a typical PGPR. Preliminary studies have found that the strong chemoattractant of this bacteria to rhizosphere is ACC, and the chemotactic receptor of ACC is McpACC (GenBank accession number is WP_015093116) , the methyltransferase involved in chemotaxis is CheR2 (GenBank accession number is AFY21330), and increasing its metabolic rate for ACC can increase its chemotactic colonization and growth-promoting effect in the wheat rhizosphere. The present invention introduces that on the basis of identifying the terminal pentapeptide of the UW4 chemotactic receptor, the pentapeptide is grafted to the end of McpACC to enhance the methylation modification efficiency of McpACC, thereby improving the chemotactic response of UW4 to ACC and improving its Chemotactic competitiveness and growth-promoting effects in the rhizosphere. Pot experiments showed that the amount of colonization in the wheat rhizosphere was 62.0% higher than that of the starting strain, the root length was 6.3% higher than that of the starting strain, the root dry weight was 10.3% higher than that of the starting strain, and the height of the shoot was 16.0% higher than that of the starting strain. The dry weight was 16.5% higher than that of the starting strain.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Figure 1 is the molecular docking diagram of CheR2 and the C-terminal pentapeptide PEKPR of Mcp14 in Pseudomonas UW4, in which (A) the structural overview of the docking complex between CheR2 and the pentapeptide PEKPR. Stick graphs represent pentapeptides. (B) Residues where CheR2 binds to the pentapeptide PEKPR. (C) Ligplot plot of CheR2 docking with pentapeptide. Hydrogen bonds are indicated by green dashed lines between the atoms involved, hydrophobic bonds are indicated by red arcs with spokes towards the ligand atoms they interact with. (D) Amino acid residues involved in pentapeptide binding in CheR2.

Figure 2 is the electrophoresis analysis of the PCR detection products of UW4-1 and UW4-2 strains; wherein 1. the primer pair is UW4-1-F1 and UW4-1-R1A, and the template is the UW4 genome; 2. the primer pair is UW4-1 -F2 and UW4-1-R2B, the template is the UW4 genome; 3. The primer pair is UW4-1-F1 and UW4-1-R1A, the template is the UW4-1 genome; 4. The primer pair is UW4-1-F2 and UW4 -1-R2, the template is UW4-1; 5. The primer pair is UW4-1-F1 and UW4-1-R1, the template is UW4-2; 6. The primer pair is UW4-1-F2 and UW4-1-R2 , the template is UW4-2.

Figure 3 is the colonization amount of Pseudomonas UW4 strain in the wheat rhizosphere and the growth-promoting effect on wheat; wherein A, the colonization amount of bacteria in the wheat rhizosphere; B, the root length of wheat; C, the dry weight of wheat root ; D, height of above-ground parts of wheat; E, dry weight of above-ground parts of wheat. Ctr, control; different lowercase letters indicate significant differences ( P <0.05).

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

A method for improving PGPR rhizosphere chemotactic colonization ability, the steps are:

(1) Query the chemotactic receptor of the bacterium from the genome annotation of a certain PGPR, and then screen the domains in the chemotactic receptor that are related to enhancing the efficiency of methylation modification according to the amino acid sequence of the chemotactic receptor;

(2) Screening pentapeptides that may bind to methyltransferases involved in chemotaxis from the C-terminal extension of the domain in step (1);

(3) Carry out molecular modeling on the pentapeptides screened in step (2), perform homology modeling on the methyltransferases involved in chemotaxis, and screen the methyltransferases involved in chemotaxis according to the binding free energy of the two Pentapeptides with low binding free energy;

(4) Grafting the pentapeptide in step (3) to the C-terminus of the chemotactic receptor of the strong chemoattractant in root exudates that do not contain the pentapeptide, to obtain an engineered bacterium with improved chemotactic colonization ability.

In the above step (1), the screening of domains related to enhanced methylation modification efficiency in chemotactic receptors is realized by smart online analysis tool.

The aforementioned structural domains related to enhancing the efficiency of methylation modification are referred to as MA domains.

Molecular modeling in the above step (3) uses chemoffice19.0_win software, and homology modeling uses SWISS-MODEL tool.

In most PGPR bacteria, at least one chemotactic receptor has a C-terminal pentapeptide that can bind to a methyltransferase involved in chemotaxis. Therefore, this method is applicable to most PGPRs.

Take Pseudomonas sp. UW4 ( Pseudomonas sp. UW4): the deposit of the American Agricultural Research Culture Collection Center (the deposit number is NRRL B-50193, and the deposit date is June 9, 2008) as an example to illustrate:

Example

Material

1.1 Experimental strains

Pseudomonas sp. UW4 ( Pseudomonas sp. UW4): preserved by the American Agricultural Research Culture Collection (the preservation number is NRRL B-50193, and the preservation date is June 9, 2008). The American Agricultural Research Service Culture Collection is located in Pecheria, Illinois. It is a government-owned culture collection supported by the Agricultural Research Center of the United States Department of Agriculture.

1.2 Medium

LB liquid medium: Weigh 5g of yeast extract, 10g of tryptone, and 10g of sodium chloride, dissolve in 1000mL of distilled water, dispense into 250ml Erlenmeyer flasks, and autoclave at 121°C for 30min.

Preparation of LB solid medium: Weigh 5g of yeast extract, 10g of tryptone, and 10g of sodium chloride, dissolve in 1000mL of distilled water, add 20g of agar powder to the solid medium, dispense it into a 250ml Erlenmeyer flask, and autoclave at 121°C for 30min.

Prediction of terminal pentapeptides of Pseudomonas UW4 chemotactic receptors

There are 28 chemotactic receptors annotated in the Pseudomonas UW4 genome, and the amino acid sequences of the 28 chemotactic receptors were analyzed using the smart online analysis tool (http://smart.embl-heidelberg.de/index2.cgi) The MA domain (Methyl-Accepting domain) present in the receptor, the C-terminal extension of this domain may contain a pentapeptide sequence that binds to CheR2. At the same time, the amino acid sequences of 28 kinds of receptors were aligned and analyzed using DNAMAN software to find chemotactic receptors with extended regions at the C-terminal of the receptors. There may be pentapeptide sequences in the extended regions of the C-terminals. It was found that the C-terminus of four receptors contains an extension region, among which Mcp11 has only four amino acids in the extension region and cannot form a pentapeptide sequence, so the remaining three receptors (Mcp14 (shown in sequence SEQ ID No.4), Mcp27 ( The sequence shown in SEQ ID No.5) and Mcp26 (shown in the sequence SEQ ID No.6)) are preliminarily predicted to contain a pentapeptide sequence that can bind to the CheR2 protein. The three predicted pentapeptide sequences are PEKPR, VVDKA and NQLTN, respectively (Table 1).

Table 1 Alignment results of C-terminal sequences of Pseudomonas UW4 chemotactic receptors

^a Underlined characters represent putative pentapeptides bound to CheR and CheB.

3. Docking of quasi-pentapeptide molecules and CheR2 molecules

Use chemoffice19.0_win software to model the pseudopentapeptide molecular structure, and use the online modeling and analysis tool SWISS-MODEL (https://swissmodel.expasy.org/) to model the CheR2 homology. The template number used is SMTLID: 5y4r.1. Among the three pentapeptides, only PEKPR can bind to the β-subdomain of CheR2. The amino acid residues that bind to the pentapeptide in CheR2 are Leu173, Gln174, Pro179, Lys180, Gly181, Pro182, and Trp185 (Figure 1A, B). The forces are mainly hydrogen bonds, hydrophobic bonds and van der Waals forces (Fig. 1C, D), and the binding free energy is -13.17 kcal/mol. The other two pentapeptides cannot bind to the β-subdomain of CheR2, indicating that the pentapeptide PEKPR may be the pentapeptide that mediates the binding of CheR and CheB.

Construction of Pseudomonas UW4 ACC Chemotactic Receptor Grafting Pentapeptide Engineering Bacteria

In order to improve the chemotactic response of Pseudomonas UW4 to ACC, two engineering bacteria were constructed. One was to graft the pentapeptide PEKPR to the C-terminal of the ACC chemotactic receptor McpACC, named UW4-1; the other was to graft UW4 Pentapeptide PEKPR truncated of Mcp14 at -1, designated UW4-2. The construction method is that two homologous recombination fragments HRF1 and HRF2 were synthesized by Huada Gene Company. The HRF1 fragment (sequence shown in SEQ ID No.2) contains 206 bp of upstream homology arm, 221 bp of downstream homology arm, restriction enzyme EcoRI, KpnI restriction site and pentapeptide PEKPR base sequence CCGGAAAAACCGCGC. HRF1 was ligated with plasmid pEX18Gm to obtain pEX18Gm-McpACC+PEKPR. The constructed plasmid was transformed into Escherichia coli S17-1 by conventional heat shock method, and transformed into UW4 by parental hybridization. Colony PCR identification was performed using primer pairs UW4-1-F1 and UW4-1-R1, UW4-1-F2 and UW4-1-R2 (Table 2) to obtain UW4-1 (Figure 2). Use HRF2 homologous recombination to knock out the pentapeptide of Mcp14 of UW4-1, HRF2 (sequence shown in SEQ ID No.3) contains upstream homology arm 206 bp, downstream homology arm 206 bp, restriction enzymes EcoRI and KpnI restriction sites . HRF2 was ligated with plasmid pEX18Gm, resulting in pEX18Gm-Mcp14ΔPEKPR. The plasmid was transformed into Escherichia coli S17-1 by conventional heat shock method, and then transformed into UW4-1 by parental hybridization to generate UW4-2. Colony PCR was performed using primer pairs UW4-1-F1 and UW4-1-R1, UW4-1-F2 and UW1-1-R2 (Table 2) to identify UW4-2 (Figure 2).

Table 2 Primer list

4.1 Double-parent hybridization method

(1) Inoculate 10 μL of Escherichia coli S17-1 strains containing plasmids pEX18Gm-McpACC+PEKPR and pEX18Gm-Mcp14ΔPEKPR respectively into 10 ml liquid LB medium, and place them in a shaker at 37°C at 220 rpm for 12-15 hours;

(2) Inoculate Pseudomonas UW4 stored in a 10 μL glycerol tube into 10 ml liquid LB medium, place on a shaker at 30°C, and culture at 220 rpm for 12-15 hours;

(3) Collect 1.5 mL of the two S17-1 bacterial solutions after the cultivation and centrifuge them in centrifuge tubes, and discard the supernatant after centrifuging at 12000 rpm for 1 min;

(4) Resuspend the two kinds of S17-1 bacteria in 1ml 0.85% NaCl solution, centrifuge at 12000 rpm for 1min, discard the supernatant, and add 1.5mL UW4 to the centrifuge tubes containing the two kinds of S17-1 bacteria respectively Bacterial solution, after centrifugation at 12000 rpm, discard the supernatant;

(5) Resuspend the bacteria with 1ml 0.85% NaCl solution, centrifuge at 12000 rpm and discard the supernatant, repeat this step 5-6 times;

(6) Resuspend the bacteria with 100 μL 0.85% NaCl solution;

(7) Cut the nitrocellulose membrane to the size of the petri dish, and spread it on the LB solid plate;

(8) The above-mentioned two kinds of resuspended bacterial solutions were respectively added dropwise on a flat plate covered with nitrocellulose membrane, and incubated at a constant temperature of 30° C. for 24 hours;

(9) Rinse the cells from the nitrocellulose membrane with 800 μL of 0.85% NaCl solution after the cultivation;

(10) After resuspending the bacterial solution, draw 100 μL and spread it on the LB solid plate containing gentamicin 25 μg/mL and ampicillin 100 μg/mL, and place it at 30°C for constant temperature and static culture for 12-16 hours to make Pseudomonas UW4 or UW4-1 with a single exchange;

(11) Pick a single exchange subculture in liquid LB medium at 30°C and 220 rpm for 5 hours, then spread 10% sucrose on a solid LB plate containing 100 μg/mL ampicillin, and culture at a constant temperature of 30°C for 24- 35 hours.

The colonies that can grow are double crossovers, and the double crossovers obtained from two Escherichia coli S17-1 containing different plasmids are UW4-1 strain and UW4-2 strain, respectively.

4.2 Colony PCR identification of strains UW4-1 and UW4-2

The primers used in PCR are listed in Table 2.

The reaction system and reaction procedure are as follows:

The result is shown in Figure 2.

Pot experiment of Pseudomonas UW4 ACC chemotactic receptor grafted pentapeptide engineering bacteria

Wheat seeds were soaked in 70% alcohol for 1 min, then rinsed with sterile water for 3 times, soaked in 2% sodium hypochlorite for 5 min, rinsed with sterile water for ₅ times, and soaked in 0.1% HgCl for 5 min, rinsed with sterile water for 6 times. Soak the sterilized wheat seeds in UW4, UW4-1 and UW4-2 bacterial suspensions with OD600=1, and imbibition treatment in the dark for 24 hours, while the control soaked in sterile water. Potted after germination.

The soil is prepared by mixing peat soil and vermiculite at a ratio of 1:1, pouring enough water, and then sterilizing at 121°C for 3 hours. The obtained soil was divided into polyethylene seedling trays, and the treated seeds were sown into potted plants, 3 seeds per hole, about 1 cm deep. After sowing, they were cultured at 25°C, under the conditions of 16 hours of light and 8 hours of darkness. Two days ago, the plants were watered with 5 mL of different bacterial suspensions with OD600=1, and 5 mL of sterile water was used as a control. After the wheat grew for about 15 days, the roots were taken for tissue grinding, and then gradiently diluted and coated with ampicillin-resistant 100 μg/mL The LB solid plate counted the number of colonized bacteria in the rhizosphere of potted wheat (Fig. 3A). The root and above-ground part were cut off to measure the length of root and above-ground part respectively. After the roots and aerial parts were dried to constant weight, the dry weight of roots and aerial parts were measured respectively (Figure 3BCDE).

It can be seen from Figure 3 that when wheat was inoculated with Pseudomonas UW4, UW4-1 and UW4-2, compared with UW4-2 and UW4, the colonization of UW4-1 in the wheat rhizosphere increased by 14.3% and 62.0%, respectively. The colonization of UW4-2 was 41.8% higher than that of UW4 (Fig. 3A). The root length of wheat inoculated with UW4, UW4-1 and UW4-2 increased by 32.3%-40.7% compared with the uninoculated control. Wheat inoculated with UW4-1 increased root length by 4.3% and 6.3%, respectively, compared with wheat inoculated with UW4-2 and UW4, and there was no difference in root length between inoculated UW4-2 and UW4 (Fig. 3B). Inoculated with UW4, UW4-1 and UW4-2, the dry weight of wheat roots increased by 64.8% to 81.8% compared with the control. The root dry weight of wheat inoculated with UW4-1 increased by 5.5% and 10.3% compared with those inoculated with UW4-2 and UW4, respectively, and the wheat inoculated with UW4-2 increased by 4.5% compared with that inoculated with UW4 (Fig. 3C). Compared with the control, the height of aerial parts of wheat inoculated with UW4, UW4-1 and UW4-2 increased by 14.9%-33.2%. The height of the aerial part of wheat inoculated with UW4-1 was 5.1% and 16.0% higher than that of wheat inoculated with UW4-2 and UW4, respectively, and the height of the aerial part of wheat inoculated with UW4-2 was increased by 10.3% compared with that inoculated with UW4 (Fig. 3D). The dry weight of above-ground parts of wheat inoculated with UW4, UW4-1 and UW4-2 increased by 26.7%-47.6% compared with the control. The above-ground dry weight of wheat inoculated with UW4-1 was 13.2% and 16.5% higher than that of wheat inoculated with UW4-2 and UW4, respectively, and the dry weight of above-ground parts of wheat inoculated with UW4-2 was increased by 2.9% compared with that inoculated with UW4 (Fig. 3E).

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (10)

1. a method for improving PGPR rhizosphere chemotactic colonization ability, is characterized in that, step is: (1) Query the chemotactic receptor of the bacterium from the genome annotation of a certain PGPR, and then screen the domains in the chemotactic receptor that are related to enhancing the efficiency of methylation modification according to the amino acid sequence of the chemotactic receptor; (2) Screening pentapeptides that may bind to methyltransferases involved in chemotaxis from the C-terminal extension of the domain in step (1); (3) Carry out molecular modeling on the pentapeptides screened in step (2), perform homology modeling on the methyltransferases involved in chemotaxis, and screen the methyltransferases involved in chemotaxis according to the binding free energy of the two Pentapeptides with low binding free energy; (4) Grafting the pentapeptide in step (3) to the C-terminus of the strong chemoattractant of PGPR rhizosphere, which does not contain the pentapeptide screened in step (3), to obtain chemotactic colonization Engineering bacteria with improved ability. 2. The method for improving the chemotactic colonization ability of PGPR rhizosphere according to claim 1, characterized in that: in the step (1), the structural domains related to enhancing methylation modification efficiency in screening chemotactic receptors are Realized by smart online analysis tool. 3. The method for improving PGPR rhizosphere chemotaxis and colonization ability according to claim 2, characterized in that: the structural domain related to enhancing methylation modification efficiency refers to the MA structural domain. 4. The method for improving PGPR rhizosphere chemotactic colonization ability according to claim 3, characterized in that: molecular modeling in the step (3) uses chemoffice19.0_win software, and homology modeling uses SWISS- MODEL tools. 5. according to the method for improving PGPR rhizosphere chemotactic colonization ability described in any one of claim 1-3, it is characterized in that: described PGPR is Pseudomonas UW4, and the methyltransferase that participates in chemotaxis is CheR2 , whose GenBank accession number is AFY21330. 6. the method for improving PGPR rhizosphere chemotactic colonization ability according to claim 5, is characterized in that: in described step (4), pentapeptide sequence is as shown in SEQ ID No.1, does not contain the pentapeptide The receptor is McpACC, and its sequence is shown in SEQ ID No.7. 7. Utilize the engineering bacterium prepared by the method described in any one of claim 1-4,6, it is characterized in that: described engineering bacterium is by grafting the pentapeptide shown in SEQ ID No.1 to Pseudomonas Gene-edited Pseudomonas UW4 obtained from the C-terminus of the UW4 chemotactic receptor. 8. The engineering bacterium according to claim 7, characterized in that: the Pseudomonas UW4 chemotactic receptor is a Pseudomonas UW4 chemotactic receptor that does not contain or has knocked out the pentapeptide combined with CheR2 . 9. The construction method of the engineering bacterium described in claim 8, is characterized in that, the step is: design homologous fragment HRF1 sequence as shown in SEQ ID No.2, connect with plasmid pEX18Gm to obtain pEX18Gm-McpACC+PEKPR, then first transfer into Escherichia coli competent, and then transformed into UW4 through parental hybridization, and the successful identification is UW4-1 engineering bacteria. 10. The construction method of the engineering bacterium described in claim 9, is characterized in that, the step is: design homologous fragment HRF2 sequence as shown in SEQ ID No.3, connect with plasmid pEX18Gm, obtain pEX18Gm-Mcp14ΔPEKPR, pass parental again Hybrid transformation into the UW4-1 engineering bacterium constructed in claim 9, the successful identification is the UW4-2 engineering bacterium.

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