Chemotactic rhizocompetence is strengthened by efficient adaptational methylation modification of the 1-aminocyclopropane-1-carboxylic acid chemoreceptor in Pseudomonas sp. UW4.

Background and Aims: Intensifying chemotactic rhizocompetence is an effective approach to improving PGPR colonization in the plant rhizosphere and promoting plant growth. Whether increasing the efficient adaptational methylation modification of chemoreceptors enhances chemotactic rhizocompetence is unknown. Pseudomonas sp. UW4 is a typical PGPR, and 1-aminocyclopropane-1-carboxylic acid (ACC) is the strong chemoattractant that directs it to the rhizosphere. Methods: The chemoreceptor pentapeptide involved in UW4 chemotaxis were identified through molecular docking and methylation reactions in vitro. The pentapeptide was identified as PEKPR residing in the C-terminus of the chemoreceptor Mcp14 and shows no sequence conservation with that of other bacteria. Two chemoreceptor mutants were constructed: in one, the pentapeptide was additionally grafted to the ACC chemoreceptor McpACC (UW4-1); in the other, the pentapeptide was transferred to McpACC (UW4-2). Results: UW4-1 and UW4-2 showed unchanged chemotactic responses to arginine and succinic acid compared to UW4, whereas the chemotactic responses of UW4-1 to ACC were 36.0% and 17.2% higher than those of UW4 and UW4-2, respectively. Wheat rhizosphere colonization by UW4-1 in nonaxenic pot trials was 62.0% and 14.3% higher than rhizosphere colonization by UW4 and UW4-2, respectively, and the root and shoot dry weights of wheat inoculated with UW4-1 were 10.3% and 5.5% and 16.5% and 13.2% higher, respectively, than those of wheat inoculated with UW4 and UW4-2. Conclusion: Grafting the pentapeptide to the chemoreceptor corresponding to the strong rhizosphere chemoattractant for PGPR increases PGPR chemotactic response to the strong rhizosphere chemoattractant, increases plant rhizosphere colonization, and leads to higher plant growth promotion. [ABSTRACT FROM AUTHOR]