Function analysis of LC_Clp transcription factor in Lysobacter capsici X2-3

Abstract:

Lysobacter capsici X2-3, a plant growth promoting rhizobacteria (PGPR) strain isolated from the wheat rhizosphere, shows strong antimicrobial activity against many plant pathogenic fungi and oomycetes. However, little is known about the antibiotics produced by X2-3 as well as their regulation mechanism. [Objective] Our study aimed to clarify the regulation effect of LC_Clp transcription factor on the antibiotic production of L. capsici X2-3 and to provide reference for deep understanding of its biocontrol mechanism. [Methods] We selected a LC_clp mutant M356 from the mutant bank that was generated by the random insertion of the EZ-Tn5 transposon and certified by plasmid rescue. Additionally, we analyzed the differences of LC_clp gene in antimicrobial activity, secretion of extracellular enzymes, and regulation of gene expression among X2-3, mutant M356 and the complementary strain MCS28. [Results] Antimicrobial activity of mutant M356 against pathogenic fungi and oomycetes was completely lost as compared with that of X2-3 and the antibiotics produced by M356 was undetected by HPLC method. Extracellular enzymes such as protease, cellulose and chitinase that was secreted by mutant M356 decreased significantly. Expression of genes relating transcriptional regulators, secondary metabolism and extracellular enzymes were lowered dramatically in M356 as compared with that of wild-type strain X2-3. However, all the items tested in complementary strain MCS28 were similar with those of wild-type strain X2-3. [Conclusion] As a global regulator, LC_Clp regulates the synthesis of antibiotics, the production of extracellular enzymes and the expression of multiple genes in L. capsici X2-3.