A two-component sensor kinase (GacS) mediated signal transduction pathway involved in production of antifungal compounds in Pseudomonas chlororaphis O6.

E. intermedium Blocontrol activity of a P. chlororaphis rhizobacteium O6, depends to the synthesis of extracellular secondary metabolites and exoenzymes, thought to antagonize the pathogenicity of a variety of phytopathogenic fungi. The production of secondary metabolites and exoenzymes in O6, depends essentially on the GacS-mediated signal transduction pathway, which activates largely unknown signal transduction pathway. To exploit the GacS-mediated signal transdcution pathway involved in activation of ph genes that are necessary for biosynthesis of phenazine from P. chlororaphis O6, we cloned and sequenced the phz operon, rpoS gene encoding stationary specific sigma factor, ppx gene encoding polyphosphatase, and lon gene encoding ion protease. Expression of each gene in wild type and GacS mutant were analyzed by RT-PCR. Transcripts from rpoS, phzI enconing acylhomoserine lactone (AHL) synthase, and ph structural genes in the GacS mutant were reduced in each of these growth phases compared to the wild type. The GacS or Lon mutant was found to be deficient in the production of phenzines, exoenzymes, and the acylhomoserine lactone. These mutants were not complemented by ph operon and addition of exogenous AHL. These results indicate that the GacS global regulatory systems controls phenazine production at multiple levels. Future research will focus to identifying the GacS-mediated regulatory cascade involving in production of phenazine in P. chlororaphis.