Phenazine regulated genes in Pseudomonas chlororaphis 30-84
Pseudomonas chlororaphis strain 30-84 is an effective biological control agent against take-all disease of wheat. Phenazines, bacterial secondary metabolites produced by 30-84, are essential for 30-84 to inhibit fungal pathogens, form biofilms, and effectively colonize the rhizosphere. However, how the bacteria themselves respond to phenazines remains unknown. In this study, we conducted an RNA-seq analysis by comparing the wild type strain with a phenazine deficient mutant. RNA-seq analysis identified over 200 genes differentially regulated by phenazines. Consistent with previous findings in Pseudomonas aeruginosa PAO1, phenazines positively contribute to the expression of their own biosynthetic genes. Moreover, phenazine regulatory genes including the phzI/phzR quorum sensing system and the rpeB response regulatory were also expressed at high levels in the presence of phenazines. Besides phenazine biosynthesis and regulatory genes, genes involved in secondary metabolism, exopoysaccharide production and iron uptake as well as amino acid transport were identified as the major components under phenazine control, including many novel genes. We have also demonstrated that mutation of the primary siderophore gene pvdA resulted in up-regulation of phenazine genes when grown in iron-limiting media. These findings implicate phenazines as signaling molecules to regulate gene expression and hence alter metabolism in P. chlororaphis strain 30-84. Overall design: A total of 4 samples were analyzed in AB medium + 2% casamino acids, Pseudomonas chlororaphis wild type strain (2 replicates);  Pseudomonas chlororaphis ZN mutant (2 replicates).