The PhoPQ two-component system is the major regulator of cell surface properties, stress responses and plant-derived substrate utilisation during development of Pectobacterium versatile-host plant pathosystem

Abstract

The PhoPQ two-component system, originally described in pectobacteria as PehRS, was previously shown to regulate a single gene, pehA. Using an insertional phoP mutant of Pectobacterium versatile, we demonstrate that PhoP controls a regulon of at least 116 genes with a large fraction of regulon members specific for pectobacteria. The functions performed by the PhoP controlled genes include transport and metabolism of plant-derived carbon sources (polygalacturonate, arabinose and citrate), modification of bacterial cell envelope and stress resistance. High concentrations of calcium and magnesium ions were found to abolish the PhoPQ-dependent transcription activation. Reduced PhoP expression and minimisation of PhoP dependence of regulon members expression in the cells isolated from rotten potato tuber tissues suggest that PhoPQ system may adjust expression levels of multiple virulence-related genes during the course of P. versatile-host plant pathosystem development.