EPSR MODULATES PRODUCTION OF EXTRACELLULAR POLYSACCHARIDES IN THE BACTERIAL WILT PATHOGEN RALSTONIA (PSEUDOMONAS) SOLANACEARUM

Ralstonia solanacearum is the causal agent of bacterial wilt of many a griculturally important crops, Exopolysaccharide synthesized by produc ts of the epsI operon is the major virulence factor for R. solanacearu m. Expression of epsI has been demonstrated to be under the control of several proteins, including several two-component regulators, Overexp ression of EpsR was found previously to reduce the amount of synthesis specifically from the epsl promoter, Here we present data that a sing le chromosomal copy of epsR activates the epsl promoter, suggesting th at EpsR is a concentration-dependent effector of epsl gene expression, Furthermore, the ability of EpsR to modulate epsl expression is depen dent on the phosphorylation state of EpsR, Gel mobility shift assays s uggest that EpsR can specifically bind the epsI promoter and that this binding requires a phosphorylated form of EpsR.