The Rcs phosphorelay modulates the expression of plant cell wall degrading enzymes and virulence in Pectobacterium carotovorum ssp. carotovorum

Production of plant cell wall degrading enzymes, the major virulence factors of soft-rot Pectobacterium species, is controlled by many regulatory factors. Pectobacterium carotovorum ssp. carotovorum SCC3193 encodes an Rcs phosphorelay system that involves two sensor kinases, RcsC Pcc and RcsD Pcc , and a response regulator RcsB Pcc as key components of this system, and an additional small lipoprotein RcsF Pcc . This study indicates that inactivation of rcsC Pcc , rcsD Pcc and rcsB Pcc enhances production of virulence factors with the highest effect detected for rcsB Pcc . Interestingly, mutation of rcsF Pcc has no effect on virulence factors synthesis. These results suggest that in SCC3193 a parallel phosphorylation mechanism may activate the RcsB Pcc response regulator, which acts as a repressor suppressing the plant cell wall degrading enzyme production. Enhanced production of virulence factors in Rcs mutants is more pronounced when bacteria are growing in the absence of plant signal components.