The Yersinia pseudotuberculosisCpx envelope stress system contributes to transcriptional activation of rovM

ABSTRACTThe Gram-negative enteropathogen Yersinia pseudotuberculosispossesses a number of regulatory systems that detect cell envelope damage caused by noxious extracytoplasmic stresses. The CpxA sensor kinase and CpxR response regulator two-component regulatory system is one such pathway. Active Cpx signalling upregulates various factors designed to repair and restore cell envelope integrity. Concomitantly, this pathway also down-regulates key determinants of virulence. In Yersinia, cpxAdeletion accumulates high levels of phosphorylated CpxR (CpxR~P). Accumulated CpxR~P directly repressed rovAexpression and this limited expression of virulence-associated processes. A second transcriptional regulator, RovM, also negatively regulates rovAexpression in response to nutrient stress. Hence, this study aimed to determine if CpxR~P can influence rovAexpression through control of RovM levels. We determined that the active CpxR~P isoform bound to the promoter of rovMand directly induced its expression, which naturally associated with a concurrent reduction in rovAexpression. Site-directed mutagenesis of the CpxR~P binding sequence in the rovMpromoter region desensitised rovMexpression to CpxR~P. These data suggest that accumulated CpxR~P inversely manipulates the levels of two global transcriptional regulators, RovA and RovM, and this would be expected to have considerable influence on Yersiniapathophysiology and metabolism.