SYNTHESIS AND SECRETION OF ERWINIA-CHRYSANTHEMI VIRULENCE FACTORS ARE COREGULATED

Regulation of the transcription of four operons (outS, outB, outT, outC-M) coding for components of the protein secretion apparatus of Erwinia chrysanthemi has been studied. Regulation of the outC operon expression by kdgR, which is the repressor of all the genes involved in pectinolysis, requires the outT gene product, suggesting that OutT could be a transcriptional activator of outC. The gene pecS which regulates pel and celZ gene expression, also negatively controls the outC operon in a manner independent of the regulation by OutT. All environmental conditions that affect pectate lyase production also modulate Out protein synthesis. Thus, pectate lyase synthesis and secretion are very tightly coregulated.