Comparative analysis of the RcsC sensor kinase from Erwinia amylovora and other enterobacteria

We have previously demonstrated that, though the Erwinia amylovora rcsC mutant produces more amylovoran than the Ea1189 wild type (WT) strain in vitro, it is avirulent on host plants. In this study, we further characterized the RcsC and its homologs from various enterobacteria. Complementation studies showed that RcsC homologs from Pantoea stewartii, Salmonella enterica and Yersinia pestis, but not that from E. coli, partially restored virulence of the Erwinia rcsC mutant on 'Gala' apple shoots. However, all RcsC homologs could not rescue amylovoran production phenotype of the Erwinia rcsC mutant in vitro. In addition, a chimeric construct containing the sensor domain of Erwinia RcsC and the output domain of E. coli RcsC restored virulence of the Erwinia rcsC mutant, but not amylovoran production; whereas a chimeric construct containing the sensor domain of E. coli RcsC and the output domain of Erwinia RcsC rescued amylovoran production phenotype of the Erwinia rcsC mutant, but not virulence. These results suggest that the sensor domain of RcsC might be important for regulating bacterial virulence, whereas the output domain of RcsC might be responsible for amylovoran production in vitro.