BioProject

Posttranscriptional regulator RsmA is part of a regulatory system that controls production of plant cell wall degrading enzymes (PCWDEs), motility and other virulence factors among the Pectobacterium spp of plant pathogens. More...

Posttranscriptional regulator RsmA is part of a regulatory system that controls production of plant cell wall degrading enzymes (PCWDEs), motility and other virulence factors among the Pectobacterium spp of plant pathogens. We constructed the knockout mutation of rsmA gene in Pectobacterium wasabiae strain SCC3193. The rsmA- strain has three times lower growth rate but increased virulence when compared to wild type. To explain this phenotype we compared wild type and rsmA- mRNA levels using genome wide microarray. We found that the synthesis of all known virulence factors and flagella is upregulated, while cell division and peptidoglycan synthesis is down regulated in rsmA- strain. The TCA cycle is directed fully to energy production, indicating low energetic status of the cell that is a probable reason for the low growth rate of the mutant. Growth experiments showed that the enzymatic activities of extracellular virulence factors polygalacturonase and pectate lyase are very high throughout the growth curve even without induction by plant component. Wild type cells are rod shaped in liquid media, but elongated and hyperflagellated in swarm plate containing potato tuber extract and in potato tuber. The rsmA- strain exhibits the same conditional phenotype, but differentiation into swarmer cells is faster and cell elongation more pronounced. Virulence experiments in potato tuber showed that although rsmA- strain causes bigger tissue maceration, its ability to compete with the natural bacterial community in the host is decreased. We conclude that the lack of RsmA switches the cells to infective phenotype characterized by expression of virulence factors and swarming. The lack of control over these energy costly processes is probably the reason for decreased growth rate and fitness. Overall design: Gene expression analysis from P. wasabie SCC3193 wildtype and SCC3193 rsmA mutant was performed on RNA samples extraxcted from the rsmA mutant (at 40 and 48 hours) and wildtype (at 24 hours). The strain were grown on 1.5% agar M9 minimal media plates supplemented with 10% potato extract. Three biological replicates were used from each strain at each time point. Less...