A two-component system in Ralstonia (Pseudomonas) solanacearum modulates production of PhcA-regulated virulence factors in response to 3- hydroxypalmitic acid methyl ester

摘要: Expression of virulence factors in Ralstonia solanacearum is controlled by a complex regulatory network, at the center which PhcA, LysR family transcriptional regulator. We report here that expression phcA and production PhcA-regulated are affected products putative operon phcBSR(Q). phcB required for an extracellular factor (EF), tentatively identified as fatty acid derivative 3-hydroxypalmitic methyl ester (3-OH PAME), but biochemical function PhcB could not be deduced from DNA sequence analysis. The other genes predicted to encode proteins homologous members two-component signal transduction systems: PhcS has amino similarity histidine kinase sensors, whereas PhcR OrfQ similar response regulators. quite unusual because its output domain strongly resembles sensor protein. Production exopolysaccharide I, endoglucanase, pectin esterase was reduced 10- 100-fold only mutants with nonpolar insertion [which express phcSR(Q) absence EF]; simultaneously, fivefold. Both wild-type phenotype were restored addition 3-OH PAME growing cultures. Mutants polar insertions or lacking entire phcBSR(Q) region produced levels factors. genetic data suggest together regulate phcA, mechanism this unclear. At low EF, it likely phosphorylates PhcR, then interacts either PhcA (which full phcA) unknown component cascade inhibit phcA. When EF reaches threshold concentration, we reduces ability phosphorylate resulting increased