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FEMS Microbiol Lett. 2014 Sep;358(1):81-90. doi: 10.1111/1574-6968.12529. Epub 2014 Aug 12.

RavA/RavR two-component system regulates Xanthomonas campestris pathogenesis and c-di-GMP turnover.

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  • 1State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China; CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.


The two-component system (TCS), consisting of a response regulator (RR) and a cognate histidine kinase (HK), responds to extra-/intercellular cues and triggers adaptive changes. The RR, RavR, has been reported to act as a positive virulence regulator and a c-di-GMP hydrolase in Xanthomonas campestris pv. campestris (Xcc). Here, we identified the cognate HK, RavA, that regulate RavR phosphorylation levels and bacterial pathogenesis. Deletion of ravA, a putative HK gene flanking ravR, dramatically attenuated Xcc virulence. Phenotypes of the double mutant ΔravR/ΔravA were similar to those of ΔravR, suggesting that RavR is a downstream component of RavA signaling. RavA interacts with RavR and positively influences the phosphorylated RavR levels. In vitro analysis suggests that RavR is a bifunctional enzyme involved in c-di-GMP synthesis and degradation. Importantly, mutation and enzyme activity assays indicate that the phosphorylation level affects RavR c-di-GMP turnover activity. These results show that RavA acts as the RavR cognate HK, which fine-tunes RavR functions and enables bacteria to adapt quickly to intracellular changes.

© 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.


C-di-GMP turnover; RavA; RavR; phosphorylation; two-component system

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