Function Identification Of Two-Component Regulatory System Colrs Gene In Xanthomonas Oryzae PV. Oryzicola

Two-component regulatory system systems (TCSs) is the most important signal transduction system which sense extracellular signals of microorganisms and it is consist of sensor protein and response regulator. The sensor proteins sense extracellular environment changes and deliver the change signals into intracellular response regulator proteins (RRs). The activated regulator proteins regulated the transcription of downstream genes, finally make adaptation reaction of microorganisms. Earlier researchs showed that a TCS colRS, which comprises a HK ColS and a RR ColR, involved in the capacity of bacteria to colonize in plant roots. Later studies suggest that colRS seriously affect pathogenicity, the stability and functions of membrane, stress resistances and so on.Xanthomonas oryzae pathovar oryzicola(Xoc) is the pathogen of bacterial leaf streak of rice. It could be spreaded by wind or rain, and infects, through the stomata and wound, mutiplies and expands in mesophyll of rice leaf, then cause serious disease. Three pairs of colRS homologous genes were predicted in Xoc GX01strains, including of XOC0817/XOC0818, XOC1171/XOC1172and XOC3259/XOC3260. In order to identify the functoins of those putative colRS genes, single deletion mutants, double deletion mutants and multiple deletion mutants were constructed by using homologous double exchange method. The mutants include six single deletion mutants:DM0817, DM0818, DM1171, DM1172, DM3259and DM3260, and eight double deletion mutants, DM0817/18, DM1171/72, DM0818/72, DM3259/18, DM3259/72, DM0817/71, DM3260/17and DM3260/71, and two tri-mutant:DMTCOLS (XOC0818, XOC1172and XOC3259are deleted) and DMTCOLR (XOC0817, XOC1171and XOC3260are deleted), and a tetra-mutant DMDG (XOC0817/XOC0818and XOC1171/XOC1172are deleted). Plant test and phenotype assays show that DM0817, DM0818, and DM0817/18decrease in EPS production and adaptation to phenol and osmotic stress.There is no any change for DM1171, DM1172and DM1171/72. For the DM3259and DM3260, the virulence, bio film formation, and heavy metals, organic solvents, and osmotic stress resistance were significantly decreased, extracellular polysaccharide increased, but its extracellular protease and motility no significant changes compared with the wild type strain. The result show that DM3259and DM3260significantly reduce capacity of colonization on rice leaves and restrain bacteria growth. Complementation strain CDM3259and CDM3260can restore the phenotypes to wild-type level.Above all, the coding products of XOC3259/XOC3260composition ColRS system in Xoc and this system control several important phenotypes and impact bacterial pathogenicity through regulatory a extremely complicated network. This study on ColRS systems will help us understand the pathogenic network of Xoc, and provides the basis to develope new methods and ways to control this important plant pathogenic bacteria.