| Rice bacterial leaf streak is caused by Xanthomonas oryzae pathovar oryzicola(here after Xoc),which is one of the important bacterial diseases resulting severe losses in rice production and constrainting the production of staple crop regions in Asia and parts of Africa.The pathogenicity of pathogens in most plants mainly use III effectors,extracellular protease,extracellular polysaccharides and other pathogenic factors.Meanwhile,the bacteria use two-component regulatory system feel and respond outside stimuli,Now its role in pathogenicity as well as antibiotic resistance is becoming the focus of attention.Because of the structure characteristics of sensor gene that make it easier to sensing environmental stimuli and transducing signal to the corresponding regulators which regulate downstream gene transcription,so they play important roles in two-component systems.Genome annotation indicates that 47 sensor genes and 52 regulator genes in two-component regulatory system of Xoc GX01.In this study mutated 25 of sensor genes by using pK 18mob a single exchange of homologous way,constructing 22 integration mutants.These mutants were tested in the extracellular protease,the extracellular polysaccharide and the motility,Results showed that the extracellular protease of mutants of 9 genes markedly decreased compared with Xoc GX01,including XOC1172,XOC1020,XOC0606,XOC3259,XOC1980,XOC4053,XOC0294,XOC0707,XOC0269;the extracellular polysaccharide of mutants of 8 genes markedly decreased compared with Xoc GX01,including XOC1172,XOC4052,XOC0606,XOC3259,XOC1980,XOC1178,XOC0294,XOC0269;the mobility of mutants of 10 genes markedly decreased compared with Xoc GX01,including XOC1172,XOC1178,XOC0606,XOC0707,XOC0294,XOC3897,XOC1980,XOC4018,XOC0665,XOC2440,Then all mutants were tested in virulence,However,only the data of the 16 mutants is feasible,it showed the decrease of the mutants of 13 genes is obvious.Finally,it ’was found that the extracellular protease,the extracellular polysaccharide,the motility and the virulence of XOC0606,XOC0294,XOC1980,XOC1172 and XOC1020 markedly decreased compared with Xoc GX01.In support of these genes is virulence-related genes,we made the functional complementary with them,Unfortunately,the mutants of XOC0606,XOC 1172,XOC0294 can be restore the wild-type level in the virulence except some phenotypes,only the mutants of XOC1980 and XOC1020 can be restored the wild-type level in the virulence and phenotypes,Further research of them has showned that:the mutation of XOC1980 make the exopolysaccharides,extracellular protease,motility and virulence decreased,but not related to HR,cell reproduction,the generation of biofilm;the mutation of XOC1020 make the extracellular protease,virulence decreased,but not related to motility,exopolysaccharides,HR,cell reproduction,the generation of biofilm. |
