Cloning And Fuctional Study Of Clp Gene Of Xanthomonas Oryzae

Xanthomonas oryzae pv. oryzicola (Xooc) and Xanthomonas oryzae pv. oryzae (Xoo) cause leaf streak and leaf blight on rice, respectively. In this study, we identified and characterized the contribution of clp gene to motility, chemotaxis, extracellular polysaccharide (EPS) and virulence of the phytopathogens X. oryzae pv. oryzae strain PXO99 and X. oryzae pv. oryzicola strain Rs105.(I) A clp homologue, designated clprs, was cloned from X. oryzae pv. oryzicola, with degenerated primers by polymerase amplification reaction (PCR). A clp deletion mutant of strain Rs105 was constructed, and confirmed by PCR. Compared to the wild-type strain Rs105, the mutation of clp did not affecte growth, the clp mutant could yet elicit hypersensitive response (HR) on nonhost plants tobacco. Interestingly, the clp mutant do not lacked detectable flagella, but highly impaired in motility. Furthermore, the clp mutant displayed almost no chemotaxis toward glucose under aerobic conditions. Remarkably, it was observed that the clp mutant exhibited reductive production of extracellular polysaccharide (EPS) and significant reduction of virulence on adult rice plants compared to the wildtype strain. Our findings indicated that the clp gene played an important role in virulence on rice.(II) A clp homologue, designated clpxoo, was cloned from Xanthomonas oryzae pv. oryzae strain PXO99, with degenerated primers by PCR. Sequence comparison revealed that the gene in Xanthomonas is relatively conservative. A clp deletion mutant of strain PXO99 was constructed, and confirmed by PCR. Compared to the wild type, motility and chemotaxis of the clp gene mutant was decreased, and the deposit in a test tube experiments significant differences. But, we found that the flagellum of the clp mutant and the wild type were similar. It was observed that the clp mutant exhibited reductive production of EPS. By using leaf-cutting, susceptible host IR24 was inoculated, the clp mutant reduced pathogenicity. But, like the wild-type strain, the mutant strain could also stimulate HR in nonhost tobacco. Speculate the clp gene has effected on virulence, flagella and chemotaxis of Xanthomonas oryzae pv, oryzae.