The Functional Study Of HpaA Gene In Xanthomonas Campestris Pv. Campestris

Xanthomonas campestris pv campestris secrete a lot of effectors into plants to facilitate bacterial infection via the type ? secretion system, causing crucifers black rot. Protein HpaA widely exists in Xanthomonas. Previous research has shown that HpaAxcv85-10was proved to be a type ? effector and participated in the secretory process of other effectors in Xanthomonas campestris pv.vesicatoria. However, the function and mechanism of HpaA is not clear in Xcc. We found that HpaA was required for the total toxicity of Xcc8004in cabbage, radish, Arabidopsis thaliana and also required for the hypersensitive response in tobacco through gene knockout and bacterial inoculation experiments using Xcc8004and plant interaction model. Further study showed that HpaA could interact with HpaB and affect the secretion of XopA, AvrXccE1, XopR, AvrA1, AvrA2, hrpW et al. Western Blot proved that the secretion of HpaAxcc8004depended on the structure gene hrcV of type ?secretion system, which suggested HpaAxcc8004may function as type ? effector. Subcellular localization showed that HpaAXcc8004localized in the plant cell nucleus and had two nuclear localization signals. Dual luciferase analysis system suggested HpaAxcc8004promoted flg22-induced FRK1::LUC gene expression. Through constructing hpaA transgenic Arabidopsis thaliana, we found that HpaAxCC8004promoted hydrogen peroxide accumulation and callose deposition in plant. It reduced the chlorosis symptoms in Arabidopsis caused by DC3000and Xcc8004.