中文摘要：

【目的】基因组学揭示,水稻细菌性条斑病菌（Xanthomonas oryzae pv. oryzicola,Xoc）中存在与丁香假单胞菌（Pseudomonas syringae pv. tomato,Pst）中通过Ⅲ型分泌系统分泌的HopQ1-1同源的XopQ1Xoc,但其是否为T3S效应分子以及在病菌致病性中的功能并不清楚。【方法】通过基因敲除技术,获得了水稻条斑病菌xopQ1Xoc的突变体。【结果】致病性测定结果发现,xopQ1Xoc突变后,病菌在水稻上的毒性增强,细菌生长能力增强。非常有意义的是,xopQ1Xoc突变体菌液浓度为3×108CFU/mL时仍能在烟草上激发过敏反应,但在浓度为104CFU/mL时,8d后可在烟草上产生坏死症状。功能互补结果显示,xopQ1Xoc能够恢复突变体在水稻上的毒性至野生型水平和在烟草上丧失产生坏死病斑的能力。Western杂交结果显示,XopQ1Xoc不能通过T3S装置进行分泌。【结论】XopQ1Xoc是水稻条斑病菌T3S效应分子,可能作用于植物的免疫系统,有利于病害的发展。为进一步揭示水稻-黄单胞菌互作的分子机理提供了科学线索。

英文摘要：

【Objective】 The genome bioinformatics of X.oryzae pv.oryzicola（Xoc）,which is the causal agent of bacterial leaf streak in rice,reveals that there is a XopQ1Xoc in the pathogen homologous to HopQ1-1 secreted through type-Ⅲ secretion system（T3S） in Pseudomonas syringae pv.tomato DC3000,causing bacterial speck diseases in tomato.However,it is unclear whether XopQ1Xoc is a T3S effector or not and what roles it takes in virulence of Xoc in rice.【Method】The mutant of Xoc in the xopQ1Xoc gene was generated by knocking-out technique through marker-exchange.【Result】 Pathogenicity assays demonstrated that the virulence of the mutant in rice was stronger than that caused by Xoc wild-type strain RS105 and the bacterial growth of the mutant in rice tissue was enhanced.Intriguingly,the xopQ1Xoc mutant at 108 CFU/mL still induced hypersensitive response in tobacco,but caused necrosis lesions at 104 CFU/mL after injected into tobacco leaves for 8 days.The complementation assay indicated that the xopQ1Xoc gene restored virulence and bacterial growth in rice and the ability not to cause nescrosis lesions in tobacco to the wild-type RS105.Immunobloting assay confirmed that XopQ1Xoc was not secreted through T3S apparatus if the component HrcV was mutated.【Conclusion】 These results strongly suggested that XopQ1Xoc is a T3S effector of X.oryzae pv.oryzicola contributing strong virulence to the pathogen in rice by suppressing an unknown target in plant immunity system.This study has provided a basis to understand molecular mechanisms in Xoc-rice interactions.