水稻条斑病菌hrpB1基因决定寄主致病性和非寄主过敏反应的功能研究  

The hrpB1 gene of Xanthomonas oryzae pv.oryzicola is required for hypersensitive response in nonhost tobacco and pathogenicity in host rice

作　　者：刘之洋[1] 邹丽芳[2] 邹华松[2] 陈功友[1,2] 

机构地区：[1]南京农业大学植物保护学院农业部病虫监测与治理重点开放实验室,南京210095 [2]上海交通大学农业与生物学院,上海200240

出　　处：《植物病理学报》2010年第6期579-586,共8页Acta Phytopathologica Sinica

基　　金：国家自然科学基金资助项目(3071010390230671354);公益性行业(农业)科研专项(NYHYZX07-056)

摘　　要：水稻条斑病菌(Xanthomonas oryzaepv.oryzicola,Xoc)的hrp基因决定了病原菌在非寄主植物上的过敏反应(hypersensitive response,HR)和在寄主植物上的致病性(pathogenicity),基因产物形成Ⅲ型分泌系统(type-Ⅲ secretion system,T3SS)将致病性效应分子注入寄主细胞从而引起水稻产生抗病性或者感病性反应。以位于hrpB操纵单元的首个hr-pB1基因为对象,通过基因敲除方式对其进行了突变,发现hrpB1突变体丧失了在水稻上的致病性和在烟草上激发HR的能力,并且在水稻组织中的生长能力显著降低。RT-PCR测定结果表明,hrpB1的转录表达受HrpG和HrpX的正调控。免疫杂交结果显示,HrpB1蛋白可通过T3SS进行分泌。这些结果不仅明确了hrpB1基因在病原菌致病性中的功能,而且提示了hrp结构基因不仅仅局限于形成Ⅲ型分泌系统,部分hrp基因产物本身也通过Ⅲ型系统分泌到胞外,并且可能起到效应分子的功能。Xanthomonas oryzae pv.oryzicola（Xoc） hrp genes determine the hypersensitive response（HR） in nonhost or resistant host and pathogenicity in host plant.The Hrp products assemble the type Ⅲ secretion system（T3SS） to deliver T3S effectors into rice cell which lead to resistance or susceptibility for pathogen infection.In this study,the hrpB1 gene was mutated by allelic exchange in Xoc.It was found that hrpB1 mutant lost pathogenicity in rice and the ability to excite HR in tobacco.In contrast,the growth of mutant reduced dramatically in leaf tissue of rice.RT-PCR showed that the transcription of hrpB1 was positively regulated by two hrp regulators,HrpG and HrpX.Intriguingly,Western blot illustrated that HrpB1 protein was secreted to the outside of bacteria via T3SS apparatus.These results suggested that hrpB1 was prerequisite for HR induction in tobacco and pathogenicity in rice and may be a novel T3S effector.

关 键 词：水稻条斑病菌 致病性 过敏反应 hrpB1基因 Ⅲ型分泌系统 

分 类 号：S432.1[农业科学—植物病理学]