中文摘要：

水稻条斑病菌（Xanthomonas oryzae pv.oryzicola,Xoc）的hrp基因簇编码Ⅲ型分泌系统（T3SS）,将致病性效应分子注入寄主细胞中,决定在寄主水稻（Oryza sativa）的致病性（pathogenicity）和在非寄主烟草（Nicotiana benthamiana）的过敏性反应（hypersensitive response,HR）。Hpa1可在烟草上激发HR,HpaB是T3SS的出口控制蛋白。为了解Hpa1与HpaB是否共同决定病菌Xoc在烟草上的HR以及在水稻上的致病性,本研究通过基因敲除方式分别获得了hpa1和hpaB的单突变体以及hpa1hpaB双突变体。致病性测定结果显示,hpa1突变体在水稻上的毒性减弱,在烟草上仍能激发HR;hpaB单突变体以及hpa1和hpaB双突变体在烟草上仍能激发HR,但对水稻无致病性。这暗示,水稻条斑病菌除Hpa1外,还存在不依赖HpaB分泌的未知Harpin蛋白。免疫杂交结果显示,hpaB突变后,效应分子XopQXoc不能通过T3SS进行分泌。这提示,HpaB控制了T3SS效应分子的分泌,从而决定Xoc对水稻的致病性。这些结果为进一步发掘水稻黄单胞菌中的未知Harpin蛋白以及分析依赖或不依赖HpaB进行分泌的T3SS效应分子与水稻的互作关系,提供了科学线索。

英文摘要：

The hrp genes of Xanthomonas oryzae pv. oryzicola （Xoc） encode type Ⅲ secretion system （T3SS） and deliver T3SS effectors into host cells to trigger hypersensitive response （HR） on nonhost plants tobacco （Nicotiana benthamiana） and pathogenicity on rice （Oryza sativa）. Hpa1 protein triggers HR on tobacco and HpaB is an exit protein for T3SS. However, it is still unclear whether hpa1 and hpaB genes together determine Xoc to cause pathogenicity on rice and to trigger HR on tobacco. In this study, we acquired the hpa1 and hpaB single mutant as well as the hpa1hpaB double mutant. In planta assay showed that the hpa1 mutant reduced the virulence of Xoc on rice, whereas still maintained the capacity of triggering HR on tobacco. Both of the hpaB mutant and the hpa1hpaB double mutant induced HR on tobacco, but abolished pathogenicity on rice. These results indicated that other unknown harpin（s） exist（s） in Xoc, which is （are） HpaB-independent effector（s）. Immunobloting assay showed that XopQ1Xoc was not secreted through T3SS when hpaB gene was mutated, suggesting that HpaB control the secretion of T3SS effectors that are considered to be pathogenic factors. The above evidences provide the clues to elucidate novel unknown harpin（s） and to analyze the molecular interaction of HpaB-dependent and HpaB-independent effectors with rice.