稻瘟菌无毒基因Avrpi9的克隆和变异机制研究

Rice blast is one of the three major diseases of rice, and Magnaporthe oryzae is the pathogens. The most economic and effective prevention and control of rice blast disease is the breeding and popularization of resistance varieties. Rice resistance to rice blast not only depended on R gene but also avirulence gene, only both of them, which specific recognized each other, present together performances for resistance reaction. Cloning and mutation mechanism research of avirulence gene will be helpful for clarifying the mechanism and durability of rice resistance to rice blast disease. Ror1 contained avrPi9 is a strain mutated from 26 mixed AvrPi9 strains by vaccinization. And it has been found that R88-002 is the mutation source strain. This project has been re-sequenced their genome, compared genomics to gain the genes which itself and transposon insertion on its' promoter region difference as the candidate gene of AvrPi9. Than, the candidate gene will be scanned by molecular markers between avirulent/virulent strain. Finally, AvrPi9 will be cloned by function complementary verification, and that will reveals mutation mechanism of avirulence gene in rice blast.

稻瘟菌（Magnaporthe oryzae）是水稻三大病害之一稻瘟病的病原物。防控稻瘟病最为经济和有效的手段是抗病品种的选育和推广。在生产实践中，抗性品种连续种植3至5年后,抗性就会明显衰退。水稻抗稻瘟病的持久性与稻瘟菌的无毒基因关系密切，只有在水稻和稻瘟菌各自携带特异性识别的抗病基因和无毒基因时才表现为抗病反应。稻瘟菌无毒基因的克隆和变异机制研究对于深入阐明水稻抗稻瘟病机制和抗病的持久性具有非常重要的意义。Ror1是通过26个AvrPi9无毒菌株连续混合接种获得avrPi9有毒突变体菌株。经过鉴定，其中R88-002是其突变来源菌株。本项目将它们基因组重测序，通过比较基因组学手段，获得在基因本身和基因启动子区转座子插入差异的基因作为AvrPi9的候选基基因，经过多个无毒/有毒菌株分子标记扫描和功能互补验证，最终克隆无毒基因AvrPi9，揭示稻瘟菌无毒基因变异机制。

稻瘟菌引起的稻瘟病仍然是威胁水稻稳产的主要病害。推广抗性品种是最经济绿色的防控手段。然而稻瘟病的抗性是“基因对基因”互作的结果，除了水稻抗性基因之外，对应的稻瘟菌无毒基因是关键。田间稻瘟菌群体变异迅速，在单一品种抗性水稻选择压力下，无毒基因变异的有毒菌株形成优势种群，从而突破水稻抗性爆发稻瘟病。这导致生产上抗性品种连续种植3-5年后就失效。因此，稻瘟菌无毒基因的克隆和变异机制研究对于深入阐明水稻抗稻瘟病机制和抗病的持久性具有非常重要的意义。本项目通过Pi9有毒突变体菌株ROR1和它的野生型菌株R88-002之间的全基因组测序比较，在23个AvrPi9候选基因基础上成功到了无毒基因AvrPi9（MGG12655）。它与Pi9蛋白之间没有直接互作，它的丢失也不影响对非Pi9水稻的致病能力。菌株间AvrPi9高度保守，除了75-5和ROR1之外序列100%一致。