申请人前期研究表明，水稻可以利用内源小RNA调节自身免疫；稻瘟菌则既可以通过控制水稻內源小RNA又可以利用自身小RNA抑制水稻抗病性。小RNA必须与AGO蛋白结合才能调控靶标基因的表达。18个水稻AGO中，只有AGO2严重影响对稻瘟病的抗性。因此，本项目拟分离与水稻AGO2结合的小RNA，比较它们在抗、感品种被侵染前后的表达差异，筛选在互作中差异表达的水稻內源小RNA和稻瘟菌小RNA；鉴定它们在水稻中的靶标基因。针对稻瘟菌小RNA，通过稻瘟菌基因敲除和水稻过表达技术，研究其在致病以及在寄主靶标基因调控中的作用；对水稻內源小RNA及其靶标，分别构建缺失和过表达水稻，考察其抗性变化；利用多种手段研究稻瘟菌诱导水稻小RNA以及小RNA调控靶标基因表达的分子机理。本研究将揭示水稻AGO2介导的基因沉默途径在水稻与稻瘟菌互作中的功能与作用机制，为开发有效的稻瘟病控制技术提供分子靶标和理论支持。

The rice blast disease is one of the most devastating rice disease in China, causing dramatic yield loss each year. Small RNA (sRNA) is capable of targeting and regulating the expression of resistance (R) genes or loci, which are of great potential in developing durable and effective blast disease control methods. In the 18 rice AGO proteins, OsAGO2 is the most critical RNA silencing component associated with rice resistance to the blast disease. Our project is to isolate and enrich OsAGO2-assocated sRNAs and study their regulatory roles in resistance to the blast disease. By comparing the expression variation of sRNAs in resistant and susceptible rice varieties that are infected by the same M. oryzae strain, we will be able to identify rice sRNAs that participate either in the regulation of rice defense, or the pathogenicity of M. oryzae; by discriminating rice endogenous sRNAs from these originated from M. oryzae but are secreted into rice cells and regulate rice defense-related genes, we will be able to investigate how sRNAs are employed in the arm-race between rice and M. oryzae interaction; by creating and testing deletion and overexpression rice transgenic lines, we will be able to validate the functions of sRNA candidates and their target genes in resistance to M. oryzae infection. Based on these results, we will be able to summarize the mode of action of sRNAs in rice resistance to the blast disease, particularly these OsAGO2-associated sRNAs. Our study is not only of great significance for developing effective blast disease control methods, but also important for an in-depth understanding of the regulatory roles of sRNAs in resistance to other crop diseases.