白叶枯病作为水稻"三大病害"之一，严重影响水稻的生长发育与生产。水稻抗白叶枯病基因Xa7具有高抗、广谱的抗病特性，比许多抗病基因的抗性更加持久，因此Xa7基因在植物抗病机理研究与水稻育种中都具有重要价值。本申请项目在已将Xa7基因定位于水稻第6染色体上50kb区间内、并确定Xa7候选基因的工作基础上，通过候选基因的转基因功能验证，克隆Xa7基因；分析Xa7基因的组织表达特征与亚细胞定位情况、Xa7基因的抗病应答及其信号途径、Xa7与无毒基因avrXa7的互作模式, 初步阐明Xa7基因的生物学功能及其与病原菌互作的抗病分子机制。本申请项目的完成将丰富植物抗病分子机制的理论知识，并有助于水稻抗病分子育种的实践，同时也为抗病基因与病原菌互作模式研究增添新的素材。

Rice bacterial blight (BB), caused by Xanthomonas oryzae pv. Oryzae (Xoo), is a devastating disease in rice production worldwide. Xa7, a BB resistant gene originally identified in rice cv. DV85, confers high-level, broad-spectrum and most durable resistance to Xoo. Therefore, the Xa7 gene could have huge potentiality in rice breeding. Our previous studies have mapped the Xa7 gene within a 50 kb region on rice chromosome 6 and the putative candidate gene encoding Xa7 has been identified. In this project, we will confirm the identity of Xa7 gene by transgenic functional complementation studies; After confirming the identity of Xa7, we will study the mode of interaction between Xa7 and AvrXa7, which will help to understand the molecular mechanism of Xa7-mediated resistance against Xoo; In addition, we will analyze both the tempo-spatial expression patterns of Xa7 gene in response to Xoo infection and subcellular localization of Xa7 protein; Furthermore, we will identify genes downstream of Xa7-mediated resistant pathway using microarray. Together, the results generated by this proposed project will broaden the knowledge of molecular mechanism of disease resistance in plant, improve the molecular breeding of Xoo resistance in rice, and provid of a new line of sight on the interaction model between resistant gene and pathogen.