DataSheet_1_Disease resistance features of the executor R gene Xa7 reveal novel insights into the interaction between rice and Xanthomonas oryzae pv. oryzae.pdf

Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is a widespread and destructive disease in rice production. Previously, we cloned an executor R gene, Xa7, which confers durable and broad-spectrum resistance to BB. Here, we further confirmed that the transcription activator-like effector (TALE) AvrXa7 in Xoo strains could directly bind to the effector-binding element (EBE) in the promoter of the Xa7 gene. Other executor R genes (Xa7, Xa10, Xa23, and Xa27) driven by the promoter of the Xa7 gene could be activated by AvrXa7 and trigger the hypersensitive response (HR) in tobacco leaves. When the expression of the Xa23 gene was driven by the Xa7 promoter, the transgenic rice plants displayed a similar resistance spectrum as the Xa7 gene, demonstrating that the disease resistance characteristics of executor R genes are mainly determined by their induction patterns. Xa7 gene is induced locally by Xoo in the infected leaves, and its induction not only inhibited the growth of incompatible strains but also enhanced the resistance of rice plants to compatible strains, which overcame the shortcomings of its race-specific resistance. Transcriptome analysis of the Xa7 gene constitutive expression in rice plants displayed that Xa7-mediated disease resistance was related to the biosynthesis of lignin and thus enhanced resistance to Xoo. Overall, our results provided novel insights and important resources for further clarifying the molecular mechanisms of the executor R genes.

由稻黄单胞菌稻致病变种（Xanthomonas oryzae pv. oryzae, Xoo）引发的白叶枯病（Bacterial blight, BB）是水稻生产中分布广泛且危害严重的病害。本团队此前已克隆得到执行型抗病基因（executor R gene）Xa7，该基因可赋予水稻对白叶枯病持久且广谱的抗性。本研究进一步证实，Xoo菌株中的转录激活因子样效应物（transcription activator-like effector, TALE）AvrXa7能够直接结合Xa7基因启动子区域内的效应物结合元件（effector-binding element, EBE）。由Xa7启动子驱动的其他执行型抗病基因（包括Xa7、Xa10、Xa23与Xa27）均可被AvrXa7激活，并在烟草叶片中触发过敏反应（hypersensitive response, HR）。当Xa23基因由Xa7启动子驱动时，转基因水稻植株展现出与Xa7基因相似的抗病谱，这表明执行型抗病基因的抗病特性主要由其诱导模式决定。Xa7基因会在Xoo侵染的叶片中被局部诱导，其诱导表达不仅可抑制非亲和菌株的增殖，还能增强水稻对亲和菌株的抗性，从而克服了其小种专化抗性的缺陷。对Xa7基因组成型表达的转基因水稻进行转录组分析后发现，Xa7介导的抗病性与木质素生物合成相关，进而提升了水稻对Xoo的抗性。综上，本研究结果为进一步阐明执行型抗病基因的分子机制提供了全新的见解与重要的研究资源。