Ma Xian-Feng, Li Yan, Sun Jin-Long, Wang Ting-Ting, Fan Jing, Lei Yang, Huang Yan-Yan, Xu Yong-Ju, Zhao Ji-Qun, Xiao Shunyuan, Wang Wen-Ming
Rice Research Institute, Sichuan Agricultural University, Chengdu 611130, ChinaInstitute of Bioscience and Biotechnology Research and Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD 20850, USAThese authors contributed equally to this work.
Rice Research Institute, Sichuan Agricultural University, Chengdu 611130, ChinaThese authors contributed equally to this work.
Plant Cell Physiol. 2014 Aug;55(8):1484-96. doi: 10.1093/pcp/pcu080. Epub 2014 Jun 4.
Broad-spectrum disease resistance is a highly valuable trait in plant breeding and attracts special attention in research. The Arabidopsis gene locus RESISTANCE TO POWDERY MILDEW 8 (RPW8) contains two adjacent homologous genes, RPW8.1 and RPW8.2, and confers broad-spectrum resistance to powdery mildew. Remarkably, the RPW8.2 protein is specifically localized to the extrahaustorial membrane (EHM) encasing the feeding structure of powdery mildew whereby RPW8.2 activates haustorium-targeted defenses. Here, we show that ectopic expression of the yellow fluorescent protein (YFP)-tagged RPW8.1 from the native promoter leads to unique cell death lesions and enhances resistance to virulent fungal and oomycete pathogens that cause powdery mildew and downy mildew diseases, respectively. In powdery mildew-infected plants, RPW8.1-YFP accumulates at higher levels in the mesophyll cells underneath the infected epidermal cells where RPW8.2-YFP is mainly expressed. This cell type-preferential protein accumulation pattern largely correlates with that of H(2)O(2) accumulation, suggesting that RPW8.1 may spatially collaborate with RPW8.2 in activation of resistance to powdery mildew. Interestingly, when ectopically expressed from the RPW8.2 promoter, RPW8.1-YFP is also targeted to the EHM of powdery mildew and the transgenic plants display resistance to both powdery mildew and downy mildew. Using YFP as a reporter, we further reveal that the RPW8.1 promoter is constitutively active but induced to higher levels in cells at the infection site, whereas the RPW8.2 promoter is activated specifically in cells at the infection site. Taken together, our results suggest that RPW8.1 (and its promoter) is functionally distinct from RPW8.2 and may have a higher potential in engineering broad-spectrum resistance in plants.
广谱抗病性是植物育种中一项极具价值的性状，在研究中备受关注。拟南芥基因座抗白粉病8（RPW8）包含两个相邻的同源基因RPW8.1和RPW8.2，赋予对白粉病的广谱抗性。值得注意的是，RPW8.2蛋白特异性定位于包裹白粉菌取食结构的吸器外膜（EHM），由此激活针对吸器的防御。在此，我们表明从天然启动子异位表达黄色荧光蛋白（YFP）标记的RPW8.1会导致独特的细胞死亡损伤，并增强对分别引起白粉病和霜霉病的致病真菌和卵菌病原体的抗性。在感染白粉病的植物中，RPW8.1 - YFP在受感染表皮细胞下方的叶肉细胞中积累水平更高，而RPW8.2 - YFP主要在这些叶肉细胞中表达。这种细胞类型偏好的蛋白积累模式与H(2)O(2)积累模式在很大程度上相关，表明RPW8.1可能在空间上与RPW8.2协同激活对白粉病的抗性。有趣的是，当从RPW8.2启动子异位表达时，RPW8.1 - YFP也靶向白粉菌的EHM，并且转基因植物对白粉病和霜霉病均表现出抗性。利用YFP作为报告基因，我们进一步揭示RPW8.1启动子组成型活跃，但在感染部位的细胞中被诱导到更高水平，而RPW8.2启动子在感染部位的细胞中特异性激活。综上所述，我们的结果表明RPW8.1（及其启动子）在功能上与RPW8.2不同，并且在植物广谱抗性工程中可能具有更高的潜力。
