Long Juying, Song Congfeng, Yan Fang, Zhou Junhui, Zhou Huanbin, Yang Bing
Key Laboratory of Monitoring and Management of Plant Diseases and Insects, Ministry of Education, Nanjing Agricultural University, Nanjing, China.
Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, United States.
Front Plant Sci. 2018 Dec 12;9:1857. doi: 10.3389/fpls.2018.01857. eCollection 2018.
pv. , the causal pathogen of bacterial blight of rice, depends on its type III secretion system and associated effector proteins to grow and colonize the vascular tissues of rice plants. The type III effectors include a family of closely related transcription activator-like (TAL) effectors and the rest of diverse effectors, so-called non-TAL effectors. Our understanding of non-TAL effectors for pathogenesis in rice blight is still limited. Here we report a feasible method to rapidly detect the activation of mitogen-activated protein kinase pathway in rice mesophyll protoplasts by the . pv. derived peptidoglycan and screen for virulent effectors that can suppress the pathogen-associated molecular pattern triggered immunity (PTI) response. Amongst 17 non-TAL effectors transiently expressed in rice cells, we found that three effectors (XopZ, XopN, and XopV) were able to suppress the peptidoglycan-triggered MAPK activation. The triple mutant of the pv. strain PXO99 lacking , , and showed additively reduced virulence. Adding back either of genes restored the virulence of the triple mutant. Our results demonstrate the collective and redundant ability of defense suppression by non-TAL effectors in causing bacterial blight of rice.
水稻白叶枯病菌（Xanthomonas oryzae pv. oryzae）依靠其三型分泌系统及相关效应蛋白在水稻植株维管组织中生长和定殖。三型效应子包括一类密切相关的转录激活样效应子（TAL效应子）家族以及其他多种效应子，即所谓的非TAL效应子。我们对水稻白叶枯病发病机制中非TAL效应子的了解仍然有限。在此，我们报道了一种可行的方法，用于通过水稻白叶枯病菌衍生的肽聚糖快速检测水稻叶肉原生质体中丝裂原活化蛋白激酶途径的激活，并筛选能够抑制病原体相关分子模式触发的免疫（PTI）反应的毒性效应子。在水稻细胞中瞬时表达的17种非TAL效应子中，我们发现三种效应子（XopZ、XopN和XopV）能够抑制肽聚糖触发的MAPK激活。水稻白叶枯病菌株PXO99缺失XopZ、XopN和XopV的三重突变体表现出毒力的累加性降低。回补任一基因均可恢复三重突变体的毒力。我们的结果证明了非TAL效应子在引起水稻白叶枯病过程中具有集体性和冗余性的防御抑制能力。
