School of Plant Sciences and Food Security, Tel Aviv University, Tel Aviv, Israel.
Department of Plant Pathology, University of California, Davis, California.
Plant Cell Environ. 2018 Oct;41(10):2313-2327. doi: 10.1111/pce.13347. Epub 2018 Jul 3.
Plant recognition and defence against pathogens employs a two-tiered perception system. Surface-localized pattern recognition receptors (PRRs) act to recognize microbial features, whereas intracellular nucleotide-binding leucine-rich repeat receptors (NLRs) directly or indirectly recognize pathogen effectors inside host cells. Employing the tomato PRR LeEIX2/EIX model system, we explored the molecular mechanism of signalling pathways. We identified an NLR that can associate with LeEIX2, termed SlNRC4a (NB-LRR required for hypersensitive response-associated cell death-4). Co-immunoprecipitation demonstrates that SlNRC4a is able to associate with different PRRs. Physiological assays with specific elicitors revealed that SlNRC4a generally alters PRR-mediated responses. SlNRC4a overexpression enhances defence responses, whereas silencing SlNRC4 reduces plant immunity. Moreover, the coiled-coil domain of SlNRC4a is able to associate with LeEIX2 and is sufficient to enhance responses upon EIX perception. On the basis of these findings, we propose that SlNRC4a acts as a noncanonical positive regulator of immunity mediated by diverse PRRs. Thus, SlNRC4a could link both intracellular and extracellular immune perceptions.
植物通过双层感知系统识别和抵御病原体。位于表面的模式识别受体（PRRs）用于识别微生物特征，而细胞内的核苷酸结合富含亮氨酸重复受体（NLRs）则直接或间接识别宿主细胞内的病原体效应子。我们利用番茄 PRR LeEIX2/EIX 模型系统，探索了信号通路的分子机制。我们鉴定出一种能够与 LeEIX2 结合的 NLR，称为 SlNRC4a（NB-LRR 是过敏性反应相关细胞死亡-4 所必需的）。共免疫沉淀实验表明，SlNRC4a 能够与不同的 PRRs 结合。使用特定诱导剂进行的生理测定表明，SlNRC4a 通常会改变 PRR 介导的反应。SlNRC4a 的过表达增强了防御反应，而沉默 SlNRC4a 则降低了植物免疫力。此外，SlNRC4a 的卷曲螺旋结构域能够与 LeEIX2 结合，并在感知到 EIX 后足以增强反应。基于这些发现，我们提出 SlNRC4a 作为由多种 PRR 介导的免疫的非典型正调控因子发挥作用。因此，SlNRC4a 可以连接细胞内和细胞外的免疫感知。
