Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America.
PLoS Pathog. 2011 Nov;7(11):e1002318. doi: 10.1371/journal.ppat.1002318. Epub 2011 Nov 3.
EDS1, PAD4, and SAG101 are common regulators of plant immunity against many pathogens. EDS1 interacts with both PAD4 and SAG101 but direct interaction between PAD4 and SAG101 has not been detected, leading to the suggestion that the EDS1-PAD4 and EDS1-SAG101 complexes are distinct. We show that EDS1, PAD4, and SAG101 are present in a single complex in planta. While this complex is preferentially nuclear localized, it can be redirected to the cytoplasm in the presence of an extranuclear form of EDS1. PAD4 and SAG101 can in turn, regulate the subcellular localization of EDS1. We also show that the Arabidopsis genome encodes two functionally redundant isoforms of EDS1, either of which can form ternary complexes with PAD4 and SAG101. Simultaneous mutations in both EDS1 isoforms are essential to abrogate resistance (R) protein-mediated defense against turnip crinkle virus (TCV) as well as avrRps4 expressing Pseudomonas syringae. Interestingly, unlike its function as a PAD4 substitute in bacterial resistance, SAG101 is required for R-mediated resistance to TCV, thus implicating a role for the ternary complex in this defense response. However, only EDS1 is required for HRT-mediated HR to TCV, while only PAD4 is required for SA-dependent induction of HRT. Together, these results suggest that EDS1, PAD4 and SAG101 also perform independent functions in HRT-mediated resistance.
EDS1、PAD4 和 SAG101 是植物对多种病原体免疫的常见调节剂。EDS1 与 PAD4 和 SAG101 相互作用，但尚未检测到 PAD4 和 SAG101 之间的直接相互作用，这导致人们提出 EDS1-PAD4 和 EDS1-SAG101 复合物是不同的。我们表明 EDS1、PAD4 和 SAG101 存在于植物体内的单个复合物中。虽然该复合物主要定位于核内，但在存在核外形式的 EDS1 时，它可以被重定向到细胞质中。PAD4 和 SAG101 反过来又可以调节 EDS1 的亚细胞定位。我们还表明，拟南芥基因组编码 EDS1 的两种功能上冗余的同工型，其中任一种都可以与 PAD4 和 SAG101 形成三元复合物。同时突变两个 EDS1 同工型对于消除 R 蛋白介导的对芜菁花叶病毒（TCV）的抗性以及表达 avrRps4 的丁香假单胞菌是必需的。有趣的是，与它在细菌抗性中作为 PAD4 替代物的功能不同，SAG101 是 R 介导的对 TCV 的抗性所必需的，因此暗示了三元复合物在这种防御反应中的作用。然而，只有 EDS1 是 HRT 介导的对 TCV 的 HR 所必需的，而只有 PAD4 是 SA 依赖性诱导 HRT 所必需的。总之，这些结果表明 EDS1、PAD4 和 SAG101 也在 HRT 介导的抗性中发挥独立的功能。
