Huh Sung Un, Cevik Volkan, Ding Pingtao, Duxbury Zane, Ma Yan, Tomlinson Laurence, Sarris Panagiotis F, Jones Jonathan D G
The Sainsbury Laboratory, Norwich Research Park, Colney Lane, Norwich, United Kingdom.
Department of Biology and Biochemistry, University of Bath, Bath, United Kingdom.
PLoS Pathog. 2017 May 5;13(5):e1006376. doi: 10.1371/journal.ppat.1006376. eCollection 2017 May.
Plant NLR (Nucleotide-binding domain and Leucine-rich Repeat) immune receptor proteins are encoded by Resistance (R) genes and confer specific resistance to pathogen races that carry the corresponding recognized effectors. Some NLR proteins function in pairs, forming receptor complexes for the perception of specific effectors. We show here that the Arabidopsis RPS4 and RRS1 NLR proteins are both required to make an authentic immune complex. Over-expression of RPS4 in tobacco or in Arabidopsis results in constitutive defense activation; this phenotype is suppressed in the presence of RRS1. RRS1 protein co-immunoprecipitates (co-IPs) with itself in the presence or absence of RPS4, but in contrast, RPS4 does not associate with itself in the absence of RRS1. In the presence of RRS1, RPS4 associates with defense signaling regulator EDS1 solely in the nucleus, in contrast to the extra-nuclear location found in the absence of RRS1. The AvrRps4 effector does not disrupt RPS4-EDS1 association in the presence of RRS1. In the absence of RRS1, AvrRps4 interacts with EDS1, forming nucleocytoplasmic aggregates, the formation of which is disturbed by the co-expression of PAD4 but not by SAG101. These data indicate that the study of an immune receptor protein complex in the absence of all components can result in misleading inferences, and reveals an NLR complex that dynamically interacts with the immune regulators EDS1/PAD4 or EDS1/SAG101, and with effectors, during the process by which effector recognition is converted to defense activation.
植物NLR（核苷酸结合结构域和富含亮氨酸重复序列）免疫受体蛋白由抗性（R）基因编码，并赋予对携带相应识别效应子的病原体小种的特异性抗性。一些NLR蛋白成对发挥作用，形成用于感知特定效应子的受体复合物。我们在此表明，拟南芥RPS4和RRS1 NLR蛋白都是形成真正免疫复合物所必需的。在烟草或拟南芥中过表达RPS4会导致组成型防御激活；在存在RRS1的情况下，这种表型会受到抑制。无论有无RPS4，RRS1蛋白都能与自身进行共免疫沉淀（co-IP），但相比之下，在没有RRS1的情况下，RPS4不会与自身结合。在存在RRS1的情况下，RPS4仅在细胞核中与防御信号调节因子EDS1结合，这与在没有RRS1时发现的核外定位形成对比。在存在RRS1的情况下，AvrRps4效应子不会破坏RPS4-EDS1的结合。在没有RRS1的情况下，AvrRps4与EDS1相互作用，形成核质聚集体，PAD4的共表达会干扰其形成，但SAG101不会。这些数据表明，在缺少所有组分的情况下研究免疫受体蛋白复合物可能会导致误导性的推断，并揭示了一种在效应子识别转化为防御激活的过程中与免疫调节因子EDS1/PAD4或EDS1/SAG101以及效应子动态相互作用的NLR复合物。
