Resistance protein Pit interacts with the GEF OsSPK1 to activate OsRac1 and trigger rice immunity
Resistance protein Pit interacts with the GEF OsSPK1 to activate OsRac1 and trigger rice immunity
复制标题
抗性蛋白 Pit 与 GEF OsSPK1 相互作用，激活 OsRac1 并触发水稻免疫
DOI：
10.1073/pnas.1813058115
复制
发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Kawano Yoji
中科院分区：
文献类型：
--
作者：
Wang Qiong;Li Yuying;Ishikawa Kazuya;Kosami Ken-ichi;Uno Kazumi;Nagawa Shingo;Tan Li;Du Jiamu;Shimamoto Ko;Kawano Yoji
抗性（R）基因编码细胞内核苷酸结合/富含亮氨酸重复序列（NLR）家族蛋白，其作为关键的植物免疫受体诱导效应子触发的免疫（ETI）。NLR蛋白具有由N-末端可变区、中央核苷酸结合结构域和C-末端富含亮氨酸重复序列组成的三重结构域结构。R蛋白的N-末端卷曲螺旋（CC）或Toll-白介素1受体（TIR）结构域似乎充当触发免疫应答的平台，因为某些R蛋白的CC或TIR结构域的过表达足以诱导免疫应答。由于R蛋白的直接下游信号分子仍然不清楚，R蛋白调节下游信号的分子机制在很大程度上是未知的。我们以前报道过一种名为Pit的水稻R蛋白通过一个小的GTdR，OsRac 1触发ETI，尽管Pit如何激活OsRac 1尚不清楚。在这里，我们确定了OsSPK 1，一个DOCK家族的鸟嘌呤核苷酸交换因子，作为Pit和OsRac 1的激活剂的相互作用。OsSPK 1参与了两个抗病基因PitandPia对稻瘟病菌的信号传导，并促进了OsRac 1在体内外的激活。Pit的CC结构域是其与OsSPK 1结合、OsRac 1活化和诱导细胞死亡所必需的。总之，我们得出结论，OsSPK 1是Pit介导的免疫的直接和关键的信号转导靶点。我们的研究结果揭示了R蛋白如何通过直接下游分子触发ETI。
Resistance(R) genes encode intracellular nucleotide-binding/leucine-rich repeat-containing (NLR) family proteins that serve as critical plant immune receptors to induce effector-triggered immunity (ETI). NLR proteins possess a tripartite domain architecture consisting of an N-terminal variable region, a central nucleotide-binding domain, and a C-terminal leucine-rich repeat. N-terminal coiled-coil (CC) or Toll-interleukin 1 receptor (TIR) domains of R proteins appear to serve as platforms to trigger immune responses, because overexpression of the CC or TIR domain of some R proteins is sufficient to induce an immune response. Because direct downstream signaling molecules of R proteins remain obscure, the molecular mechanisms by which R proteins regulate downstream signaling are largely unknown. We reported previously that a rice R protein named Pit triggers ETI through a small GTPase, OsRac1, although how Pit activates OsRac1 is unclear. Here, we identified OsSPK1, a DOCK family guanine nucleotide exchange factor, as an interactor of Pit and activator for OsRac1. OsSPK1 contributes to signaling by two disease-resistance genes,PitandPia, against the rice blast fungusMagnaporthe oryzaeand facilitates OsRac1 activation in vitro and in vivo. The CC domain of Pit is required for its binding to OsSPK1, OsRac1 activation, and the induction of cell death. Overall, we conclude that OsSPK1 is a direct and key signaling target of Pit-mediated immunity. Our results shed light on how R proteins trigger ETI through direct downstream molecules.