1 State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
2 College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China; and.
Mol Plant Microbe Interact. 2017 Jun;30(6):502-512. doi: 10.1094/MPMI-01-17-0017-R. Epub 2017 May 8.
Bacterial pathogen Pseudomonas syringae delivers diverse type III effectors into host cells to interfere with their immune responses. One of the effectors, AvrB, targets a host guardee protein RIN4 and induces RIN4 phosphorylation in Arabidopsis. Phosphorylated RIN4 activates the immune receptor RPM1 to mount defense. AvrB-induced RIN4 phosphorylation depends on RIPK, a receptor-like cytoplasmic kinase (RLCK). In this study, we found several other RLCKs that were also able to phosphorylate RIN4. We demonstrated that these RLCKs formed a complex with RIPK and were functionally redundant to RIPK. We also found that unphosphorylated RIN4 was epistatic to phosphorylated RIN4 in terms of RPM1 activation. AvrB-induced RLCK gene expression and phosphorylated RIN4-triggered RPM1 activation required RAR1, a central regulator in plant innate immunity. Our results unravel a mechanism in which plants employ multiple kinases to hyperphosphorylate the guardee protein RIN4 to ensure immune activation during pathogen invasion.
细菌病原体丁香假单胞菌将多种类型 III 效应蛋白输送到宿主细胞中，以干扰其免疫反应。其中一种效应蛋白 AvrB 靶向宿主靶标蛋白 RIN4 并诱导拟南芥中 RIN4 的磷酸化。磷酸化的 RIN4 激活免疫受体 RPM1 以启动防御。AvrB 诱导的 RIN4 磷酸化依赖于 RIPK，一种受体样细胞质激酶 (RLCK)。在这项研究中，我们发现了其他几种也能够磷酸化 RIN4 的 RLCKs。我们证明这些 RLCKs 与 RIPK 形成复合物，并且在功能上与 RIPK 冗余。我们还发现，未磷酸化的 RIN4 在 RPM1 激活方面是磷酸化 RIN4 的上位基因。AvrB 诱导的 RLCK 基因表达和磷酸化 RIN4 触发的 RPM1 激活需要 RAR1，这是植物先天免疫中的一个中央调节剂。我们的研究结果揭示了一种机制，植物利用多种激酶使靶标蛋白 RIN4 过度磷酸化，以确保在病原体入侵期间免疫激活。
