Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA.
Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA; Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA; Carolina Center for Genome Sciences, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA; Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA.
Cell Host Microbe. 2014 Oct 8;16(4):484-94. doi: 10.1016/j.chom.2014.09.004.
Plants detect microbes via two functionally interconnected tiers of immune receptors. Immune detection is suppressed by equally complex pathogen mechanisms. The small plasma-membrane-tethered protein RIN4 negatively regulates microbe-associated molecular pattern (MAMP)-triggered responses, which are derepressed upon bacterial flagellin perception. We demonstrate that recognition of the flagellin peptide MAMP flg22 triggers accumulation of RIN4 phosphorylated at serine 141 (pS141) that mediates derepression of several immune outputs. RIN4 is targeted by four bacterial type III effector proteins, delivered temporally after flagellin perception. Of these, AvrB acts with a host kinase to increase levels of RIN4 phosphorylated at threonine 166 (pT166). RIN4 pT166 is epistatic to RIN4 pS141. Thus, AvrB contributes to virulence by enhancing "rerepression" of immune system outputs. Our results explain the evolution of independent effectors that antagonize accumulation of RIN4 pS141 and of a specific plant intracellular NLR protein, RPM1, which is activated by AvrB-mediated accumulation of RIN4 pT166.
植物通过两层功能上相互关联的免疫受体来检测微生物。免疫检测受到同样复杂的病原体机制的抑制。小的质膜连接蛋白 RIN4 负调控微生物相关分子模式 (MAMP) 触发的反应，而细菌鞭毛蛋白感知后会解除这种抑制。我们证明，flagellin 肽 MAMP flg22 的识别触发了 RIN4 在丝氨酸 141 处磷酸化 (pS141) 的积累，这介导了几种免疫输出的去抑制。RIN4 是四个细菌 III 型效应蛋白的靶标，这些蛋白在鞭毛蛋白感知后被递送到宿主中。其中，AvrB 与宿主激酶一起作用，增加 RIN4 在苏氨酸 166 处磷酸化 (pT166) 的水平。RIN4 pT166 对 RIN4 pS141 具有上位性。因此，AvrB 通过增强免疫系统输出的“再抑制”来促进毒力。我们的结果解释了拮抗 RIN4 pS141 积累的独立效应子和特定植物细胞内 NLR 蛋白 RPM1 的进化，AvrB 介导的 RIN4 pT166 积累激活了 RPM1。
