Department of Biology, Lahore University of Management Sciences, Sector U, DHA, Lahore, Pakistan.
Department of Horticulture and Crop Science, The Ohio State University, Columbus, OH, 43210, USA.
Plant Cell Rep. 2021 Dec;40(12):2341-2356. doi: 10.1007/s00299-021-02771-9. Epub 2021 Sep 5.
RIN4 homologs from important crop species differ in their ability to prevent ectopic activity of the nucleotide binding-leucine rich repeat resistance protein, RPS2. Pathogens deploy virulence effectors to perturb host processes. Plants utilize intracellular resistance (R) proteins to recognize pathogen effectors either by direct interaction or indirectly via effector-mediated perturbations of host components. RPM1-INTERACTING PROTEIN4 (RIN4) is a plant immune regulator that mediates the indirect activation of multiple, independently evolved R-proteins by multiple, unrelated effector proteins. One of these, RPS2 (RESISTANT TO P. SYRINGAE2), is activated upon cleavage of Arabidopsis (At)RIN4 by the Pseudomonas syringae effector AvrRpt2. To gain insight into the AvrRpt2-RIN4-RPS2 defense-activation module, we compared the function of AtRIN4 with RIN4 homologs present in a diverse range of plant species. We selected seven homologs containing conserved features of AtRIN4, including two NOI (Nitrate induced) domains, each containing a predicted cleavage site for AvrRpt2, and a C-terminal palmitoylation site predicted to mediate membrane tethering of the proteins. Palmitoylation-mediated tethering of AtRIN4 to the plasma membrane and cleavage by AvrRpt2 are required for suppression and activation of RPS2, respectively. While all seven homologs are localized at the plasma membrane, only four suppress RPS2 when transiently expressed in Nicotiana benthamiana. All seven homologs are cleaved by AvrRpt2 and, for those homologs that are able to suppress RPS2, cleavage relieves suppression of RPS2. Further, we demonstrate that the membrane-tethered, C-terminal AvrRpt2-generated cleavage fragment is sufficient for the suppression of RPS2. Lastly, we show that the membrane localization of RPS2 is unaffected by its suppression or activation status.
来自重要作物物种的 RIN4 同源物在防止核苷酸结合富含亮氨酸重复的抗病蛋白 RPS2 的异位活性方面存在差异。病原体利用毒力效应物来扰乱宿主过程。植物利用细胞内抗性（R）蛋白通过直接相互作用或间接通过效应物介导的宿主成分的扰动来识别病原体效应物。RPM1-INTERACTING PROTEIN4（RIN4）是一种植物免疫调节剂，可通过多种不相关的效应蛋白间接激活多种独立进化的 R 蛋白。其中之一，RPS2（对 P. SYRINGAE2 的抗性），在拟南芥（At）RIN4 被丁香假单胞菌效应物 AvrRpt2 切割时被激活。为了深入了解 AvrRpt2-RIN4-RPS2 防御激活模块，我们比较了存在于多种植物物种中的 AtRIN4 同源物的功能。我们选择了七个包含 AtRIN4 保守特征的同源物，包括两个 NOI（硝酸盐诱导）结构域，每个结构域都包含一个预测的 AvrRpt2 切割位点，以及一个预测的棕榈酰化位点，该位点介导蛋白质的膜锚定。AtRIN4 的棕榈酰化介导的质膜锚定和 AvrRpt2 的切割分别是抑制和激活 RPS2 的必要条件。虽然这七个同源物都定位于质膜上，但只有四个在瞬时表达于 Nicotiana benthamiana 时抑制 RPS2。所有七个同源物都被 AvrRpt2 切割，并且对于那些能够抑制 RPS2 的同源物，切割缓解了对 RPS2 的抑制。此外，我们证明了膜结合的、C 末端 AvrRpt2 产生的切割片段足以抑制 RPS2。最后，我们表明 RPS2 的膜定位不受其抑制或激活状态的影响。
