Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), UMR 2594/441 CNRS, INRAE, 31326, Castanet-Tolosan, France.
Agriculture and Food, Commonwealth Scientific and Industrial Research Organization, Canberra, ACT 2601, Australia.
Plant J. 2023 Jun;114(6):1319-1337. doi: 10.1111/tpj.16195. Epub 2023 Apr 3.
Recent work shed light on how plant intracellular immune receptors of the nucleotide-binding leucine-rich repeat (NLR) family are activated upon pathogen effector recognition to trigger immune responses. Activation of Toll-interleukin-1 receptor (TIR) domain-containing NLRs (TNLs) induces receptor oligomerization and close proximity of the TIR domain, which is required for TIR enzymatic activity. TIR-catalyzed small signaling molecules bind to EDS1 family heterodimers and subsequently activate downstream helper NLRs, which function as Ca permeable channel to activate immune responses eventually leading to cell death. Subcellular localization requirements of TNLs and signaling partners are not well understood, although they are required to understand fully the mechanisms underlying NLR early signaling. TNLs show diverse subcellular localization while EDS1 shows nucleocytosolic localization. Here, we studied the impact of TIR and EDS1 mislocalization on the signaling activation of different TNLs. In Nicotiana benthamiana, our results suggest that close proximity of TIR domains isolated from flax L6 and Arabidopsis RPS4 and SNC1 TNLs drives signaling activation from different cell compartments. Nevertheless, both Golgi-membrane anchored L6 and nucleocytosolic RPS4 have the same requirements for EDS1 subcellular localization in Arabidopsis thaliana. By using mislocalized variants of EDS1, we found that autoimmune L6 and RPS4 TIR domain can induce seedling cell death when EDS1 is present in the cytosol. However, when EDS1 is restricted to the nucleus, both induce a stunting phenotype but no cell death. Our data point out the importance of thoroughly investigating the dynamics of TNLs and signaling partners subcellular localization to understand TNL signaling fully.
最近的研究揭示了植物细胞内核苷酸结合富含亮氨酸重复（NLR）家族的免疫受体如何在识别病原体效应子时被激活，从而引发免疫反应。Toll-白细胞介素-1 受体（TIR）结构域包含的 NLR（TNLs）的激活诱导受体寡聚化和 TIR 结构域的紧密接近，这是 TIR 酶活性所必需的。TIR 催化的小分子与 EDS1 家族异二聚体结合，随后激活下游辅助 NLR，作为 Ca 通透通道发挥作用，激活免疫反应，最终导致细胞死亡。尽管理解 NLR 早期信号转导的机制需要充分了解 TNLs 和信号伙伴的亚细胞定位要求，但它们的亚细胞定位要求尚未得到很好的理解。TNLs 表现出不同的亚细胞定位，而 EDS1 则表现出核质分布。在这里，我们研究了 TIR 和 EDS1 错误定位对不同 TNL 信号转导激活的影响。在 Nicotiana benthamiana 中，我们的结果表明，来自亚麻 L6 和拟南芥 RPS4 和 SNC1 TNLs 的 TIR 结构域的紧密接近从不同的细胞区室驱动信号转导激活。然而，在拟南芥中，Golgi 膜锚定的 L6 和核质分布的 RPS4 都需要 EDS1 的亚细胞定位。通过使用错误定位的 EDS1 变体，我们发现当 EDS1 存在于细胞质中时，自身免疫的 L6 和 RPS4 TIR 结构域可以诱导幼苗细胞死亡。然而，当 EDS1 被限制在细胞核内时，两者都会导致矮化表型，但不会导致细胞死亡。我们的数据指出了彻底研究 TNLs 和信号伙伴亚细胞定位动态以充分理解 TNL 信号转导的重要性。
