The Key Laboratory of Plant Immunity, Department of Plant Pathology, Nanjing Agricultural University, Nanjing, 210095, P. R. China.
Department of Botany and Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
EMBO J. 2024 Sep;43(17):3650-3676. doi: 10.1038/s44318-024-00174-6. Epub 2024 Jul 17.
Plant intracellular nucleotide-binding and leucine-rich repeat immune receptors (NLRs) play a key role in activating a strong pathogen defense response. Plant NLR proteins are tightly regulated and accumulate at very low levels in the absence of pathogen effectors. However, little is known about how this low level of NLR proteins is able to induce robust immune responses upon recognition of pathogen effectors. Here, we report that, in the absence of effector, the inactive form of the tomato NLR Sw-5b is targeted for ubiquitination by the E3 ligase SBP1. Interaction of SBP1 with Sw-5b via only its N-terminal domain leads to slow turnover. In contrast, in its auto-active state, Sw-5b is rapidly turned over as SBP1 is upregulated and interacts with both its N-terminal and NB-LRR domains. During infection with the tomato spotted wilt virus, the viral effector NSm interacts with Sw-5b and disrupts the interaction of Sw-5b with SBP1, thereby stabilizing the active Sw-5b and allowing it to induce a robust immune response.
植物细胞内核苷酸结合和富含亮氨酸重复的免疫受体（NLRs）在激活强烈的病原体防御反应中发挥关键作用。植物 NLR 蛋白受到严格调控，在没有病原体效应物的情况下，其积累水平非常低。然而，对于这种低水平的 NLR 蛋白如何在识别病原体效应物后能够引发强烈的免疫反应，人们知之甚少。在这里，我们报告说，在没有效应物的情况下，番茄 NLR Sw-5b 的无活性形式被 E3 连接酶 SBP1 靶向泛素化。SBP1 通过其仅有的 N 端结构域与 Sw-5b 相互作用，导致其缓慢周转。相比之下，在其自身激活状态下，Sw-5b 的周转率很快，因为 SBP1 上调并与它的 N 端和 NB-LRR 结构域相互作用。在感染番茄斑萎病毒时，病毒效应物 NSm 与 Sw-5b 相互作用并破坏 Sw-5b 与 SBP1 的相互作用，从而稳定活性 Sw-5b 并使其能够诱导强烈的免疫反应。
