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.

中文翻译：

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病毒效应子会阻止植物 NLR 受体的更新，从而触发强大的免疫反应。


植物细胞内核苷酸结合和富含亮氨酸的重复免疫受体（NLR）在激活强大的病原体防御反应中发挥着关键作用。在没有病原体效应子的情况下，植物 NLR 蛋白受到严格调控并以非常低的水平积累。然而，人们对这种低水平的 NLR 蛋白如何在识别病原体效应子后能够诱导强大的免疫反应知之甚少。在这里，我们报告，在没有效应子的情况下，番茄 NLR Sw-5b 的非活性形式被 E3 连接酶 SBP1 泛素化。 SBP1 仅通过其 N 端结构域与 Sw-5b 相互作用，导致周转缓慢。相比之下，在自动激活状态下，Sw-5b 会随着 SBP1 上调并与其 N 端和 NB-LRR 结构域相互作用而迅速翻转。在番茄斑萎病毒感染期间，病毒效应子 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 并使其诱导强大的免疫反应。