Li Yi-Hua, Ke Tai-Yu, Shih Wei-Che, Liou Ruey-Fen, Wang Chao-Wen
Department of Plant Pathology and Microbiology, National Taiwan University, Taipei, Taiwan.
Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan.
Front Plant Sci. 2021 Sep 1;12:721548. doi: 10.3389/fpls.2021.721548. eCollection 2021.
The receptor-like kinase Suppressor of BIR1 (SOBIR1) binds various receptor-like proteins (RLPs) that perceive microbe-associated molecular patterns (MAMPs) at the plasma membrane, which is thought to activate plant pattern-triggered immunity (PTI) against pathogen invasion. Despite its potentially crucial role, how SOBIR1 transmits immune signaling to ultimately elicit PTI remains largely unresolved. Herein, we report that a gene RLP1, like SOBIR1, was highly induced upon infection. Intriguingly, RLP1 is characterized as a receptor-like protein localizing to the endoplasmic reticulum (ER) membrane rather than the plasma membrane. Using bimolecular fluorescence complementation and affinity purification assays, we established that RLP1 is likely to associate with SOBIR1 through the contact between the ER and plasma membrane. We further found that SOBIR1 at the plasma membrane partitions into mobile microdomains that undergo frequent lateral movement and internalization. Remarkably, the dynamics of SOBIR1 microdomain is coupled to the remodeling of the cortical ER network. When SOBIR1 microdomains were induced by the MAMP ParA1, tobacco cells overexpressing RLP1 accelerated SOBIR1 internalization. Overexpressing RLP1 in tobacco further exaggerated the ParA1-induced necrosis. Together, these findings have prompted us to propose that ER and the ER-localized RLP1 may play a role in transmitting plant immune signals by regulating SOBIR1 internalization.
类受体激酶BIR1抑制因子（SOBIR1）与多种类受体蛋白（RLP）结合，这些类受体蛋白在质膜上感知微生物相关分子模式（MAMP），这被认为可激活植物针对病原体入侵的模式触发免疫（PTI）。尽管其可能具有关键作用，但SOBIR1如何传递免疫信号以最终引发PTI在很大程度上仍未得到解决。在此，我们报道一个基因RLP1，与SOBIR1一样，在感染后被高度诱导。有趣的是，RLP1被表征为一种定位于内质网（ER）膜而非质膜的类受体蛋白。通过双分子荧光互补和亲和纯化分析，我们确定RLP1可能通过内质网与质膜之间的接触与SOBIR1相互作用。我们进一步发现质膜上的SOBIR1会分隔到经历频繁侧向移动和内化的可移动微结构域中。值得注意的是，SOBIR1微结构域的动态变化与皮质内质网网络的重塑相关联。当SOBIR1微结构域由MAMP ParA1诱导时，过表达RLP1的烟草细胞加速了SOBIR1的内化。在烟草中过表达RLP1进一步加剧了ParA1诱导的坏死。总之，这些发现促使我们提出内质网和内质网定位的RLP1可能通过调节SOBIR1的内化在传递植物免疫信号中发挥作用。
