Division of Applied Life Sciences (BK21+) and Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju, 52828, Korea.
Department of Biomedical Science and Engineering, Konkuk University, Seoul, 05029, Korea.
New Phytol. 2018 Oct;220(1):163-177. doi: 10.1111/nph.15279. Epub 2018 Jun 22.
Investigation of the endoplasmic reticulum-associated degradation (ERAD) system in plants led to the identification of ERAD-mediating RING finger protein (EMR) as a plant-specific ERAD E3 ligase from Arabidopsis. EMR was significantly up-regulated under endoplasmic reticulum (ER) stress conditions. The EMR protein purified from bacteria displayed high E3 ligase activity, and tobacco leaf-produced EMR mediated mildew resistance locus O-12 (MLO12) degradation in a proteasome-dependent manner. Subcellular localization and coimmunoprecipitation analyses showed that EMR forms a complex with ubiquitin-conjugating enzyme 32 (UBC32) as a cytosolic interaction partner. Mutation of EMR and RNA interference (RNAi) increased the tolerance of plants to ER stress. EMR RNAi in the bri1-5 background led to partial recovery of the brassinosteroid (BR)-insensitive phenotypes as compared with the original mutant plants and increased ER stress tolerance. The presented results suggest that EMR is involved in the plant ERAD system that affects BR signaling under ER stress conditions as a novel Arabidopsis ring finger E3 ligase mainly present in cytosol while the previously identified ERAD E3 components are typically membrane-bound proteins.
对植物内质网相关降解（ERAD）系统的研究导致了 ERAD 介导的 RING 指蛋白（EMR）的鉴定，它是一种来自拟南芥的植物特异性 ERAD E3 连接酶。在内质网（ER）应激条件下，EMR 显著上调。从细菌中纯化的 EMR 蛋白显示出高 E3 连接酶活性，并且烟草叶产生的 EMR 以依赖蛋白酶体的方式介导白粉病抗性位点 O-12（MLO12）降解。亚细胞定位和共免疫沉淀分析表明，EMR 与泛素结合酶 32（UBC32）形成复合物，作为细胞质相互作用伙伴。EMR 的突变和 RNA 干扰（RNAi）增加了植物对 ER 应激的耐受性。与原始突变体植物相比，在 bri1-5 背景下的 EMR RNAi 导致油菜素内酯（BR）不敏感表型的部分恢复，并增加了 ER 应激耐受性。研究结果表明，EMR 参与植物 ERAD 系统，该系统作为一种新型拟南芥环指 E3 连接酶，在 ER 应激条件下影响 BR 信号转导，主要存在于细胞质中，而先前鉴定的 ERAD E3 成分通常是膜结合蛋白。
