State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, 100193, China.
Crop Research Institute of Tianjin Academy of Agricultural Sciences, Tianjin, 300384, China.
Plant J. 2019 May;98(4):680-696. doi: 10.1111/tpj.14265. Epub 2019 Mar 6.
Recent studies on E3 of endoplasmic reticulum (ER)-associated degradation (ERAD) in plants have revealed homologs in yeast and animals. However, it remains unknown whether the plant ERAD system contains a plant-specific E3 ligase. Here, we report that MfSTMIR, which encodes an ER-membrane-localized RING E3 ligase that is highly conserved in leguminous plants, plays essential roles in the response of ER and salt stress in Medicago. MfSTMIR expression was induced by salt and tunicamycin (Tm). mtstmir loss-of-function mutants displayed impaired induction of the ER stress-responsive genes BiP1/2 and BiP3 under Tm treatment and sensitivity to salt stress. MfSTMIR promoted the degradation of a known ERAD substrate, CPY*. MfSTMIR interacted with the ERAD-associated ubiquitin-conjugating enzyme MtUBC32 and Sec61-translocon subunit MtSec61γ. MfSTMIR did not affect MtSec61γ protein stability. Our results suggest that the plant-specific E3 ligase MfSTMIR participates in the ERAD pathway by interacting with MtUBC32 and MtSec61γ to relieve ER stress during salt stress.
最近对植物内质网（ER）相关降解（ERAD）E3 的研究揭示了酵母和动物中的同源物。然而，尚不清楚植物 ERAD 系统是否包含植物特异性 E3 连接酶。在这里，我们报告说，MfSTMIR 编码一种在豆科植物中高度保守的 ER 膜定位的 RING E3 连接酶，它在 Medicago 中对 ER 和盐胁迫的反应中起着重要作用。MfSTMIR 的表达受到盐和衣霉素（Tm）的诱导。mtstmir 功能丧失突变体在 Tm 处理下 BiP1/2 和 BiP3 等 ER 应激反应基因的诱导受损，对盐胁迫敏感。MfSTMIR 促进了已知的 ERAD 底物 CPY*的降解。MfSTMIR 与 ERAD 相关的泛素连接酶 MtUBC32 和 Sec61 易位亚基 MtSec61γ 相互作用。MfSTMIR 不影响 MtSec61γ 蛋白的稳定性。我们的结果表明，植物特异性 E3 连接酶 MfSTMIR 通过与 MtUBC32 和 MtSec61γ 相互作用参与 ERAD 途径，以在盐胁迫期间缓解 ER 应激。
