Unfolded protein-independent IRE1 activation contributes to multifaceted developmental processes in Arabidopsis
Unfolded protein-independent IRE1 activation contributes to multifaceted developmental processes in Arabidopsis
复制标题
DOI：
10.26508/lsa.201900459
复制
发表时间：
2019-10-01
影响因子：
4.4
通讯作者：
Koizumi, Nozomu
中科院分区：
文献类型：
--
作者：
Mishiba, Kei-ichiro;Iwata, Yuji;Koizumi, Nozomu
在拟南芥中，IRE1A和IRE1B双突变体（ire1a/b）无法激活bZIP60 mRNA的细胞质剪接并在内质网应激下调节IRE1依赖性衰退，而突变体在正常条件下不会表现出严重的发育缺陷。在这项研究中，我们重点关注拟南芥 IRE1C 基因，其产物缺乏传感器结构域。我们发现ire1a/b/c三重突变体是致命的，并且ire1a/b突变体中的杂合IRE1C（ire1c/）突变导致生长缺陷和花粉粒数量减少。遗传分析表明，在 ire1a/b 突变背景下，IRE1C 是雄配子体发育所必需的。缺乏管腔传感器结构域 (ALB) 的 IRE1B 突变体的表达补充了 ire1a/b/c 单倍型中雄性配子体的发育缺陷。在体内，ALE 蛋白通过甘油处理被激活，甘油处理增加了饱和脂质的组成，并且能够激活受调节的 IRE1 依赖性衰变，但不能激活 bZ1P60 剪接。这些观察结果表明，IRE1 使用绕过未折叠的蛋白质感应管腔结构域的替代激活机制，有助于植物发育，尤其是雄性配子发生。
In Arabidopsis, the IRE1A and IRE1B double mutant (ire1a/b) is unable to activate cytoplasmic splicing of bZIP60 mRNA and regulated IRE1-dependent decay under ER stress, whereas the mutant does not exhibit severe developmental defects under normal conditions. In this study, we focused on the Arabidopsis IRE1C gene, whose product lacks a sensor domain. We found that the ire1a/b/c triple mutant is lethal, and heterozygous IRE1C (ire1c/) mutation in the ire1a/b mutants resulted in growth defects and reduction of the number of pollen grains. Genetic analysis revealed that IRE1C is required for male gametophyte development in the ire1a/b mutant background. Expression of a mutant form of IRE1B that lacks the luminal sensor domain (ALB) complemented a developmental defect in the male gametophyte in ire1a/b/c haplotype. In vivo, the ALE , protein was activated by glycerol treatment that increases the composition of saturated lipid and was able to activate regulated IRE1-dependent decay but not bZ1P60 splicing. These observations suggest that IRE1 contributes to plant development, especially male gametogenesis, using an alternative activation mechanism that bypasses the unfolded protein-sensing luminal domain.