Protein kinase and ribonuclease domains of IRE1 confer stress tolerance, vegetative growth, and reproductive development in Arabidopsis
Protein kinase and ribonuclease domains of IRE1 confer stress tolerance, vegetative growth, and reproductive development in Arabidopsis
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DOI：
10.1073/pnas.1314749110
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发表时间：
2013-11-26
影响因子：
11.1
通讯作者：
Howell, Stephen H.
中科院分区：
文献类型：
--
作者：
Deng, Yan;Srivastava, Renu;Howell, Stephen H.
未折叠蛋白质反应（unfolded protein response，UPR）赋予植物感知、响应和保护自身免受不利环境条件影响的能力。拟南芥中的UPR信号通路有两个“臂”，一个臂涉及双功能蛋白激酶（PK）/核糖核酸酶，IRE 1，一种RNA剪接酶，另一个臂涉及膜相关转录因子，如碱性亮氨酸拉链转录因子28（bZIP 28）。由于功能冗余，植物UPR信号通路中的单基因突变通常不会导致突出的表型。在这项研究中，我们在UPR信号通路中产生了多个突变，例如ire 1a ire 1b双突变体，它在胁迫耐受性和营养生长发育方面表现出缺陷。IRE 1a IRE 1b与IRE 1b的PK或RNase结构域中含有位点特异性突变的构建体互补表明，功能性RNase结构域是内质网应激耐受所需的，并且PK和RNase结构域都是非应激条件下正常营养生长所需的。胁迫条件下的根生长依赖于IRE 1b，bZIP 60 mRNA的剪接靶，并调节IRE 1依赖的靶基因的衰减。然而，根和芽的生长在没有压力是独立的bZIP 60。在三重ire 1a ire 1b bzip 28突变体中阻断UPR信号通路的双臂是致命的，在非胁迫条件下影响花粉生活力。与IRE 1b构建体的互补表明PK和RNase结构域都是正常配子体发育所需的，但bZIP 60不是。因此，UPR在植物的胁迫耐受性以及正常营养生长和生殖发育中起着关键作用。
The unfolded protein response (UPR) endows plants with the capacity to perceive, respond, and protect themselves from adverse environmental conditions. The UPR signaling pathway in Arabidopsis has two "arms," one arm involving the bifunctional protein kinase (PK)/ribonuclease, IRE1, a RNA splicing enzyme, and another involving membrane-associated transcription factors, such as basic leucine zipper transcription factor 28 (bZIP28). Because of functional redundancies, single gene mutations in the plant UPR signaling pathway generally have not resulted in prominent phenotypes. In this study we generated multiple mutations in the UPR signaling pathway, such as an ire1a ire1b double mutant, which showed defects in stress tolerance and vegetative growth and development. Complementation of ire1a ire1b with constructs containing site-specific mutations in the PK or RNase domains of IRE1b demonstrated that a functional RNase domain is required for endoplasmic reticulum stress tolerance, and that both the PK and RNase domains are required for normal vegetative growth under unstressed conditions. Root growth under stress conditions was dependent on the splicing target of IRE1b, bZIP60 mRNA, and on regulated IRE1-dependent decay of target genes. However, root and shoot growth in the absence of stress was independent of bZIP60. Blocking both arms of the UPR signaling pathway in a triple ire1a ire1b bzip28 mutant was lethal, impacting pollen viability under unstressed conditions. Complementation with IRE1b constructs showed that both the PK and RNase domains are required for normal gametophyte development, but bZIP60 is not. Hence, the UPR plays a critical role in stress tolerance, and in normal vegetative growth and reproductive development in plants.