Genetics, Development and Cell Biology Department, Plant Sciences Institute, Iowa State University, 1111 WOI Road, Ames, Iowa, USA.
Plant Cell Environ. 2021 Aug;44(8):2625-2635. doi: 10.1111/pce.14063. Epub 2021 May 2.
The unfolded protein response (UPR) in plants is elicited by endoplasmic reticulum stress, which can be brought about by adverse environmental conditions. The response is mediated by a conserved signalling network composed of two branches - one branch involving inositol requiring enzyme1- basic leucine zipper60 (IRE1-bZIP60) signalling pathway and another branch involving the membrane transcription factors, bZIP17 and -28. The UPR has been reported in Chlamydomonas reinhardtii, a unicellular green alga, which lacks some canonical UPR signalling components found in vascular plants, raising the question whether C. reinhardtii uses other means such as oxidative signalling or Regulated IRE1-Dependent Decay to activate the UPR. In vascular plants, IRE1 splices bZIP60 mRNA in response to endoplasmic reticulum stress by cutting at a site in the RNA that is highly conserved in structure and sequence. Monocots have a single IRE1 gene required for viability in rice, while dicots have two IRE1 genes, IRE1a and -b. Brassicas have a third IRE1 gene, IRE1c, which lacks a lumenal domain, but is required in combination with IRE1b for gametogenesis. Vascular and non-vascular plants upregulate a similar set of genes in response to endoplasmic reticulum stress despite differences in the complexity of their UPR signalling networks.
植物中的未折叠蛋白反应（UPR）是由内质网应激引起的，这种应激可能是由不利的环境条件引起的。该反应由一个保守的信号网络介导，该网络由两个分支组成——一个分支涉及肌醇需要酶 1-碱性亮氨酸拉链 60（IRE1-bZIP60）信号通路，另一个分支涉及膜转录因子 bZIP17 和 -28。未折叠蛋白反应已在单细胞绿藻莱茵衣藻中报道，该藻类缺乏一些在维管植物中发现的典型 UPR 信号成分，这引发了一个问题，即莱茵衣藻是否使用其他方法，如氧化信号或调节 IRE1 依赖性衰减来激活 UPR。在维管植物中，IRE1 在响应内质网应激时通过在 RNA 中高度保守的结构和序列位点切割来剪接 bZIP60 mRNA。单子叶植物在水稻中需要一个 IRE1 基因才能存活，而双子叶植物则有两个 IRE1 基因，IRE1a 和 -b。芸薹属植物有第三个 IRE1 基因 IRE1c，它缺乏内腔域，但与 IRE1b 结合对于配子发生是必需的。尽管 UPR 信号网络的复杂性不同，但血管植物和非血管植物在响应内质网应激时都会上调一组相似的基因。
