State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China.
State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, China.
Plant Biotechnol J. 2020 May;18(5):1317-1329. doi: 10.1111/pbi.13297. Epub 2019 Dec 6.
Heat stress induces misfolded protein accumulation in endoplasmic reticulum (ER), which initiates the unfolded protein response (UPR) in plants. Previous work has demonstrated the important role of a rice ER membrane-associated transcription factor OsbZIP74 (also known as OsbZIP50) in UPR. However, how OsbZIP74 and other membrane-associated transcription factors are involved in heat stress tolerance in rice is not reported. In the current study, we discovered that OsNTL3 is required for heat stress tolerance in rice. OsNTL3 is constitutively expressed and up-regulated by heat and ER stresses. OsNTL3 encodes a NAC transcription factor with a predicted C-terminal transmembrane domain. GFP-OsNTL3 relocates from plasma membrane to nucleus in response to heat stress and ER stress inducers. Loss-of-function mutation of OsNTL3 confers heat sensitivity while inducible expression of the truncated form of OsNTL3 without the transmembrane domain increases heat tolerance in rice seedlings. RNA-Seq analysis revealed that OsNTL3 regulates the expression of genes involved in ER protein folding and other processes. Interestingly, OsNTL3 directly binds to OsbZIP74 promoter and regulates its expression in response to heat stress. In turn, up-regulation of OsNTL3 by heat stress is dependent on OsbZIP74. Thus, our work reveals the important role of OsNTL3 in thermotolerance, and a regulatory circuit mediated by OsbZIP74 and OsNTL3 in communications among ER, plasma membrane and nucleus under heat stress conditions.
热应激会导致内质网（ER）中错误折叠的蛋白质积累，从而引发植物 unfolded protein response（UPR）。先前的研究表明，水稻内质网膜相关转录因子 OsbZIP74（也称为 OsbZIP50）在 UPR 中起重要作用。然而，OsbZIP74 和其他膜相关转录因子如何参与水稻的耐热性尚未报道。在本研究中，我们发现 OsNTL3 是水稻耐热所必需的。OsNTL3 组成型表达，并受热和 ER 应激诱导而上调。OsNTL3 编码一个具有预测的 C 端跨膜结构域的 NAC 转录因子。GFP-OsNTL3 在响应热应激和 ER 应激诱导剂时从质膜重新定位到细胞核。OsNTL3 的功能丧失突变赋予其对热的敏感性，而无跨膜结构域的截短形式的 OsNTL3 的诱导表达增加了水稻幼苗的耐热性。RNA-Seq 分析表明，OsNTL3 调节参与 ER 蛋白折叠和其他过程的基因的表达。有趣的是，OsNTL3 直接结合 OsbZIP74 启动子，并在响应热应激时调节其表达。反过来，热应激上调 OsNTL3 依赖于 OsbZIP74。因此，我们的工作揭示了 OsNTL3 在耐热性中的重要作用，以及在热应激条件下由 OsbZIP74 和 OsNTL3 介导的 ER、质膜和细胞核之间通讯的调节回路。
