Our previous study demonstrated that the expression of GhNAC4, a NAC transcription factor from cotton, was induced by abiotic stresses and abscisic acid (ABA). In the present study, we investigated the molecular mechanisms underlying ABA and stress response of GhNAC4. Overexpression of GhNAC4 in transgenic tobacco conferred tolerance to salinity and drought treatments with associated enhanced expression of several stress-responsive marker genes. GhNAC4 is a protein that is translocated to the nucleus where it exhibits transcriptional activation property and also forms homo-dimers. In this study, we also investigated the domains essential for the biochemical functions of GhNAC4. We developed transgenic tobacco plants overexpressing the GhNAC4 NAC-domain and the transcriptional regulatory (TR) domain separately. NAC-domain transgenics showed hypersensitivity to exogenous ABA while TR-domain transgenics exhibited reduced sensitivity. Abiotic stress assays indicated that transgenic plants expressing both the domains separately were more tolerant than wild type plants with the NAC-domain transgenics showing increased tolerance as compared to TR-domain transgenics. Expression analysis revealed that various stress-responsive genes were upregulated in both NAC-domain and TR-domain transgenics under salinity and drought treatments. These results suggest that the stress tolerance ability of GhNAC4 is associated with both the component domains while the ABA responsiveness is largely associated with N-terminal NAC-domain.

中文翻译：

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陆地棉 NAC 转录因子 GhNAC4 与 ABA 和非生物胁迫反应的结构-功能关系


我们之前的研究表明，GhNAC4（一种来自棉花的 NAC 转录因子）的表达是由非生物胁迫和脱落酸 (ABA) 诱导的。在本研究中，我们研究了 ABA 和 GhNAC4 应激反应的分子机制。转基因烟草中 GhNAC4 的过度表达赋予了对盐度和干旱处理的耐受性，并增强了几种胁迫响应标记基因的表达。 GhNAC4 是一种易位至细胞核的蛋白质，在细胞核中表现出转录激活特性并形成同源二聚体。在这项研究中，我们还研究了 GhNAC4 生化功能所必需的结构域。我们开发了分别过表达 GhNAC4 NAC 结构域和转录调节 (TR) 结构域的转基因烟草植物。 NAC 结构域转基因对外源 ABA 表现出超敏感性，而 TR 结构域转基因则表现出敏感性降低。非生物胁迫测定表明，分别表达两个结构域的转基因植物比野生型植物更具耐受性，其中NAC结构域转基因植物与TR结构域转基因植物相比显示出增强的耐受性。表达分析表明，在盐度和干旱处理下，NAC 结构域和 TR 结构域转基因中的各种胁迫响应基因均上调。这些结果表明，GhNAC4 的应激耐受能力与两个组成域相关，而 ABA 响应性很大程度上与 N 端 NAC 域相关。