State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, 271018, Shandong, People's Republic of China.
Plant Cell Rep. 2021 Nov;40(11):2135-2150. doi: 10.1007/s00299-020-02590-4. Epub 2020 Sep 5.
We report that GhWRKY21, a WRKY transcription factor, plays essential roles in regulating the intensity of the drought-induced ABA signalling pathway by facilitating the expression of GhHAB in cotton (Gossypium hirsutum). Abscisic acid (ABA) is one of the most important plant hormones in response to abiotic stress. However, activation of the ABA signalling pathway often leads to growth inhibition. The mechanisms that regulate the intensity of ABA signals are poorly understood. Here, we isolated and analysed the cotton group IId WRKY transcription factor (TF) gene GhWRKY21. Functional analysis indicated that GhWRKY21 plays a negative role in the drought response of cotton. Silencing of GhWRKY21 in cotton dramatically increased drought tolerance, whereas ectopic GhWRKY21 overexpression in Nicotiana benthamiana decreased drought tolerance. Furthermore, the GhWRKY21-mediated drought tolerance was ABA dependent. To clarify the mechanism underlying the GhWRKY21-mediated regulation of drought tolerance, 17 clade-A-type type 2C protein phosphatase (PP2C) genes, which are negative regulators of ABA signalling, were identified in cotton. Notably, GhWRKY21 interacted specifically with the W-box element within the promoter of GhHAB and regulated its expression. Silencing of GhHAB in cotton yielded a phenotype similar to that of GhWRKY21-silenced cotton. These results suggest that GhWRKY21 regulates the intensity of ABA signals by facilitating the expression of GhHAB. In summary, these findings dramatically improve our understanding of the function of WRKY TFs and provide insights into the mechanism of ABA-mediated drought tolerance.
我们报告称，WRKY 转录因子 GhWRKY21 通过促进棉花（Gossypium hirsutum）GhHAB 的表达，在调节干旱诱导的 ABA 信号通路强度方面发挥着重要作用。脱落酸（ABA）是植物应对非生物胁迫的最重要激素之一。然而，ABA 信号通路的激活往往会导致生长抑制。调节 ABA 信号强度的机制尚不清楚。在这里，我们分离并分析了棉花第 IId WRKY 转录因子（TF）基因 GhWRKY21。功能分析表明，GhWRKY21 在棉花的干旱响应中发挥负调控作用。棉花中 GhWRKY21 的沉默显著提高了耐旱性，而拟南芥中 GhWRKY21 的异位过表达则降低了耐旱性。此外，GhWRKY21 介导的耐旱性依赖于 ABA。为了阐明 GhWRKY21 介导的耐旱性调控的机制，我们在棉花中鉴定了 17 个 clade-A 型 2C 蛋白磷酸酶（PP2C）基因，这些基因是 ABA 信号的负调控因子。值得注意的是，GhWRKY21 与 GhHAB 启动子中的 W 框元件特异性相互作用并调节其表达。棉花中 GhHAB 的沉默产生了类似于 GhWRKY21 沉默棉花的表型。这些结果表明，GhWRKY21 通过促进 GhHAB 的表达来调节 ABA 信号的强度。总之，这些发现极大地提高了我们对 WRKY TF 功能的理解，并为 ABA 介导的耐旱性机制提供了新的见解。
