SummaryThe abscisic acid (ABA) signalling pathway plays a crucial role in plants’ response to drought stress. In this study, we aimed to characterize the impact of an ABA signalling module, which consisted of TaPYL9 and its downstream partners in Triticum aestivum, on plant drought adaptation. Our results showed that TaPYL9 protein contains conserved motifs and targets plasma membrane and nucleus after being sorted by the endoplasmic reticulum. In addition, TaPYL9 transcripts in both roots and leaves were significantly upregulated in response to drought stress. We conducted glucuronidase (GUS) histochemical staining analysis for transgenic plants carrying a truncated TaPYL9 promoter, which suggested that cis‐elements associate with ABA and drought response, such as ABRE, DRE and recognition sites MYB and MYC, regulating the gene transcription under drought conditions. Using protein interaction assays (i.e., yeast two‐hybrid, bimolecular fluorescence complementation (BiFC), co‐immunoprecipitation (Co‐IP) and in vitro pull‐down), we demonstrated interactions between the intermediate segment of TaPYL9, the intermediate segment of TaPP2C6, the N‐terminus of TaSnRK2.8 and the C‐terminus of the transcription factor TabZIP1 in wheat, indicating the involvement of TaPYL9 in the constitution of an ABA signalling module, namely TaPYL9/TaPP2C6/TaSnRK2.8/TabZIP1. Transgene analysis revealed that TaPYL9, TaSnRK2.8 and TabZIP1 positively regulated drought response, while TaPP2C6 negatively regulated it, and that these genes were closely associated with the regulation of stomata movement, osmolyte accumulation and ROS homeostasis. Electrophoretic mobility shift (EMSA) and transcriptioal activation assays indicated that TabZIP1 interacted promoters of TaP5CS2, TaSLAC1‐1 and TaCAT2 and activated transcription of these genes, which regulated proline biosynthesis, stomata movement and ROS scavenging upon drought signalling, respectively. Furthermore, we found that the transcripts of TaPYL9 and stress‐responsive genes were positively correlated with yields in wheat cultivars under field drought conditions. Altogether, our findings suggest that the TaPYL9‐involved signalling pathway significantly regulates drought response by modulating osmotic stress‐associated physiological processes in T. aestivum.

中文翻译：

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小麦 TaPYL9 相关的信号通路通过调节不同的渗透胁迫相关生理指标影响植物干旱响应


摘要脱落酸 （ABA） 信号通路在植物对干旱胁迫的反应中起着至关重要的作用。在这项研究中，我们旨在表征 ABA 信号模块（由 TaPYL9 及其在 Triticum aestivum 中的下游伙伴组成）对植物干旱适应的影响。我们的结果表明，TaPYL9 蛋白在经内质网分选后包含保守基序并靶向质膜和细胞核。此外，根和叶中的 TaPYL9 转录本在干旱胁迫下均显著上调。我们对携带截短 TaPYL9 启动子的转基因植物进行了葡糖醛酸酶 （GUS） 组织化学染色分析，结果表明顺式元件与 ABA 和干旱响应相关，如 ABRE 、 DRE 和识别位点 MYB 和 MYC，调节干旱条件下的基因转录。使用蛋白质相互作用测定（即酵母双杂交、双分子荧光互补 （BiFC）、免疫共沉淀 （Co-IP） 和体外下拉），我们证明了小麦中 TaPYL9 的中间片段、TaPP2C6 的中间片段、TaSnRK2.8 的 N 端和转录因子 TabZIP1 的 C 端之间的相互作用，表明 TaPYL9 参与 ABA 信号模块的构成， 即 TaPYL9/TaPP2C6/TaSnRK2.8/TabZIP1。转基因分析显示，TaPYL9、TaSnRK2.8 和 TabZIP1 正向调节干旱响应，而 TaPP2C6 负向调节干旱响应，这些基因与气孔运动、渗透液积累和 ROS 稳态的调节密切相关。 电泳迁移率变化 （EMSA） 和转录激活试验表明，TabZIP1 与 TaP5CS2 、 TaSLAC1-1 和 TaCAT2 的启动子相互作用，并激活这些基因的转录，分别调节脯氨酸生物合成、气孔运动和 ROS 清除干旱信号。此外，我们发现在田间干旱条件下，TaPYL9 和胁迫响应基因的转录本与小麦品种的产量呈正相关。总而言之，我们的研究结果表明，TaPYL9 相关的信号通路通过调节 T. aestivum 中与渗透胁迫相关的生理过程来显着调节干旱反应。