Melatonin (MT) is involved in various physiological processes and stress responses in animals and plants. However, little is known about the molecular mechanisms by which MT regulates potassium deficiency (DK) tolerance in crops. In this study, an appropriate concentration (50 μmol/L) was found to enhance the tolerance of wheat plants against DK. RNA‐seq analysis showed that a total of 6253 and 5873 differentially expressed genes (DEGs) were separately identified in root and leaf tissues of the DK + MT‐treated wheat plants. They functionally involved biological processes of secondary metabolite, signal transduction, and transport or catabolism. Of these, an upregulated high‐affinity K transporter 1 (TaHAK1) gene was next characterized. TaHAK1 overexpression markedly enhanced the K absorption, while its transient silencing exhibited the opposite effect, suggesting its important role in MT‐mediated DK tolerance. Moreover, yeast one‐hybrid (Y1H) was used to screen the upstream regulators of TaHAK1 gene and the transcription factor TaNAC71 was identified. The binding between TaNAC71 and TaHAK1 promoter was evidenced by using Y1H, LUC, and EMSA assays. Transient overexpression of TaNAC71 in wheat protoplasts activated the TaHAK1 expression, whereas its transient silencing inhibited the TaHAK1 expression and aggravated the sensitivity to DK. Exogenous MT application greatly upregulated the expression of TaHAK1 in both transient overexpression and silencing systems. Our findings revealed some molecular mechanisms underlying MT‐mediated DK tolerance and helped broaden its practical application in agriculture.

中文翻译：

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褪黑激素通过调控HAK1转运蛋白及其上游转录因子NAC71促进小麦缺钾耐受

褪黑激素 (MT) 参与动物和植物的各种生理过程和应激反应。然而，关于 MT 调节作物缺钾 (DK) 耐受性的分子机制知之甚少。在本研究中，发现适当的浓度（50 μmol/L）可以增强小麦植株对 DK 的耐受性。RNA-seq 分析表明，在 DK + MT 处理的小麦植株的根和叶组织中分别鉴定了 6253 和 5873 个差异表达基因（DEG）。它们在功能上涉及次级代谢物、信号转导和运输或分解代谢的生物过程。其中，接下来表征了上调的高亲和力 K 转运蛋白 1 ( TaHAK1 ) 基因。塔哈克1过表达显着增强了 K 吸收，而其瞬时沉默表现出相反的效果，表明其在 MT 介导的 DK 耐受中起重要作用。此外，酵母单杂交（Y1H）用于筛选TaHAK1基因的上游调节因子，并鉴定出转录因子 TaNAC71。TaNAC71 和TaHAK1启动子之间的结合通过使用 Y1H、LUC 和 EMSA 检测得到证实。TaNAC71在小麦原生质体中的瞬时过表达激活了TaHAK1 的表达，而其瞬时沉默抑制了TaHAK1 的表达并加重了对 DK 的敏感性。外源MT应用大大上调TaHAK1的表达在瞬时过表达和沉默系统中。我们的研究结果揭示了 MT 介导的 DK 耐受性的一些分子机制，并有助于扩大其在农业中的实际应用。