Introduction

Drought is the principal abiotic stress that severely impacts cotton (Gossypium hirsutum) growth and productivity. Upon sensing drought, plants activate stress-related signal transduction pathways, including ABA signal and mitogen-activated protein kinase (MAPK) cascade. However, as the key components with the fewest members in the MAPK cascade, the function and regulation of GhMKKs need to be elucidated. In addition, the relationship between MAPK module and the ABA core signaling pathway remains incompletely understood.

Objective

Here we aim to elucidate the molecular mechanism of cotton response to drought, with a focus on mitogen-activated protein kinase (MAPK) cascades activating ABA signaling.

Methods

Biochemical, molecular and genetic analysis were used to study the GhMAP3K62-GhMKK16-GhMPK32-GhEDT1 pathway genes.

Results

A nucleus- and membrane-localized MAPK cascade pathway GhMAP3K62-GhMKK16-GhMPK32, which targets and phosphorylates the nuclear-localized transcription factor GhEDT1, to activate downstream GhNCED3 to mediate ABA-induced stomatal closure and drought response was characterized in cotton. Overexpression of GhMKK16 promotes ABA accumulation, and enhances drought tolerance via regulating stomatal closure under drought stress. Conversely, RNAi-mediated knockdown of GhMKK16 expression inhibits ABA accumulation, and reduces drought tolerance. Virus-induced gene silencing (VIGS)-mediated knockdown of either GhMAP3K62, GhMPK32 or GhEDT1 expression represses ABA accumulation and reduces drought tolerance through inhibiting stomatal closure. Expression knockdown of GhMPK32 or GhEDT1 in GhMKK16-overexpressing cotton reinstates ABA content and stomatal opening-dependent drought sensitivity to wild type levels. GhEDT1 could bind to the HD boxes in the promoter of GhNCED3 to activate its expression, resulting in ABA accumulation. We propose that the MAPK cascade GhMAP3K62-GhMKK16-GhMPK32 pathway functions on drought response through ABA-dependent stomatal movement in cotton.

中文翻译：

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GhMAP3K62-GhMKK16-GhMPK32 激酶级联通过激活 GhEDT1 介导的 ABA 积累来调节棉花的耐旱性

介绍

干旱是严重影响棉花（ Gossypium hirsutum）生长和生产力的主要非生物胁迫。感知到干旱后，植物会激活与胁迫相关的信号转导途径，包括 ABA 信号和丝裂原激活蛋白激酶 (MAPK) 级联。然而，作为 MAPK 级联中成员最少的关键元件， GhMKK的功能和调控仍需阐明。此外，MAPK模块与ABA核心信号通路之间的关系仍不完全清楚。

客观的

在这里，我们的目标是阐明棉花响应干旱的分子机制，重点关注丝裂原激活蛋白激酶 (MAPK) 级联激活 ABA 信号传导。

方法

采用生化、分子和遗传分析来研究 GhMAP3K62-GhMKK16-GhMPK32-GhEDT1 通路基因。

结果

棉花中的核定位和膜定位 MAPK 级联途径 GhMAP3K62-GhMKK16-GhMPK32 靶向并磷酸化核定位转录因子 GhEDT1，激活下游GhNCED3 ，介导 ABA 诱导的气孔关闭和干旱响应。GhMKK16的过度表达促进 ABA 积累，并通过在干旱胁迫下调节气孔关闭来增强耐旱性。相反，RNAi 介导的GhMKK16表达敲低会抑制 ABA 积累，并降低耐旱性。病毒诱导的基因沉默 (VIGS) 介导的GhMAP3K62、GhMPK32或GhEDT1表达敲低可抑制 ABA 积累，并通过抑制气孔关闭来降低耐旱性。过表达GhMKK16的棉花中GhMPK32或GhEDT1的表达敲低可恢复 ABA 含量和气孔开放依赖性干旱敏感性至野生型水平。GhEDT1 可以与GhNCED3启动子中的 HD 盒结合，激活其表达，导致 ABA 积累。我们提出 MAPK 级联 GhMAP3K62-GhMKK16-GhMPK32 途径通过棉花中依赖于 ABA 的气孔运动来发挥干旱响应作用。