N⁶-methyladenosine (m⁶A) is the most prevalent internal modification present in mRNAs, and is considered to participate in a range of developmental and biological processes. Drought response is highly regulated at the genomic, transcriptional and post-transcriptional levels. However, the biological function and regulatory mechanism of m⁶A modification in the drought stress response is still poorly understood. We generated a transcriptome-wide m⁶A map using drought-resistant and drought-sensitive varieties of cotton under different water deficient conditions to uncover patterns of m⁶A methylation in cotton response to drought stress. The results reveal that m⁶A represents a common modification and exhibit dramatic changes in distribution during drought stress. More 5'UTR m⁶A was deposited in the drought-resistant variety and was associated with a positive effect on drought resistance by regulating mRNA abundance. Interestingly, we observed that increased m⁶A abundance was associated with increased mRNA abundance under drought, contributing to drought resistance, and vice versa. The demethylase GhALKBH10B was found to decrease m⁶A levels, facilitating the mRNA decay of ABA signal-related genes (GhZEP, GhNCED4 and GhPP2CA) and Ca²⁺ signal-related genes (GhECA1, GhCNGC4, GhANN1 and GhCML13), and mutation of GhALKBH10B enhanced drought resistance at seedling stage in cotton. Virus-induced gene silencing (VIGS) of two Ca²⁺-related genes, GhECA1 and GhCNGC4, reduced drought resistance with the decreased m⁶A enrichment on silenced genes in cotton. Collectively, we reveal a novel mechanism of post-transcriptional modification involved in affecting drought response in cotton, by mediating m⁶A methylation on targeted transcripts in the ABA and Ca²⁺ signalling transduction pathways.

中文翻译：

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N6-甲基腺苷 RNA 修饰以 Ca2+ 和 ABA 依赖性方式调节棉花干旱反应

N ⁶ -甲基腺苷 (m ⁶ A) 是 mRNA 中最普遍的内部修饰，被认为参与一系列发育和生物学过程。干旱反应在基因组、转录和转录后水平受到高度调控。^{然而，m 6} A修饰在干旱胁迫响应中的生物学功能和调控机制仍知之甚少。我们使用不同缺水条件下的抗旱和干旱敏感棉花品种生成了转录组范围的 m ⁶ A 图谱，以揭示棉花对干旱胁迫反应中m ^{6 A 甲基化的模式。}结果表明，m ⁶A 代表一种常见的修饰，并在干旱胁迫期间表现出分布的显着变化。更多的 5'UTR m ⁶ A 沉积在抗旱品种中，并通过调节 mRNA 丰度对抗旱性产生积极影响。有趣的是，我们观察到 m ⁶ A 丰度增加与干旱条件下 mRNA 丰度增加相关，有助于抗旱，反之亦然。发现去甲基化酶 GhALKBH10B 可降低 m ⁶ A 水平，促进 ABA 信号相关基因（GhZEP、GhNCED4和GhPP2CA）和 Ca ²⁺信号相关基因（GhECA1、GhCNGC4）的 mRNA 衰变, GhANN1和GhCML13 ), 以及GhALKBH10B的突变增强了棉花苗期的抗旱性。^{两个 Ca 2+}相关基因GhECA1和GhCNGC4的病毒诱导基因沉默 (VIGS)随着棉花沉默基因上m ⁶ A 富集的减少而降低了抗旱性。^{总的来说，我们通过介导 ABA 和 Ca 2+}信号转导通路中靶向转录本的m ⁶ A甲基化，揭示了影响棉花干旱反应的转录后修饰的新机制。