• Reactive oxygen species (ROS) act as important secondary messengers in abscisic acid (ABA) signaling and induce stomatal closure under dehydration stress. The breast cancer susceptibility gene 1 (BRCA1), an important tumor suppressor in animals, functions primarily in the maintenance of genome integrity in animals and plants. However, whether and how the plant BRCA1 regulates intracellular ROS homeostasis in guard cells under dehydration stress remains unknown.
• Here, we found that Arabidopsis atbrca1 loss‐of‐function mutants showed dehydration stress tolerance. This stress tolerant phenotype of atbrca1 was a result of ABA‐ and ROS‐induced stomatal closure, which was enhanced in atbrca1 mutants compared with the wild‐type. AtBRCA1 downregulated the expression of ROS‐responsive and marker genes. Notably, these genes were also the targets of the AP2/ERF transcriptional activator RRTF1/ERF109.
• Under normal conditions, AtBRCA1 physically interacted with RRTF1 and inhibited its binding to the GCC‐box‐like sequence in target gene promoters. Under dehydration stress, the expression of AtBRCA1 was dramatically reduced and that of RRTF1 was activated, thus inducing the expression of ROS‐responsive genes.
• Overall, our study reveals a novel molecular function of AtBRCA1 in the transcriptional regulation of intracellular ROS homeostasis under dehydration stress.

中文翻译：

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脱水胁迫下拟南芥BRCA1抑制RRTF1介导的ROS产生和ROS反应基因表达。

• 活性氧（ROS）在脱落酸（ABA）信号传导中充当重要的次要信使，并在脱水胁迫下诱导气孔关闭。乳腺癌易感基因1（BRCA1）是动物中重要的肿瘤抑制因子，主要在维持动植物基因组完整性方面起作用。然而，在干旱胁迫下，植物BRCA1是否以及如何调节保卫细胞内的细胞内ROS稳态仍未知。
• 在这里，我们发现拟南芥 atbrca1功能丧失的突变体表现出脱水胁迫耐受性。atbrca1的这种耐胁迫表型是ABA和ROS诱导的气孔关闭的结果，与野生型相比，atbrca1突变体中这种增强。AtBRCA1下调ROS反应性和标记基因的表达。值得注意的是，这些基因也是AP2 / ERF转录激活因子RRTF1 / ERF109的靶标。
• 在正常情况下，AtBRCA1与RRTF1发生物理相互作用，并抑制其与靶基因启动子中的GCC-box-like序列结合。在脱水胁迫下，AtBRCA1的表达显着降低，而RRTF1的表达被激活，从而诱导了ROS反应基因的表达。
• 总的来说，我们的研究揭示了AtBRCA1在脱水应激下细胞内ROS稳态的转录调控中的新型分子功能。