• Plant stomata play a crucial role in leaf function, controlling water transpiration in response to environmental stresses and modulating the gas exchange necessary for photosynthesis. The phytohormone abscisic acid (ABA) promotes stomatal closure and inhibits light‐induced stomatal opening. The Arabidopsis thaliana E3 ubiquitin ligase COP1 functions in ABA‐mediated stomatal closure. However, the underlying molecular mechanisms are still not fully understood.
• Yeast two‐hybrid assays were used to identify ABA signaling components that interact with COP1, and biochemical, molecular and genetic studies were carried out to elucidate the regulatory role of COP1 in ABA signaling.
• The cop1 mutants are hyposensitive to ABA‐triggered stomatal closure under light and dark conditions. COP1 interacts with and ubiquitinates the Arabidopsis clade A type 2C phosphatases (PP2Cs) ABI/HAB group and AHG3, thus triggering their degradation. Abscisic acid enhances the COP1‐mediated degradation of these PP2Cs. Mutations in ABI1 and AHG3 partly rescue the cop1 stomatal phenotype and the phosphorylation level of OST1, a crucial SnRK2‐type kinase in ABA signaling.
• Our data indicate that COP1 is part of a novel signaling pathway promoting ABA‐mediated stomatal closure by regulating the stability of a subset of the Clade A PP2Cs. These findings provide novel insights into the interplay between ABA and the light signaling component in the modulation of stomatal movement.

中文翻译：

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COP1 通过调节 ABI/HAB 和 AHG3 磷酸酶的丰度促进 ABA 诱导的气孔关闭

• 植物气孔在叶片功能、控制水分蒸腾以响应环境压力和调节光合作用所需的气体交换方面发挥着至关重要的作用。植物激素脱落酸 (ABA) 促进气孔关闭并抑制光诱导的气孔开放。拟南芥E3泛素连接酶 COP1 在 ABA 介导的气孔关闭中起作用。然而，潜在的分子机制仍未完全了解。
• 酵母双杂交法用于鉴定与 COP1 相互作用的 ABA 信号成分，并进行了生化、分子和遗传研究以阐明 COP1 在 ABA 信号中的调节作用。
• cop1突变体在光照和黑暗条件下对 ABA 触发的气孔关闭不敏感。COP1 与拟南芥进化枝 A 型 2C 磷酸酶 (PP2Cs) ABI/HAB 组和 AHG3 相互作用并泛素化，从而引发它们的降解。脱落酸增强了 COP1 介导的这些 PP2C 的降解。ABI1 和 AHG3 的突变部分挽救了cop1气孔表型和 OST1 的磷酸化水平，OST1 是 ABA 信号传导中的关键 SnRK2 型激酶。
• 我们的数据表明，COP1 是通过调节 Clade A PP2C 子集的稳定性来促进 ABA 介导的气孔关闭的新型信号通路的一部分。这些发现为 ABA 和光信号成分在气孔运动调节中的相互作用提供了新的见解。