Under stress conditions, plants modulate their internal states and initiate various defence mechanisms to survive. The ubiquitin-proteasome system is one of the critical modules in these mechanisms, and Plant U-Box proteins play an important role in this process as E3 ubiquitin ligases. Here, we isolated the Plant U-box 24 gene CaPUB24 (Capsicum annuum Plant U-Box 24) from pepper and characterized its functions in response to drought stress. We found that, compared to the other CaPUBs in the same group, the expression of CaPUB24 was significantly induced by drought stress. We also found that CaPUB24 was localized to the nucleus and cytoplasm and had E3 ubiquitin ligase activity. To investigate the biological role of CaPUB24 in response to drought stress further, we generated CaPUB24-silenced pepper plants and CaPUB24-overexpressing Arabidopsis transgenic plants. CaPUB24-silenced pepper plants exhibited enhanced drought tolerance compared to the control plants due to reduced transpirational water loss and increased abscisic acid (ABA) sensitivity. In contrast, CaPUB24-overexpressing Arabidopsis transgenic plants exhibited reduced drought tolerance and ABA-insensitive phenotypes. Our findings suggest that CaPUB24 negatively modulates drought stress response in an ABA-dependent manner.

中文翻译：

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Pepper U-Box E3 泛素连接酶 24，CaPUB24，负向调节干旱胁迫反应

在胁迫条件下，植物调节其内部状态并启动各种防御机制以求生存。泛素-蛋白酶体系统是这些机制中的关键模块之一，植物 U-Box 蛋白作为 E3 泛素连接酶在此过程中发挥着重要作用。在这里，我们从辣椒中分离出了植物 U-box 24 基因CaPUB24（C apsicum a nnuum Plant U - B ox 24），并表征了其响应干旱胁迫的功能。我们发现，与同组中的其他CaPUB相比， CaPUB24的表达受到干旱胁迫的显着诱导。我们还发现CaPUB24定位于细胞核和细胞质并具有E3泛素连接酶活性。为了进一步研究CaPUB24在响应干旱胁迫中的生物学作用，我们产生了CaPUB24沉默的辣椒植物和CaPUB24过表达的拟南芥转基因植物。与对照植物相比， CaPUB24沉默的辣椒植物由于蒸腾失水减少和脱落酸（ABA）敏感性增加而表现出增强的耐旱性。相反，CaPUB24过表达的拟南芥转基因植物表现出耐旱性降低和ABA不敏感表型。我们的研究结果表明，CaPUB24 以 ABA 依赖性方式负向调节干旱胁迫反应。