Drought is a kind of adversity that has always severely restricted the growth of grapes. Flavonols, as flavonoid compounds, are abundant in grapes and have an indispensable function in resisting drought. Hereafter, the objectives of this investigation were to identify key drought-induced transcription factors in grape and explore their roles and regulatory networks in the flavonol-mediated drought response mechanism. In this study, one-year-old cutting seedlings of ‘Cabernet Sauvignon’ grape were used as experimental materials, cultivated in a solar greenhouse, and subjected to moderate drought treatment. The physiological and biochemical parameters related to stress and flavonol content in plant tissues were determined, and gene expression, functional validation, and transcriptional regulation relationships were explored. The results showed that the growth of grape plants was affected under drought conditions, the flavonol accumulation and the expression level of VviMYB24 were significantly induced by drought stress. Overexpression of VviMYB24 reduced the degree of cytoplasmic membrane damage and induced flavonol biosynthesis to confer drought tolerance in Arabidopsis plants and grape callus. Further study revealed that VviMYB24 can interact with the bHLH transcription factor VviMYC2b, which was positively responsive to drought, and they could activate VviFLS5 expression individually and/or in combination in the form of a complex. Interestingly, VviMYB24 could positively regulate VviMYC2b expression to form a transcriptional cascade, enhancing the function of the complex. Transient overexpression of VviMYB24, VviMYC2b, and VviFLS5 in grape leaves promoted the drought-responsive flavonol accumulation. Overall, the above data elucidated that the VviMYB24-VviMYC2b-VviFLS5 module positively regulates drought-induced flavonol biosynthesis in response to drought stress in grape, which contributes to further grape drought resistant breeding and variety improvement through biotechnology.

中文翻译：

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VviMYB24 正向调节 'Cabernet Sauvignon' 葡萄幼苗中度干旱胁迫下黄酮醇的生物合成


干旱是一种一直严重限制葡萄生长的逆境。黄酮醇作为类黄酮化合物，在葡萄中含量丰富，具有不可或缺的抗旱功能。此后，本研究的目的是确定葡萄中关键的干旱诱导转录因子，并探索它们在黄酮醇介导的干旱响应机制中的作用和调控网络。在本研究中，以 'Cabernet Sauvignon' 葡萄的一年生扦插苗为实验材料，在日光温室中培育，并进行中度干旱处理。测定植物组织中与胁迫和黄酮醇含量相关的生理生化参数，并探讨基因表达、功能验证和转录调控关系。结果表明，干旱条件下葡萄植株的生长受到影响，干旱胁迫显著诱导了葡萄植株黄酮醇积累和 VviMYB24 表达水平。VviMYB24 的过表达降低了细胞质膜损伤的程度，并诱导黄酮醇生物合成赋予拟南芥植物和葡萄愈伤组织耐旱性。进一步研究显示，VviMYB24 可以与 bHLH 转录因子 VviMYC2b 相互作用，后者对干旱有正响应性，它们可以以复合物的形式单独和/或组合激活 VviFLS5 表达。有趣的是，VviMYB24 可以正向调节 VviMYC2b 表达以形成转录级联反应，从而增强复合物的功能。葡萄叶片中 VviMYB24 、 VviMYC2b 和 VviFLS5 的瞬时过表达促进了干旱响应性黄酮醇的积累。 综上所述，上述数据阐明了 VviMYB24-VviMYC2b-VviFLS5 模块响应葡萄干旱胁迫正向调节干旱诱导的黄酮醇生物合成，有助于通过生物技术进一步提高葡萄抗旱育种和品种改良。