Drought is a major environmental factor limiting crop growth and development worldwide. WRKY transcription factor, a unique transcription factor in plants, has been shown to play important roles in plant response to abiotic stress. Previously, we have cloned the VvWRKY13 gene from resistant grape varieties and found that its expression was obviously induced by drought. Here we further explored the mechanism of VvWRKY13 in response to drought stress. After drought treatment, the expression of VvWRKY13 in the sensitive grape varieties was significantly higher than resistant grape varieties. Moreover, phenotypic changes of VvWRKY13 transgenic Arabidopsis were observed and drought-related indexes were detected under drought treatment. The results showed that VvWRKY13 transgenic Arabidopsis exhibited more sensitive phenotype to drought stress compared with wild type. The water loss rate of leaves in the transgenic Arabidopsis was significantly higher than wild type. The content of proline, soluble sugar and the expression of related genes decreased in transgenic Arabidopsis leaves under drought stress. The level of endogenous hydrogen peroxide and oxygen free radicals was increased, while the activity of catalase (CAT) and superoxide dismutase enzyme (SOD) were decreased. In addition, the expression of stress response gene was significantly decreased in transgenic Arabidopsis. Taken together, our results suggest that VvWRKY13 negatively modulates plant drought tolerance through regulating the metabolism of intracellular osmotic substances (proline, soluble sugar), the level of ROS, and the expression of stress-related genes.

中文翻译：

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转录因子VvWRKY13对葡萄的干旱胁迫的负调控

干旱是限制全球作物生长和发育的主要环境因素。WRKY转录因子是植物中独特的转录因子，已显示在植物对非生物胁迫的响应中起重要作用。以前，我们从抗性葡萄品种中克隆了VvWRKY13基因，发现其表达明显受干旱诱导。在这里，我们进一步探讨了VvWRKY13应对干旱胁迫的机制。干旱处理后，敏感葡萄品种中VvWRKY13的表达明显高于抗性葡萄品种。此外，观察到VvWRKY13转基因拟南芥的表型变化，并在干旱处理下检测到干旱相关指标。结果表明，与野生型相比，VvWRKY13转基因拟南芥对干旱胁迫表现出更敏感的表型。转基因拟南芥叶片的失水率明显高于野生型。干旱胁迫下转基因拟南芥叶片脯氨酸，可溶性糖含量及相关基因表达降低。内源性过氧化氢和氧自由基的水平增加，而过氧化氢酶（CAT）和超氧化物歧化酶（SOD）的活性降低。另外，转基因拟南芥中胁迫反应基因的表达明显降低。综上所述，我们的结果表明，VvWRKY13通过调节细胞内渗透物质（脯氨酸，可溶性糖）的代谢来负面调节植物的耐旱性，