Negative regulation by transcription factor VvWRKY13 in drought stress of Vitis vinifera L

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.