Functional analysis of a grape WRKY30 gene in drought resistance

WRKY transcription factors constitute a large protein family in plants and take part in a variety of stress response processes, such as drought resistance. In this study, the drought resistant function of a WRKY transcription factor gene WRKY30 from a wine grape cultivar ‘Vidal Blanc’ was investigated. Quantitative real-time PCR (qRT-PCR) analysis indicated that the expression of VvWRKY30 was induced by drought stress and stress response related signal molecules, such as abscisic acid (ABA), nitric oxide and salicylic acid. Phenotypic analysis of transgenic Arabidopsis indicated that over-expression of VvWRKY30 conferred increased drought resistance, demonstrated by enhancements in seed germination rate and root development, as well as a decrease in water loss and stomatal aperture under drought conditions. In further study, we found that VvWRKY30 resistance to drought occurred mainly by promoting the expression of regulators of an ABA-dependent and independent signal pathway. Over-expression of VvWRKY30 also up-regulated the expressions of proline synthetase gene P5CS1, sucrose synthase gene SS4, beta-amylase gene BAM4, glucose-6-phosphate dehydrogenase gene G6PDH, and antioxidant enzyme synthesis genes Cu/ZnSOD, CAT2 and POD2. The content of proline and soluble sugar, as well as the activities of superoxide dismutase, peroxidase, and catalase were increased. Overall, our results demonstrate that VvWRKY30 positively regulates drought response by regulating ABA signal pathway, modulating proline and soluble sugar metabolism, as well as activating the scavenging systems of reactive oxygen species.