VvWRKY70, a newly identified grape WRKY transcription factor, confers drought tolerance via coordinated physiological...

Drought is a key factor limiting grape yield, making it crucial to reveal the underlying response mechanisms of plants to environmental stress. Although WRKY transcription factors play multiple roles in plant development and stress responses, only a few have been functionally characterized in Vitis vinifera L.. In this study, VvWRKY70, from V. vinifera, was cloned and identified in transgenic A. thaliana plants and grape seedlings. VvWRKY70 protein was localized to the nucleus and exhibited the W-box binding activity. VvWRKY70 expression was rapidly induced by drought stress, and heterologous VvWRKY70 overexpression in A. thaliana plants enhanced drought tolerance, as evidenced by improved seed germination, seedling development, and survival capability. VvWRKY70 overexpression contributed to the reduction of stomatal aperture and the accumulation of osmotic adjustment substances including proline and soluble sugar. Moreover, VvWRKY70 overexpression increased the activities of superoxide dismutase, catalase, and peroxidase, promoted anthocyanin accumulation, and effectively reduced the content of hydrogen peroxide and malondialdehyde under water stress. Notably, transient overexpression of VvWRKY70 in grapevine led to the upregulation of both drought-responsive marker genes (VvRD22, VvRD29A, VvDREB2A and VvERD14) and defense-related genes (VvCHS, VvF3'H, VvDFR, VvPOD4 and VvP5CS). These findings indicate that VvWRKY70 can directly modulate the transcription of these genes and thereby participate in the corresponding physiological processes. These results demonstrate that VvWRKY70 could be a promising candidate gene in grape for adapting to water scarcity.