VaWRKY26 transcription factor from Vitis amurensis negatively regulates plant cold tolerance

Overexpression of VaWRKY26 enhanced cold sensitivity by downregulating the expression of cold-responsive genes and suppressing ROS scavenging activity in Arabidopsis and grapevine. Grapevine (Vitis spp.) is an economically important fruit crop worldwide, yet its yield and cultivation distribution are substantially limited by cold stress. Amur grape (V. amurensis Rupr.) is a highly cold-tolerant species and is widely used as an elite breeding resource for developing climate-resilient grape cultivars. WRKY transcription factors play pivotal roles in modulating plant responses to diverse abiotic stresses. In this study, we isolated the VaWRKY26 from V. amurensis and characterized its biological function in cold stress. VaWRKY26 harbors two conserved WRKY domains, classifying it into the Group I subfamily. VaWRKY26 is expressed multiple organs, with the highest in leaves, and it peaked at 12 h post treatment under cold stress. Physiological assays demonstrated that VaWRKY26 overexpression promoted reactive oxygen species (ROS) accumulation, suppressed activities of antioxidant enzymes, decreased proline content, and increased the malondialdehyde content and electrolyte leakage. Moreover, VaWRKY26 significantly repressed the expression of cold-responsive genes, including C-repeat binding factors (CBFs) and cold-regulated (COR) genes. In contrast, transient silencing of VaWRKY26 yielded the opposite results. Collectively, our findings demonstrate that VaWRKY26 acts as a negative regulator of cold tolerance in both Arabidopsis and grapevine. It impairs plant cold tolerance by inhibiting ROS scavenging capacity and repressing the CBF-COR signaling pathway. This study provides novel insights into the molecular mechanism of VaWRKY26 in modulating grapevine cold tolerance and offers a valuable gene resource for the molecular breeding of cold-tolerant grape cultivars.