Phosphorylation of VpCAMTA3 by VpCDPK13 enhances cold tolerance in grapevine.

Low temperature severely limits grapevine growth and productivity. In this study, VpCDPK13, a calcium-dependent protein kinase, was identified as a cold-inducible positive regulator in Vitis pseudoreticulata. Protein-protein interaction assays demonstrate that VpCDPK13 physically interacts with the transcription factor VpCAMTA3. Functional analyses reveal that both VpCAMTA3 and VpCDPK13 positively regulate grapevine cold tolerance. Moreover, in vitro kinase assays show that VpCDPK13 phosphorylates VpCAMTA3 at Thr588, Ser834, and Ser1049, and this phosphorylation further enhances the biological function of VpCAMTA3 under cold. Collectively, these findings establish the VpCDPK13-VpCAMTA3 signaling module as a key regulatory pathway that promotes grapevine adaption to cold stress.