The ubiquitin ligase VviPUB19 negatively regulates grape cold tolerance by affecting the stability of ICEs and CBFs

Cold stress seriously affects the plant growth and development. The ubiquitination system plays an important role by degrading and modifying substrates at the protein level. In this study, the U-box type ubiquitin ligase VviPUB19 gene was induced by low temperature (4°C) in grapevine. In Arabidopsis thaliana, the pub19 mutant, a homologous mutation of VviPUB19, exhibited enhanced cold tolerance, and the resistance phenotype of the mutant could be attenuated by VviPUB19. VviPUB19 overexpressing grape lines exhibited lower cold tolerance. Furthermore, it was revealed that VviPUB19 interacted with the cold-related transcription factors VviICE1, 2 and 3 and VviCBF1 and 2, and was involved in the degradation of them. This is the first time that an E3 ligase (VviPUB19) that interacts with CBFs and affects its protein stability has been identified. It was also shown that VviICE1, 2 and 3 positively regulated VviPUB19 promoter activity. Therefore, our results suggest that VviPUB19 reduces grape cold tolerance via participating in the CBF-dependent pathway.