Grapevines are economically important crops, yet their sensitivity to cold stress restricts cultivation to limited regions. To survive freezing temperatures, plants employ the ICE–CBF–COR regulatory pathway, where ICE transcription factors activate CBFs, which in turn trigger cold-responsive genes. Maintaining stability of ICE and CBFs is crucial for tolerance, but these proteins are subject to complex regulation, including ubiquitination. Although several U-box E3 ligases have been linked to drought and disease responses, little was known about their direct role in grape cold tolerance. Based on these challenges, it is necessary to investigate how ubiquitin ligases influence cold regulatory networks in grapevine.
A research team from Northwest A&F University, Henan Institute of Science and Technology, and collaborators reported their findings (DOI: 10.1093/hr/uhae297) on February 1, 2025, in Horticulture Research. The study identifies VviPUB19 as a critical factor undermining grapevine resilience to cold stress. By integrating molecular, genetic, and physiological analyses, the researchers uncovered how this E3 ligase promotes the degradation of transcription factors essential for activating protective cold-response genes.
The team first cloned the VviPUB19 gene from the cultivar ‘Thompson Seedless’ and confirmed that its expression is strongly induced by low-temperature treatment (4 °C). Functional assays in Arabidopsis revealed that plants overexpressing VviPUB19 were hypersensitive to freezing, showing higher electrolyte leakage and lower survival rates. Conversely, the atpub19 mutant displayed enhanced resistance, and this phenotype was reversed when complemented with VviPUB19. Transgenic grape lines overexpressing VviPUB19 showed wilting and increased oxidative stress markers under cold treatment, confirming reduced tolerance.
Mechanistic studies demonstrated that VviPUB19 physically interacts with VviICE1/2/3 and VviCBF1/2 through UND and ARM domains, leading to their proteasomal degradation. This suppression downregulated downstream cold-responsive genes, including VviCOR27 and VviLEA2. Interestingly, VviICEs also activated the VviPUB19 promoter, creating a regulatory loop that balances stress signaling with growth. This is the first report of an E3 ligase in grapevine directly destabilizing CBFs, revealing a novel layer of post-translational regulation within the ICE–CBF–COR pathway.
“Understanding the genetic mechanisms behind grapevine’s sensitivity to cold is crucial for expanding cultivation into harsher climates,” said Chaohong Zhang, senior author of the study. “Our discovery that VviPUB19 directly targets both ICE and CBF proteins for degradation provides an important missing piece in the puzzle of cold stress regulation. This work not only advances fundamental plant biology but also highlights potential genetic targets for breeding or biotechnological approaches to improve cold resilience in grapevine and possibly other fruit crops”.
The identification of VviPUB19 as a negative regulator of cold tolerance has significant implications for viticulture and crop improvement. By silencing or modifying this gene, breeders may enhance grape resilience in regions prone to frost and chilling damage. This could extend planting areas, stabilize yields, and reduce economic losses. Moreover, the findings open new directions for molecular breeding strategies that fine-tune the balance between growth and stress tolerance. Beyond grapevine, the mechanism uncovered here may apply to other crops, offering broader opportunities to engineer climate-resilient varieties amid global challenges of temperature fluctuations.
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References
DOI
10.1093/hr/uhae297
Original Source URL
https://doi.org/10.1093/hr/uhae297
Funding information
This work was supported by the Natural Science Foundation of China (No. 32072554), the National Key R&D Program of China (2019YFD1001405 and 2020YFD1000204).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.