Vine in peril: discovery of cold-sensitivity gene in grapes offers new clues
image: A model of VviPUB19 negatively regulates grape cold tolerance. Low temperature induces ICEs gene expression, which activates the activity of PUB19 promoter to increase its gene expression.
Credit: Horticulture Research
Grapevines, widely valued for their fruit and wine, are especially vulnerable to cold temperatures. A new study has uncovered a key genetic factor that actually weakens the plant's natural defense against freezing stress. The gene, VviPUB19, was found to reduce cold tolerance by promoting the degradation of proteins that usually protect the plant under low temperatures. Tests in both grape and Arabidopsis confirmed that plants with higher levels of VviPUB19 were more cold-sensitive, while those without it were more resilient. These findings highlight a previously unknown negative regulator of cold stress pathways in plants.
Cold damage is a major limiting factor for grapevine production, affecting plant health, fruit yield, and geographic cultivation range. To combat cold, plants activate protective pathways regulated by ICE and CBF transcription factors, which switch on cold-responsive genes. These regulatory proteins must be tightly controlled, especially under changing weather conditions. One critical mechanism is protein degradation, orchestrated by ubiquitin ligases—enzymes that tag specific proteins for removal. However, the specific roles of these enzymes in downregulating cold tolerance in grapevines remained poorly understood. Due to these challenges, deeper insight into these “brake” mechanisms is needed to fully understand—and possibly override—cold susceptibility in grapes.
A research team from Northwest A&F University has identified a surprising molecular “off-switch” for cold defense in grapevines. Their study (DOI: 10.1093/hr/uhae297), published on October 23, 2024, in Horticulture Research, reveals that the ubiquitin ligase VviPUB19 interacts with and destabilizes key cold-response regulators, reducing the plant's ability to withstand freezing. By combining genetic transformation, protein interaction analysis, and cold treatment experiments, the researchers uncovered a dual role for VviPUB19 in orchestrating the degradation of ICE and CBF proteins—key players in the cold-stress response.
The team discovered that VviPUB19 is upregulated in grape leaves exposed to 4°C. However, instead of enhancing resistance, the gene reduced it. When overexpressed in both grapevine and Arabidopsis, plants showed increased cell damage, oxidative stress, and lower survival under freezing temperatures. Conversely, Arabidopsis mutants lacking PUB19 were significantly more cold-tolerant.
Further molecular studies revealed that VviPUB19 physically binds to ICE1/2/3 and CBF1/2 transcription factors, targeting them for degradation via the proteasome pathway. This interaction was confirmed through yeast two-hybrid and fluorescence assays. Interestingly, the ICE proteins also activated VviPUB19 gene expression—creating a feedback loop that finely tunes the cold response. Additionally, the overexpression of VviPUB19 led to suppressed expression of key cold-responsive genes like COR27A and KIN2, along with reduced antioxidant enzyme activity.
This study is the first to identify an E3 ubiquitin ligase in grapevine that directly targets and destabilizes CBF proteins, revealing a crucial new layer of post-translational regulation in plant cold tolerance.
“This work reveals an unexpected regulatory circuit where the very proteins that defend the plant against cold also trigger their own regulator—VviPUB19—which then undermines that defense,” said Dr. Chaohong Zhang, senior author of the study. “It's a sophisticated feedback system that likely exists to balance growth and survival. Understanding it gives us a new handle on how plants make survival decisions in harsh environments.”
This discovery offers a promising target for genetic improvement of grapevines. By silencing or modifying VviPUB19, breeders may enhance cold tolerance in cultivars grown in temperate and high-latitude regions. The findings also provide a blueprint for uncovering similar negative regulators in other crops, opening new avenues for improving stress resistance through precise control of protein degradation. In the face of increasing climate variability, this knowledge could support the development of more resilient agricultural systems that can better adapt to extreme weather.
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References
DOI
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.