RNA splicing pathway boosts grapevine salt tolerance
image: Biosynthesis of VvcircHMA1 and its role in salt stress regulation.
Credit: Horticulture Research
A research team has uncovered a hidden RNA-based mechanism that helps grapevines cope with salt stress, a growing challenge for fruit production in saline soils. The study shows that the grapevine gene VvU2A, which encodes a core component of the RNA splicing machinery, enhances salt tolerance by reshaping the production of circular RNAs (circRNAs). In particular, VvU2A suppresses the salt-sensitive circRNA VvcircHMA1, allowing VvmiR167b to reduce the activity of VvARF6, a negative regulator of salt tolerance. By linking RNA splicing, circRNA biogenesis, microRNA (miRNA) activity, and stress adaptation, the findings provide promising molecular targets for breeding grapevines better suited to saline environments.
Soil salinity severely restricts grapevine growth by damaging roots, limiting shoot development, disturbing sodium/potassium (Na+/K+) balance, and weakening photosynthesis. Previous studies of grapevine salt tolerance have mainly focused on transcriptional regulation, while post-transcriptional regulation remains less understood. CircRNAs, once regarded as unusual products of RNA processing, are increasingly recognized as active regulators of plant stress responses, yet how their formation is controlled under stress is still unclear. Due to these challenges, in-depth research is needed to clarify how spliceosomal factors and circRNA-mediated regulatory networks help grapevines adapt to salt stress.
The study was conducted by the Shandong Key Laboratory of Fruit and Vegetable Germplasm Innovation and Utilization and the College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, China. Published (DOI: 10.1093/hr/uhaf355) on December 22, 2025, in Horticulture Research, the research reveals a post-transcriptional regulatory pathway in which VvU2A enhances grapevine salt tolerance by modulating circRNA biogenesis and activating the VvcircHMA1–VvmiR167b–VvARF6 regulatory cascade.
The researchers first screened core members of the U2 small nuclear ribonucleoprotein (U2 snRNP) complex and found that VvU2A was strongly induced by salt treatment. When VvU2A was overexpressed in grape calli and grape plants with transgenic roots, the plants showed stronger growth under salt stress, higher antioxidant enzyme activity, better root activity, improved photosynthetic performance, reduced malondialdehyde (MDA) accumulation, and a lower Na+/K+ ratio. Knockdown of VvU2A produced the opposite pattern. CircRNA sequencing then identified 11,402 circRNAs, including 497 differentially expressed circRNAs regulated by VvU2A under salt stress. Among them, VvcircHMA1 emerged as a key salt-sensitive circRNA: its overexpression weakened grapevine growth under salinity. Further experiments showed that VvcircHMA1 functions as a competitive endogenous RNA (ceRNA), binding VvmiR167b and limiting its ability to cleave VvARF6. Functional assays confirmed that VvmiR167b enhances salt tolerance, while VvARF6 reduces it, forming a coherent regulatory pathway.
The authors said the study shows how a spliceosomal protein can influence plant stress resistance far beyond routine RNA processing. By lowering the level of one salt-sensitive circRNA, VvU2A protein helps free VvmiR167b to suppress VvARF6, shifting grapevine cells toward stronger protection under salinity. They said this work opens a new view of crop stress adaptation, where hidden RNA circuits help decide whether plants maintain growth, protect cellular function, and survive environmental pressure.
These findings offer a new molecular framework for improving grapevine performance in salt-affected soils. The VvU2A–VvcircHMA1–VvmiR167b–VvARF6 pathway provides potential markers or targets for molecular breeding, especially for cultivars expected to maintain root activity, photosynthesis, antioxidant capacity, and ion balance under saline irrigation or marginal land conditions. Beyond grapevine, the work also suggests that spliceosome-regulated circRNA networks may be more broadly involved in plant adaptation to environmental stress. Future studies could test whether similar pathways operate in other crops and identify downstream genes controlled by the VvARF6 transcription factor, helping translate this RNA-based mechanism into practical breeding strategies.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhaf355
Funding information
This research was supported by the Key R & D plan of Shandong Province (2022LZGCQY018), the National Natural Science Foundation of China (32572981 and 32572960), the China Agriculture Research System of MOF and MARA, and Shandong Provincial Colleges and Universities ‘Youth Innovation Technology Support Program' (2023KJ334).
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.