Water channels switch on dormancy in litchi buds

Bud dormancy is essential for the seasonal growth rhythm of perennial plants, yet its regulation in tropical evergreen species remains poorly understood. New research reveals that the onset of dormancy in litchi terminal buds is tightly linked to changes in internal water status controlled by specific aquaporin proteins. The study shows that two plasma membrane aquaporins act cooperatively to regulate water loss from buds, thereby promoting dormancy initiation. By integrating physiological measurements with molecular and genetic analyses, the research uncovers a regulatory pathway in which water transport dynamics, hormone signaling, and transcriptional control converge to determine when buds cease growth. These findings provide new insight into dormancy regulation beyond temperate species.

In woody perennials, bud dormancy allows plants to survive unfavorable conditions and synchronize growth with seasonal cues. While dormancy mechanisms have been extensively studied in temperate deciduous trees, much less is known about how dormancy is initiated in tropical evergreen fruit trees such as litchi. Previous studies suggest that hormones like ethylene and abscisic acid influence dormancy, but the downstream physiological processes remain unclear. Water content within buds changes dramatically as growth slows and dormancy begins, hinting at a role for water transport regulation. Based on these challenges, it is necessary to conduct in-depth research on how water movement is controlled during dormancy onset in evergreen species.

Researchers from South China Agricultural University report new insights into dormancy regulation in litchi buds in a study published (DOI: 10.1093/hr/uhaf122) on May 7, 2025, in Horticulture Research. The team demonstrates that two aquaporin proteins, LcPIP1;4 and LcPIP1;4a, regulate the onset of terminal bud dormancy by controlling water transport. Using imaging, gene silencing, and hormone treatments, the study links molecular regulation of aquaporins with changes in bud moisture content and growth cessation.

The researchers first tracked water status across four developmental stages of litchi terminal buds using low-field nuclear magnetic resonance and magnetic resonance imaging. Dormant buds contained mainly bound water and showed minimal water mobility, while actively growing buds accumulated free water. As growth ceased, free water declined sharply, indicating restricted water transport into the bud. Transcriptome analysis identified two aquaporin genes whose expression correlated with these changes. Functional experiments revealed that silencing either aquaporin delayed dormancy onset and increased bud water content, while simultaneous silencing produced an even stronger effect.

Further molecular analyses showed that the two aquaporins physically interact at the plasma membrane, forming functional complexes that enhance water loss during dormancy initiation. The study also identified a transcription factor that directly activates one aquaporin gene and demonstrated that hormone signals modulate this pathway. Ethylene suppressed aquaporin expression, while abscisic acid promoted it, revealing a finely tuned regulatory balance. Together, these results establish a mechanistic link between water transport proteins, hormonal control, and dormancy timing in a tropical evergreen fruit tree.

“This work highlights water transport as a central driver of dormancy onset rather than a passive consequence,” the authors note. By showing that aquaporins actively promote water loss in terminal buds, the study reframes dormancy as a process controlled at the cellular membrane level. The researchers emphasize that this mechanism differs from classical temperature- and photoperiod-driven models developed in temperate trees, suggesting that evergreen species rely on distinct regulatory strategies adapted to subtropical environments.

Understanding how dormancy is regulated in litchi has practical implications for fruit production in subtropical and tropical regions. Manipulating aquaporin activity or hormone signaling could offer new strategies to manage vegetative growth cycles, synchronize flowering, and improve yield stability under changing climate conditions. More broadly, the findings provide a conceptual framework for studying dormancy in other evergreen crops, including citrus and mango. By linking water transport regulation to developmental timing, the research opens new avenues for breeding and biotechnological approaches aimed at optimizing perennial crop performance.

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References

DOI

10.1093/hr/uhaf122

Original Source URL

https://doi.org/10.1093/hr/uhaf122

Funding information

This study was supported by the China Litchi and Longan Industry Technology Research System (project no. CARS-32), and 2023 Special Project for Key Areas of Research and Development of Guangzhou Municipality (2023B01J2002), Guangzhou Basic and Applied Basic Research Foundation (No. 2024A04J4919), Open project of Key Laboratory of Genetic Resources Evaluation and Utilization of Tropical Fruits and Vegetables (Co-construction by Ministry and Province), Ministry of Agriculture and Rural Affairs (ITFT2024PT0203), and Construction Plan of Guangdong Province High-level Universities and the Research Start-up Funds for the High-level Talent Introduction Project of South China Agricultural University (5300-223109).

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.