Tea plants are known hyperaccumulators of fluoride, storing 10–100 times more fluoride than many other crop species. While fluoride tolerance enables tea plants to thrive in various environments, long-term consumption of high-fluoride tea products poses potential risks, including dental and skeletal fluorosis. Fluoride is absorbed by roots and transported upward, but the membrane transporters responsible for root-level fluoride movement have remained unclear. Previous research suggested that members of the NPF (Nitrate Transporter 1/Peptide Transporter Family) can transport halogen ions such as chloride, raising the possibility that similar transporters may also mediate fluoride movement. Due to these challenges, deeper investigations into fluoride uptake and transport mechanisms are needed.
A research team from Anhui Agricultural University reported (DOI: 10.1093/hr/uhaf072) on March 3, 2025, in Horticulture Research that they have identified CsNPF2.3, a root-specific transporter gene that governs fluoride uptake and movement in Camellia sinensis. Through transcriptome sequencing, heterologous expression in yeast, tissue localization, and hairy root overexpression, the team confirmed that CsNPF2.3 transports fluoride across membranes and significantly increases fluoride accumulation in multiple tissues. This discovery offers new insight into how fluoride travels within tea plants.
The study was initiated after researchers observed that selenium addition reduced fluoride concentration in tea leaves by lowering its translocation efficiency from root to shoot. Transcriptome profiling of selenium–fluoride co-treated roots identified several NPF genes, among which CsNPF2.3 stood out due to its strong expression in roots and correlation with fluoride transport traits. Phylogenetic analysis revealed that CsNPF2.3 is closely related to known chloride transporters, suggesting possible fluoride transport capacity. Expression analyses showed that CsNPF2.3 is predominantly expressed in epidermal, cortex, and xylem parenchyma cells—critical tissues for radial ion transport. In yeast, expression of CsNPF2.3 caused significantly higher intracellular fluoride accumulation and increased growth inhibition under high-fluoride conditions, demonstrating its transport activity. Subcellular localization further confirmed that CsNPF2.3 is positioned at the plasma membrane.
To examine its physiological role, the researchers generated tea hairy roots overexpressing CsNPF2.3. These transgenic plants accumulated noticeably more fluoride in roots, stems, and leaves and exhibited a substantially higher leaf-to-root fluoride ratio. Across nine tea cultivars, CsNPF2.3 expression levels were strongly positively correlated with fluoride content in both roots and leaves, as well as with root-to-leaf transport efficiency. Together, the findings establish CsNPF2.3 as a central regulator of fluoride distribution in tea plants.
“Our work identifies CsNPF2.3 as the first root-localized transporter directly linked to fluoride uptake and movement in tea plants,” the research team explained. “By demonstrating where the transporter is expressed, how it functions at the membrane level, and how it influences fluoride content in different tissues, we have filled a long-standing gap in understanding fluoride hyperaccumulation in tea. This discovery also explains why cultivars differ in their fluoride levels and highlights CsNPF2.3 as a promising target for agricultural and breeding innovations.”
The discovery of CsNPF2.3 provides new opportunities for creating low-fluoride tea varieties and managing fluoride levels through agronomic practices. Breeders can use CsNPF2.3 expression as a molecular marker for selecting or developing cultivars that limit fluoride translocation to leaves. The transporter's behavior under environmental treatments, such as selenium application, also offers potential pathways for reducing fluoride accumulation in the field. Ultimately, understanding this root-based transport mechanism paves the way for producing safer tea products while supporting sustainable tea cultivation.
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References
DOI
10.1093/hr/uhaf072
Original Source URL
https://doi.org/10.1093/hr/uhaf072
Funding information
This work was supported by the National Key Research and Development Program of China (No. 2021YFD1601100), the Research Funds of Joint Research Center for Food Nutrition and Health of IHM (No. 2023SJY01), Excellent scientific research and innovation team of universities in Anhui Province (No. 2022AH010055), the earmarked fund for CARS (No. CARS-19), and Natural Science Foundation of China (No. 32172636).
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.