γ-aminobutyric acid (GABA) is a signature bioactive compound in tea, contributing both to taste characteristics and to health-promoting properties. Traditional methods used to increase GABA content, such as anaerobic treatment during processing, often compromise flavor stability and disrupt flavonoid homeostasis. Meanwhile, flavonoids are key determinants of tea bitterness, astringency, and antioxidant capacity, and their biosynthesis is tightly connected to carbon and nitrogen metabolism. Although amino acid transporters are known to regulate nutrient allocation between plant tissues, their role in coordinating GABA accumulation with flavonoid metabolism in tea plants has not been fully understood. Based on these challenges, it is necessary to investigate the molecular mechanisms that connect amino acid transport with secondary metabolic pathways in tea.
Researchers from the Fruit and Tea Research Institute of the Hubei Academy of Agricultural Sciences and collaborating institutions report the discovery of a tea amino acid transporter that links GABA accumulation with flavonoid metabolism. The study, published (DOI: 10.1093/hr/uhaf261) in Horticulture Research in 2025, demonstrates that the transporter CsBAT directs amino acids from mature leaves to young shoots, where tea quality traits are established. Through genetic, physiological, and metabolic analyses, the team shows that CsBAT not only enhances GABA accumulation but also reshapes flavonoid-related pathways, revealing a coordinated mechanism underlying tea flavor formation.
Using a combination of yeast transport assays, transgenic Arabidopsis lines, and tea hairy-root systems, the researchers systematically characterized the function of CsBAT. The transporter showed high affinity for GABA as well as for theanine, glutamine, and glutamate, confirming its role as a central hub for amino acid movement. Spatial expression analyses revealed that CsBAT is predominantly localized in vascular tissues and is more strongly expressed in mature leaves than in young shoots, suggesting a role in long-distance source-to-sink transport.
Functional experiments demonstrated that enhanced CsBAT activity promotes the redistribution of amino acids toward young shoots, resulting in higher GABA accumulation in tissues used for tea production. In parallel, suppressing CsBAT altered the expression of key enzymes in flavonoid biosynthesis, including those involved in the phenylpropanoid pathway. Correlation analyses showed that changes in CsBAT expression could reverse the relationship between amino acid levels and flavonoid-related genes, indicating a tight metabolic crosstalk.
Together, these results reveal that CsBAT does more than transport amino acids: it coordinates carbon–nitrogen allocation and integrates primary and secondary metabolism. This coordinated regulation helps explain how tea plants balance flavor-enhancing amino acids with flavonoid composition during growth.
“Our findings identify CsBAT as a molecular link between amino acid transport and flavonoid metabolism,” the researchers note. “Rather than acting in isolation, GABA transport is embedded in a broader metabolic network that determines tea quality.” They emphasize that understanding how nutrients are redistributed within the plant provides a new perspective on quality formation, moving beyond single-pathway regulation. This work highlights the importance of transport processes in shaping metabolic outcomes and offers a framework for improving complex traits such as flavor and nutritional value through molecular breeding strategies.
The discovery of CsBAT has practical implications for tea breeding and quality improvement. By targeting a transporter that controls both GABA accumulation and flavonoid balance, breeders may be able to enhance desirable flavor and health attributes without relying on post-harvest treatments that compromise quality. More broadly, the study illustrates how manipulating nutrient transport can reprogram metabolic networks at the whole-plant level. This insight may extend beyond tea, providing strategies for improving quality traits in other crops where amino acids and secondary metabolites jointly determine taste, nutritional value, and stress resilience.
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References
DOI
10.1093/hr/uhaf261
Original Source URL
https://doi.org/10.1093/hr/uhaf261
Funding information
This work was supported by grants from the Hubei Provincial Key Research and Development Program (2024BBB080, 2024BBB081); the Hubei Provincial Natural Science Foundation (2019CFB178, 2022CFB472); Wuhan Industry University Research Special Project (2023110201030668); and the Earmarked Fund for China Agriculture Research System (CARS-19).
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.