Two key genes boost galloylated catechin production in tea plants
image: Antisense oligonucleotide silencing analysis of CsSDH4 and CsSDH3 in tea plants. Values represent three biological replicate means ± SD. *P < 0.05, **P < 0.01 (Student’s t-test). (A) CsSDH4 antisense oligonucleotide analysis, (B) CsSDH4 expression level and catechins content in RNAi treatment of CsSDH4, (C) CsSDH4 antisense oligonucleotide analysis, (D) CsSDH3 expression level and catechins content in RNAi treatment of CsSDH3.
Credit: Horticulture Research
Catechins are the heart of tea’s flavor and health-promoting properties, especially the galloylated types such as EGCG and ECG. Yet the genetic basis of their biosynthesis has remained elusive. This study identified two shikimate dehydrogenases, CsSDH3 and CsSDH4, as essential enzymes catalyzing the formation of gallic acid, a precursor for galloylated catechins. Overexpression of these genes in transgenic tomato significantly elevated both gallic acid and catechin contents, while their silencing in tea leaves led to a marked reduction. These findings reveal a key metabolic route governing galloylated catechin synthesis, opening new possibilities for improving tea quality and nutritional value through molecular breeding.
Tea’s distinctive bitterness and astringency arise largely from galloylated catechins, compounds that also deliver antioxidant, anti-inflammatory, and anticancer benefits. The ratio of galloylated to nongalloylated catechins directly influences both taste and health-promoting properties, making it a crucial breeding target. Although prior studies identified enzymes involved in the later stages of catechin modification, the upstream formation of gallic acid—a key building block—remained poorly understood. This knowledge gap has limited precise manipulation of tea flavor and function. Based on these challenges, it is necessary to explore the genetic and biochemical mechanisms that drive gallic acid formation and galloylated catechin accumulation in tea plants.
Researchers from the Tea Research Institute of the Chinese Academy of Agricultural Sciences have identified two pivotal genes controlling the synthesis of galloylated catechins in Camellia sinensis. The study (DOI: 10.1093/hr/uhae356), published on April 1, 2025, in Horticulture Research, reveals that the shikimate dehydrogenases CsSDH3 and CsSDH4 catalyze the production of gallic acid, thereby enhancing catechin galloylation. By integrating QTL mapping, biochemical assays, and transgenic validation, the team uncovered a direct genetic link between shikimate metabolism and catechin biosynthesis—a finding that deepens our understanding of tea’s flavor chemistry and metabolic regulation.
Using a large LJ43 × BHZ F1 tea population, the team mapped a major quantitative trait locus (qGCI6.2) that explained up to 15.8% of the variation in galloylated catechin index (GCI). Within this locus, two genes—CsSDH3 and CsSDH4—were identified as candidates encoding shikimate dehydrogenases involved in gallic acid biosynthesis. Enzymatic assays confirmed that both proteins catalyze the conversion of 3-dehydroshikimate to gallic acid, with CsSDH4 showing higher catalytic efficiency. Expression analyses revealed strong correlations between CsSDH3/4 transcript levels, gallic acid content, and GCI in tea leaves. Functional studies in transgenic tomatoes further demonstrated that overexpressing these genes increased gallic acid and flavonoid levels, while transient silencing in tea leaves significantly reduced them. Transcriptomic analysis of overexpression lines showed upregulation of flavonoid biosynthetic genes, suggesting that CsSDH3 and CsSDH4 not only boost precursor availability but also enhance downstream flavonoid metabolism. Together, these results establish CsSDH3 and CsSDH4 as key regulators linking shikimate and flavonoid pathways to galloylated catechin biosynthesis in tea.
“Our study clarifies a long-standing question in tea biochemistry—how plants produce the gallic acid needed for catechin galloylation,” said Dr. Kang Wei, corresponding author of the study. “The discovery of CsSDH3 and CsSDH4 offers molecular targets for enhancing the formation of beneficial galloylated catechins like EGCG. This knowledge not only advances fundamental understanding of secondary metabolism in tea but also provides genetic tools for improving both taste and health attributes of future tea varieties.”
By pinpointing the genes responsible for galloylated catechin formation, this research paves the way for breeding tea cultivars rich in high-value bioactive compounds. Manipulating CsSDH3 and CsSDH4 expression could allow breeders to fine-tune catechin composition, achieving balanced flavor and enhanced antioxidant capacity. Beyond tea, these findings may also guide metabolic engineering in other plants to increase polyphenolic content for functional foods and nutraceuticals. Ultimately, understanding and controlling galloylation pathways could transform tea production—linking flavor excellence with verified health benefits and supporting the global demand for high-quality, health-promoting teas.
###
References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae356
Funding information
This work was supported by the Young Scientists Fund of the National Natural Science Foundation of China (32102441); and the China Agriculture Research System of MOF and MARA (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.