Journal of Tea Science Research, 2024, Vol.14, No.6, 313-321 http://hortherbpublisher.com/index.php/jtsr 313 Research Insight Open Access Secondary Metabolism in Tea Plants: Pathways and Regulatory Mechanisms Baofu Huang1, JieZhang2 1 Traditional Chinese Medicine Research Center, Cuixi Academy of Biotechnology, Zhuji, 311800, China 2 Institute of Life Sciences, Jiyang Colloge of Zhejiang A&F University, Zhuji, 311800, Zhejiang, China Corresponding author: jie.zhang@jicat.org Journal of Tea Science Research, 2024, Vol.14, No.6 doi: 10.5376/jtsr.2024.14.0029 Received: 28 Sep., 2024 Accepted: 30 Oct., 2024 Published: 20 Nov., 2024 Copyright © 2024 Huang and Zhang, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Huang B.F., and Zhang J., 2024, Secondary metabolism in tea plants: pathways and regulatory mechanisms, Journal of Tea Science Research, 14(6): 313-321 (doi: 10.5376/jtsr.2024.14.0029) Abstract Camellia sinensis, the tea plant, is an economically valuable crop globally due to its unique flavor, nutritional content, and cultural significance. Tea quality is largely a result of a versatile array of secondary metabolites, such as polyphenols, alkaloids, amino acids, and volatile aroma compounds, which are also largely involved in plant defense and environmental tolerance. New findings in plant molecular biology have allowed the identification in great detail of major biosynthetic pathways like the phenylpropanoid-flavonoid pathway, the MVA/MEP terpenoid biosynthetic pathways, purine and caffeine metabolism, and the theanine biosynthesis. Moreover, studies in mechanisms of regulation—spanning from transcription factors and non-coding RNAs to epigenetic modifications —have unraveled multilayered control mechanisms governing the biosynthesis of metabolites. The integration of transcriptomics, metabolomics, proteomics, and epigenomics has further revealed the spatial-temporal gene expression and metabolic dynamics upon environmental stimuli. The recent advances in tea plant secondary metabolism research are reviewed, application of gene editing, marker-assisted selection, and synthetic biology in metabolic engineering highlighted, and prospects and challenges in the future are elaborated. Increased understanding of secondary metabolic networks and their regulation will provide the major tools for molecular breeding and ensure the introduction of sustainable development in the tea industry. Keywords Tea plant; Secondary metabolism; Biosynthetic pathway; Regulatory mechanism; Molecular breeding 1 Introduction Tea, derived from the leaves of Camellia sinensis, is one of the most widely consumed non-alcoholic beverages globally. It holds tremendous economic importance, particularly in countries such as China, India, Kenya, and Sri Lanka, where tea production and export constitute a significant share of agricultural revenue. In addition to its economic value, tea is also recognized for its nutritional and health-promoting properties. Rich in antioxidants, amino acids, polyphenols, and caffeine, tea has been associated with numerous health benefits, including cardiovascular protection, anti-inflammatory effects, and cognitive enhancement (Wei et al., 2018). Secondary metabolites in tea plants—such as catechins, theanine, caffeine, and volatile aromatic compounds—play a central role in defining tea's flavor, aroma, and mouthfeel. These metabolites are also key indicators of quality and are often used in the classification and valuation of tea products (Li et al., 2016). Beyond their contributions to sensory properties, many of these compounds are integral to the plant’s defense system. They help protect against herbivores, pathogens, and environmental stressors, thereby supporting the plant’s survival and fitness in diverse ecological niches. It is essential for basic research and applied breeding work to understand how secondary metabolites are biosynthesized and regulated in tea plants. Their biosynthesis includes complex, multi-step enzymatic pathways with stringent controls at transcriptional, post-transcriptional, and epigenetic levels. Identification of important genes, enzymes, and regulatory networks provides a foundation for molecular breeding for improved quality, stress tolerance, and adaptation of tea (Wang et al., 2016; Liao et al., 2021). Further, advances in gene editing and multi-omics technologies open up possibilities for precision editing of metabolite profiles in tea cultivars.
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