Free amino acids (FAAs) critically influence the palatability of tea, particularly theanine, which imparts the characteristic umami flavor to tea infusions. Nonetheless, their concentrations exhibit considerable variability across distinct tea cultivars, thereby shaping both the gustatory profile and nutritional composition of the beverage. In a recent investigation spearheaded by the Tea Research Institute affiliated with the Chinese Academy of Agricultural Sciences and Huazhong Agricultural University, a collection of 339 tea accessions was examined to elucidate FAA levels and unravel their mechanisms of variation and accumulation. The outcomes provide valuable perspectives and advantages for the preservation, assessment, and exploitation of tea genetic resources, ultimately aiming for the genetic enhancement and development of tea plants, and furnish essential data and methodologies for further decoding intricate composite traits within tea species.
By analyzing the variation of FAAs among 339 tea accessions in two years, we can know that the determined components of FAAs including arginine, glutamine, glutamate, alanine, and theanine with the highest diversity index differed among different genetic resources and intraspecific accessions. Meanwhile, their amounts in Camellia sinensis were all significantly higher than in the wild relatives. The study confirmed the significant opposite trend between chlorophyll and FAA profiles. Image credit: Sci.News.
“Camellia sinensis, the tea plant, along with its wild congeners, are evergreen, woody perennial trees belonging to the genus Camellia within the family Theaceae, boasting a venerable cultivation history,” remarked co-senior author Dr. Liang Chen from the Tea Research Institute and his associates.
“These beverages have ascended to become the most significant non-alcoholic drinks globally, owing to their widespread consumption and their origins in southwestern China.”
“For commercial viability and quality assessment, the secondary metabolites present in tea plants serve as paramount indicators associated with desirable flavors, nutritional richness, and a plethora of health advantages, encompassing polyphenols, catechins, caffeine, theanine, and terpenes.”
“Consequently, the rigorous evaluation and strategic utilization of tea accessions are fundamentally crucial for facilitating the discovery and development of novel cultivars.”
“Among these, distinct tea cultivars characterized by traits such as albinism, purple coloration, and other variations possess unique attributes that contribute to the formation and concentration of valuable secondary metabolites, underpinning their functional properties.”
“An elevated concentration of theanine in albino tea cultivars, which are distinguished by their abundant white and yellowish tender leaves, not only enhances the umami savor of the tea infusion but also offers protective benefits against various detrimental health conditions, including obesity, inflammation, and the aging process.”
Within the scope of this research, the investigators undertook an in-depth examination of 339 tea accessions to elucidate the genetic and metabolic factors governing the variability and accumulation of FAAs, with a pronounced emphasis on theanine.
Their findings revealed that cultivated tea varieties exhibited superior levels of theanine when contrasted with their wild counterparts, suggesting a genetic enrichment driven by the process of domestication.
Alanine and theanine demonstrated the highest diversity indices, underscoring their pivotal role in defining the quality characteristics of tea.
Furthermore, the scientific team identified phytochrome interacting factor 1 (CsPIF1) as a principal negative regulator influencing theanine content.
Upon transient suppression of CsPIF1 expression in tea plants, a notable augmentation in theanine levels was observed, a phenomenon corroborated in the model organism Arabidopsis.
This groundbreaking discovery establishes a foundation for future investigations employing gene editing technologies with the objective of modulating theanine biosynthesis, transport, and hydrolysis pathways, thereby presenting novel opportunities for tea quality enhancement through directed genetic modifications.
“Our research not only deepens the comprehension of the genetic architecture of tea but also inaugurates uncharted territories for precision breeding initiatives,” stated Dr. Chen.
“By judiciously manipulating the expression of CsPIF1 and associated genes, we possess the potential to elevate theanine concentrations, thereby directly impacting the nutritional value and sensory attributes of tea.”
“Such insights hold the promise of revolutionizing the tea industry, equipping breeders with advanced tools to meticulously refine flavor profiles and augment the health-promoting properties of tea through sophisticated genetic interventions.”
The results of this study have been published in the esteemed journal Horticulture Research.
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Rong Huang et al. 2024. Comprehensive dissection of variation and accumulation of free amino acids in tea accessions. Horticulture Research 11 (1): uhad263; doi: 10.1093/hr/uhad263
