Metabolomics and transcriptomics reveal the accumulation of key metabolites and flavor formation in the fresh leaves of wild and cultivated tea plants

The economic importance of tea plants for beverages is highlighted by metabolites of their fresh leaves, which significantly affect tea quality and flavor as processing precursors. This study compared metabolic traits in the fresh leaves of wild ancient tea (WT), cultivated ancient tea (CT), and cultivated terrace tea (TT) from Yunnan Province. It revealed the type differences in metabolites and their regulatory mechanism at the transcriptional level between the wild and cultivated fresh tea leaves. In this study, a total of 424 metabolites were identified with 327 differentially accumulated metabolites (DAMs). More flavonoid and amino acid DAMs related to tea taste and flavor accumulated abundantly in fresh CT leaves, indicating that the tea quality of CT may be more superior. Notably, the significantly increased quercetin glycosides and α-ionone in WT may serve as potential compounds and unique aroma, which helps differentiate the cultivated from wild type tea plants. TT demonstrated abundant accumulation of EGCG, D-valine, L-glutamic acid, and L-proline associated with bitterness, astringent, and umami flavors of tea, which lead to more intense and stronger flavor. Furthermore, flavonoids and amino acids associated with tea flavor were dominated by various metabolic and transcriptional responses in the different types of tea trees. Three correlation networks highly associated with variations in the contents of these components were identified using WGCNA, within which 15 MYB and bHLH TFs were predicted to regulate flavonoid and amino acid biosynthesis. This suggested a complex regulatory network underlying metabolic differences, but further investigations are required to understand their regulatory mechanism. These results may provide a theoretical basis for analyzing the variations in the tea quality of cultivated plants, and the conservation of wild plants, especially guiding the molecular breeding process in tea plants.