A comprehensive study of the physiology and chemistry of tea withering based on untargeted metabolomic, transcriptomic, and biochemical analyses

Withering is an important process for achieving high-quality flavor in tea. In this study, histological, metabolomics, transcriptomics, and biochemical analyses were combined to comprehensively explore the accumulation and molecular regulatory profiles of quality metabolites during tea withering. The results of tissue staining indicated that as the water content decreased, the vitality of the nucleus weakened, cytoplasmic content increased, flavone content decreased, and proteins degraded. Omics analysis showed that the total content of soluble sugars, free amino acids, and terpenoids increased, whereas that of catechins decreased significantly, although the caffeine content barely changed. Biochemical analysis revealed that the translated products of genes CSA010827 and CSA001819 catalyzed the biosynthesis of galactose and flavanol 3-O-glycosides, respectively, thereby increasing the content of soluble sugars and contributing to the astringent taste. Overall, by combining omics with histological and biochemical analyses, we revealed the metabolic profile and possible molecular mechanisms during the withering process of tea.