Combined metabolic phenotypes and gene expression profiles revealed the formation of terpene and ester volatiles during white tea withering process

Withering is a critical process to form the unique aroma of high-quality white tea. To study the mechanism underlying aroma changes during the white withering, we herein conducted volatile metabolomics and transcriptomics of the young leaves from the 'Fuding Dahaocha' tea cultivar. As the withering time extended, the content of major aroma components increased significantly, score of sensory evaluation and Owuor's flavor index (OFI) also increased. The aromatic substances that accumulated during white tea withering were mainly volatile terpenes, and esters. Their change trends were largely consistent with the gene expression of the α-linolenic acid metabolic pathways, while the correlation between the trends in volatiles and the gene expression of the terpenoid biosynthesis pathways was more complex and induced by the jasmonic acid (JA) signaling pathway. Additionally, we also explored the regulation pattern of key genes in the signaling pathway by related transcription factors. Three coexpression networks strongly correlated to the variation of volatile component content during propagation were identified by weighted gene coexpression network analysis (WGCNA). Our results provide a new perspective on the processing mechanism and quality improvement of white tea.