Transcriptome Study on Biosynthesis of Volatile Organic Compounds During Manufacturing Process of Semi-fermented Tea
Date Issued
2015
Date
2015
Author(s)
Wu, Ying-Jou
Abstract
Tea plant (Camellia sinensis (L.) O. Kuntze) is a beverage crop, with great economic value and is consumed worldwide, in which semi-fermented oolong tea is an important feature of teas in Taiwan. The particular manufacturing process of semi-fermented tea involves plucking, solar withering, indoor withering, panning, rolling and drying, gives the tea a unique floral and fruity aroma that affects the quality and character of tea. To identify enzymes related to volatile organic compounds biosynthesis and their expression profiles during early stages of tea manufacturing process, transcriptome of tea shoots from six sampling points were sequenced using next generation RNA sequencing technology. After de novo assembly, a total of 222,087 contigs were aligned with known sequences. 29% of the contigs were annotated with gene name, open reading frame, and Gene Ontology terms. After reducing redundancy, 20,137 unigenes were obtained, with 1,237 unigenes differentially expressed during tea manufacturing process. There were 18 unigenes annotated to enzymes involved in the biosynthesis of volatile terpenes, volatile fatty acid derivatives and carotenoid derivatives. Alcohol dehydrogenase was the most up-regeleted gene during early stage of tea processing, and putative volatile terpene biosynthesis pathway in C. sinenesis was proposed. On the other hand, since β-primeverosides are the major forms of glycosidically bound volatiles precursors in tea, the sequence of β-primeverosidase was cloned with primers from RNA-seq results and expressed with E. coli, which can further be purified and had a potential to use as exogenous enzyme for aroma enhancement. This study provided novel insight into tea volatiles with the expression profile of related genes during manufacturing process, as well as potential approach to improve tea flavors.
Subjects
Camellia sinensis
semi-fermented tea
volatile organic compounds
RNA sequencing
terpene biosynthesis pathway
β-primeverosidase
Type
thesis
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