Comparative Transcriptome and Metabolome Analyses Revealed Quality Difference between Beauty Tea Processed through Indoor Withering and Outdoor Solar Withering.

Abstract

Withering is the first processing procedure of beauty tea, and there are few reports on the impact of withering methods on the quality of beauty tea and its regulatory mechanisms. Through comparison of fresh tea leaves (FT) with the leaves at Indoor natural Withering 18h (IWT-18) and Outdoor Solar Withering 6h (OWT-6), which were collected at the end of the two withering processes, 17282 and 13984 differentially expressed genes (DEGs) were screened and 267 and 154 differential metabolites (DMs) were identified, respectively. Coexpression network revealed that a large number of DEGs and DMs were enriched in phenylpropanoid, flavonoid, and adenosine Triphosphate binding (ABC) transporter pathways, and the number of DMs and DEGs in IWT-18 vs FT exceeded that in OWT-6 vs FT. Both withering methods promoted a significant increase in content of phenylalanine and upregulation of β-glucoside (BGLU) expression in the phenylpropanoid metabolism pathway. The five proanthocyanidins related to theaflavins in the flavonoid synthesis pathway was more significant accumulation in FT vs IWT-18 than in FT vs OWT-6. Meanwhile, both withering methods can affect the ABC transporter pathway to promote the accumulation of amino acids and their derivatives, but different withering methods affect different ABC transporter families. Outdoor withering with more severe abiotic stress has a greater impact on the ABCG family, while indoor withering has a more significant effect on the ABCC family. Sensory evaluation results showed that the dry tea of IWT-18 was slightly better than that of OWT-6 because of longer withering time and more thorough substance transformation. In conclusion, the formation of honey flavor in beauty tea may be closely related to the DEGs and DMs in these three pathways. Our research provides theoretical data support for further revealing the mechanism of quality formation during the withering process of beauty tea. This article is protected by copyright. All rights reserved.