Camellia sinensis var. sinensis Transcriptome or Gene expression
The primary purpose of applying transcriptomics to black tea fermentation is to systematically reveal the gene expression dynamics that govern the enzymatic oxidation process, which directly determines tea quality. This approach is highly relevant because traditional biochemical analyses measure only end products or enzyme activities, whereas transcriptomics captures the upstream regulatory landscape. Specifically, by profiling mRNA changes across fermentation stages (withering, rolling, and oxidation), researchers can identify differentially expressed genes encoding key enzymes such as polyphenol oxidases, peroxidases, and glycosidases. This helps explain how catechins are converted into theaflavins and thearubigins, the pigments responsible for liquor color and mouthfeel. Furthermore, transcriptomics uncovers the activation of stress-related transcription factors (e.g., MYB, WRKY, bHLH) in response to mechanical injury and dehydration, which in turn regulate the biosynthesis of volatile aroma compounds like terpenes and fatty-acid derivatives. Correlating these transcriptional changes with metabolite profiles builds a causal chain from gene expression to final flavor characteristics. Another critical relevance is the discovery of molecular markers that indicate optimal fermentation endpoints, enabling precise process control and reducing batch-to-batch variation. Ultimately, the purpose is to provide a systems-level understanding of how genetic and processing factors shape tea quality, guiding marker-assisted breeding of elite tea varieties and the development of intelligent fermentation technologies. Without such transcriptomic insights, the complex molecular network underlying black tea fermentation would remain a "black box," limiting innovation in both cultivation and manufacturing.