Journal of Tea Science Research, 2024, Vol.14, No.6, 322-334 http://hortherbpublisher.com/index.php/jtsr 326 Figure 1 Multivariate statistical analysis of volatile components of seven tea cultivars. (a) Phenotypes of one bud and two leaves and their suitability. (b) PCA principal component analysis. (c) Types and relative contents of volatile components. (d) Proportions of volatile components (Adopted from Gao et al., 2023) Image caption: The figure presents the phenotypic traits of seven major tea cultivars, the principal component analysis (PCA) of volatile compounds, the types and relative contents of various aroma components, and the proportional composition of key volatile constituents. The PCA results indicate significant differences in aroma metabolic profiles among the cultivars, with particularly large variations observed in ‘Jinxuan’, ‘Baihaozao’, and ‘Tieguanyin’. These findings confirm the diversity in volatile composition across tea cultivars and provide data support for further studies on the underlying causes of these differences (Adapted from Gao et al., 2023) 4.3 Epigenetics and miRNA in aroma regulation Epigenetic modifications, especially DNA methylation, play an important role in regulating the expression of aroma biosynthesis genes. Hypomethylation (demethylation) of the promoter region can increase chromatin accessibility, thereby activating the expression of key aroma genes during tea processing or stress conditions (Yang et al., 2021; Kong et al., 2023; Li et al., 2024b; Yue et al., 2025). For example, the “Chungui” variety develops a jasmine scent during processing, and the promoter regions of its aroma-related genes show enhanced chromatin accessibility and decreased methylation levels, leading to significant expression of key genes (Li et al., 2024b). The dynamic changes in DNA methylation are also involved in regulating the accumulation of key aroma substances such as indole during postharvest stress (Yang et al., 2021; Kong et al., 2023). MicroRNAs (miRNAs) regulate aroma synthesis at the post-transcriptional level by targeting the mRNAs of TPS, LOX, and other structural genes (Zhao et al., 2018; Zhu et al., 2020). miRNAs and transcription factors form a regulatory network that synergistically controls the content of terpenoids and fatty acid-derived volatiles, allowing aroma components to be dynamically regulated under different developmental stages and environmental conditions. Specific miRNAs, have been shown to regulate the expression of transcription factors (like MYC2), thereby affecting the expression of downstream aroma synthesis genes and the activity of metabolic pathways. 5 Comparative Genomics and Aroma Traits in Tea Varieties 5.1 Genome-wide distribution of aroma-related genes Comparative genomics has revealed extensive genetic diversity in tea, with large numbers of single nucleotide polymorphisms (SNPs) and insertions/deletions (InDels) identified across cultivars. For example, phased
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