Journal of Tea Science Research, 2024, Vol.14, No.6, 322-334 http://hortherbpublisher.com/index.php/jtsr 325 other secondary metabolism-related gene families are jointly influenced by natural selection and artificial domestication, thus forming a diverse aroma spectrum (Wang et al., 2021). Aroma markers of specific varieties are derived from their unique genetic background, allelic differences, and complex regulatory mechanisms. For example, the aroma of jasmine flowers in the "Chungui" variety is due to the synergistic effect of increased chromatin accessibility and DNA demethylation, which upregulates the expression of key aroma synthesis genes during processing (Li et al., 2024b). Similarly, QTL mapping and metabolome-wide association analysis have identified multiple specific genes and allelic variants associated with the accumulation of characteristic volatiles (Chen et al., 2023a; Gu et al., 2023). 4 Genetic Regulation of Aroma Biosynthesis in Tea 4.1 Structural genes involved in aroma biosynthesis The biosynthesis of key aroma components in tea is mainly regulated by several structural gene families. Among them, terpene synthase (TPS) is the core enzyme for the synthesis of monoterpenes and sesquiterpenes, which gives tea its typical floral and fruity aroma. The expansion and diversification of the TPS gene family in high-aroma varieties such as "Huangdan" is the genetic basis for its rich volatile spectrum (Wang et al., 2021; Qiao et al., 2022; Gu et al., 2023). The lipoxygenase (LOX) gene family plays a key role in the production of fatty acid-derived aroma substances. The products, such as green leaf volatiles and jasmonic acid, not only have aroma characteristics, but also participate in plant defense mechanisms (Lin et al., 2024; Zhou et al., 2024). The phenylalanine ammonia lyase (PAL) gene is the starting enzyme in the phenylpropanoid metabolic pathway, catalyzing the production of phenylpropanoid aroma components such as phenylethanol and benzaldehyde (Gu et al., 2023; Gao et al., 2023). Comparative genomics and transcriptome studies have shown that different tea varieties have large differences in the expression of aroma structural genes. In high-aroma varieties, such as "Huangdan" and "Jinguanyin", the expression of the TPS gene is upregulated, and there is allelic variation, resulting in an increase in the content of floral and fruity volatiles (Wang et al., 2021; Gu et al., 2023; Gao et al., 2023). Key genes in metabolic pathways, like MEP, MVA, LOX and shikimic acid often show allele-specific expression (ASE), which is one of the important reasons for the formation of variety-specific aroma spectra (Gu et al., 2023). Environmental factors and stress during processing (such as withering and mechanical damage) will further regulate the expression of these structural genes and promote the dynamic accumulation of aroma components (Zeng et al., 2019; Qiao et al., 2022; Lin et al., 2024). 4.2 Transcriptional regulation networks of aroma traits Transcription factors (TFs), such as MYB, bHLH, WRKY, NAC and ERF, play a key role in regulating the expression of structural genes related to aroma synthesis (Wei et al., 2023; 2024; Yue et al., 2025). These transcription factors can recognize and bind to cis-acting elements in the promoters of structural genes (e.g., TPS, LOX and PAL), thereby regulating their transcriptional activity according to developmental signals or environmental stimuli. For example, MYB and bHLH transcription factors can form complexes to jointly activate or inhibit terpenoid synthesis, while WRKY and ERF factors are mostly involved in aroma regulation pathways under stress conditions (Huang et al., 2024; Li et al., 2024a). Tea variety-specific aroma traits are often determined by genetic variation in transcription factor binding sites and allelic differences in regulatory genes. Variations in the promoter region of key TPS genes and differences in the expression of MYB, bHLH and WRKY transcription factors in different varieties are important reasons for the unique aroma spectra of oolong tea and jasmine-flavored tea (Wang et al., 2021; Li et al., 2024a; Yue et al., 2025). Multi-omics studies and QTL positioning analysis have screened out a series of candidate regulatory modules and key transcription factors that are involved in regulating the differential accumulation of aroma substances in different tea varieties (Chen et al., 2023a; Chai et al., 2023; Gao et al., 2023) (Figure 1).
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