Molecular Plant Breeding 2025, Vol.16, No.5, 278-286 http://genbreedpublisher.com/index.php/mpb 281 Figure 1 Distribution and analysis of editing sites and multi-elements inCamellia sinensis (Adopted from Li et al., 2023) Image caption: (A) Chromosome of the Camellia sinensis genome. (B-F) Density heatmap of the different element. (B) GC content; (C) Gene density; (D) GQ density; (E) SSR density; (F) PAM density; (G) Standardised fold plot of correlation of various elements in the 120~130 Mbp interval of chromosome 5 (Adopted from Li et al., 2023) 5.2 Promoter engineering for aroma biosynthetic pathway enhancement The expression of key genes in aroma-related metabolic pathways is regulated by promoters. Promoter engineering can enable target genes to be expressed more efficiently in specific tissues or developmental stages, enhancing the synthesis of aroma substances. The specific expression of terpene synthesization-related genes (such as the CsTPS family) and their alleles in tea plants is closely related to the formation of aroma. The optimization of promoter regulation is expected to achieve the directional accumulation of aroma components (Gu et al., 2023). Genome-wide and haplotype assembly studies have revealed the selected key genes in the aroma biosynthesis pathway, providing valuable targets for promoter engineering (Zhang et al., 2021). 5.3 Synthetic biology approaches for metabolic pathway optimization Synthetic biology can efficiently synthesize aroma and flavor substances by modularly reconstructing and optimizing metabolic pathways. There is multi-copy amplification and expression regulation of genes related to aroma and flavor substances (such as catechins, theanine, and caffeine) in tea plants, laying the foundation for the application of synthetic biology (Wang et al., 2021b). By integrating multi-gene expression, metabolic flow redirection and regulatory element optimization, it is expected to increase the yield and variety of target metabolites. Synthetic biology can also utilize heterologous expression systems to analyze and reconstruct the functions of aroma-related enzymes in tea plants, providing theoretical and technical support for molecular breeding (Zhou et al., 2017). 6 Environmental and Agronomic Interactions 6.1 Effects of terroir factors (altitude, soil, climate) on flavor profiles Terroir factors, such as altitude, soil type and climatic conditions, have a significant impact on the accumulation of flavor substances in tea trees. Different geographical environments can cause significant differences in the content of secondary metabolites (such as catechins, amino acids, and terpenoids) in tea, which in turn determine the aroma and flavor characteristics of tea. For instance, some tea tree groups can accumulate more polyphenols and aromatic substances in high-altitude areas. Low temperature and light changes can also regulate the expression of flavor-related genes (Yu et al., 2020; Zhao et al., 2022). In addition, supplementing trace elements (such as selenium) in the soil can enhance the freshness and aroma of tea by regulating amino acid and flavonoid metabolic pathways (Zhang et al., 2025). The interaction between these terroir factors and genetic background is an environmental variable that needs to be given key consideration in molecular breeding.
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