Journal of Tea Science Research, 2024, Vol.14, No.3, 169-181 http://hortherbpublisher.com/index.php/jtsr 175 6.3 Nerolidol in tea Nerolidol is a sesquiterpenoid alcohol that adds a woody and floral note to tea. The biosynthesis of nerolidol involves the MVA pathway, which is responsible for the production of sesquiterpenoids. Although specific studies on nerolidol biosynthesis in tea are limited, it is known that the withering process can enhance the metabolism of terpenoids, potentially increasing the content of nerolidol in tea leaves (Wang et al., 2019). Additionally, the regulatory relationship between miRNAs and the biosynthesis of volatile compounds, including nerolidol, suggests that miRNAs may play a crucial role in modulating its levels in different tissues of the tea plant (Li et al., 2021). The biosynthesis of linalool, geraniol, and nerolidol in tea is influenced by both genetic factors and manufacturing processes. The MVA and MEP pathways play a central role in the production of these terpenoids, while miRNAs and specific manufacturing steps can modulate their levels, thereby affecting the flavor profile of tea. 7 Genetic and Environmental Factors 7.1 Influence of genetic variability on tea metabolites Genetic variability plays a crucial role in the biosynthesis of secondary metabolites in tea plants. Different tea cultivars exhibit distinct metabolic profiles, which are influenced by their genetic makeup. For instance, a study on 100 tea plant cultivars revealed that genetic factors significantly affect the composition of microbiomes in different plant compartments, such as the rhizosphere, root endosphere, and phyllosphere. Specific genes related to cell wall and carbon catabolism were linked to root endosphere microbial composition, while genes associated with metal ion metabolism influenced rhizosphere microbiomes (Tan et al., 2022). Additionally, MYB transcription factors have been identified as key regulators of secondary metabolite biosynthesis, including flavonoids, caffeine, and theanine, in tea plants. These transcription factors also play roles in shoot development and stress responses, further highlighting the genetic control over metabolite production (Li et al., 2022). Furthermore, the age of tea plants can influence metabolite profiles, with older plants showing upregulated flavonoid biosynthesis due to differential gene expression (Yue et al., 2022). These findings underscore the importance of genetic variability in determining the quality and composition of tea metabolites. 7.2 Environmental impacts on tea metabolite production Environmental factors significantly impact the production of secondary metabolites in tea plants. Climate change, including shifts in seasonality, water stress, and temperature variations, can lead to substantial changes in metabolite concentrations. For example, a systematic review found that seasonality and water stress consistently affected phenolic compound levels, with seasonal shifts often resulting in decreased concentrations and drought stress leading to increased levels. Geographic factors also play a role, as the metabolome of tea plants varies with location, climate, and cultural practices. Multivariate statistical analysis has shown strong correlations between environmental factors and the levels of theanine and catechin derivatives in teas from different regions (Lee et al., 2018). Additionally, stress conditions such as cold, drought, and intense light can alter the profiles of primary and secondary metabolites, affecting tea quality. Controlled stress exposure during tea manufacturing has been proposed as a strategy to enhance tea quality by inducing the production of specific volatile compounds (Shao et al., 2021). These studies highlight the complex interplay between environmental conditions and tea metabolite production. 7.3 Interaction between genetics and environment in tea plants The interaction between genetic factors and environmental conditions is crucial in shaping the metabolite profile of tea plants. Genetic determinants can influence the tea plant's response to environmental stresses, thereby affecting the accumulation of metabolites. Fang et al. (2021) through genome-wide association analysis (GWAS), studied molecular markers of important secondary metabolites related to tea flavor (such as theanine, caffeine, and catechins) in tea plants. These secondary metabolites play a key role in the formation of tea flavor and have high heritability. The study results showed that the content of these metabolites varied significantly across different seasons and exhibited considerable genetic diversity among different tea plant varieties (Table 1). These findings not only reveal the genetic mechanisms of secondary metabolites in tea plants but also provide theoretical basis
RkJQdWJsaXNoZXIy MjQ4ODYzNA==