Journal of Tea Science Research, 2024, Vol.14, No.1, 1-9 http://hortherbpublisher.com/index.php/jtsr 5 Some studies have found that the species and abundance of soil microorganisms are positively correlated with the content of catechins in tea. Some soil microorganisms can secrete specific enzymes, such as tannase and catechin oxidase, which can participate in the synthesis and metabolism of catechin (Wei et al., 2023). At the same time, the activities of soil microorganisms can also affect the content of trace elements in tea, and then affect the synthesis and stability of catechins. The microbial community inside tea is also closely related to the composition and content of catechins, and the microbial community inside tea affects the synthesis and transformation process of catechins mainly through metabolic activities (Tan et al., 2009). Some microorganisms can decompose catechins into low-polymerization compounds, such as catechin dimers and trimers, which play an important role in the fermentation and processing of tea. 3 Impact of Microorganisms on Catechin Accumulation in Biluochun Tea 3.1 Influence of endophyte To delve into how Pseudomonas promotes the biosynthesis of catechins in tea plants, high-throughput RNA sequencing technology was employed to comparatively analyze the transcriptome of tea leaves after symbiosis with Pseudomonas bacteria. The results revealed that Pseudomonas significantly upregulates the expression of key catechin biosynthesis genes, such as PAL, C4H, and 4CL, in tea leaves. In order to verify whether this is achieved through the secretion of bioactive substances, the fermentation products of Pseudomonas B10 strain were identified by GC-MS and NMR. It was found that the B10 strain can efficiently secrete a key growth hormone named Smf (Pu et al., 2022). It was further confirmed by biotechnological means that Smf could specifically activate MAPK and Ca2+ signal transduction pathways in tea leaf cells. The levels of EC and EGCG in tea leaves were detected by HPLC after B10 strain was implanted into tea leaves. The results showed that the Smf of B10 bacteria could significantly increase the content of EC and EGCG by 15% and 20% respectively by activating MAPK and Ca2+ signals. Furthermore, the key transcriptional regulatory genes of Smf in activating the catechin biosynthesis pathway in tea leaves were identified using the homologous transcription factor Chip-seq technique. This provides a new perspective for future research on transcriptional regulation. 3.2 Influence of soil microorganisms in tea garden To investigate the impact of different soil microorganisms on catechin accumulation in tea plants, this study collected representative soil samples from four tea gardens (Wang et al., 2016). High-throughput 16S rRNA sequencing analysis revealed that Actinobacteria, a group of beneficial soil microorganisms, accounted for up to 38% of the microbial community in high-quality soil samples. To observe the presence of Actinobacteria in the soil, cathode ray microscopy was employed, and it was found that Actinobacteria primarily grow in clusters around soil pores and plant roots. Additionally, satellite positioning and soil genomics techniques were utilized to create distribution maps of Actinobacteria in the region. In order to further confirm its promoting effect, the strain SP-2 was identified by metagenome analysis, and it was found to have rich clusters of secondary metabolism genes. Then SP-2 bacteria were introduced into four representative soils for tea tree tests. The results showed that the EC content of tea leaves in SP-2 application group was significantly increased by 18%. This provides a reference for the subsequent regulation of soil quality and improvement of tea plant function from the microorganisms themselves. 4 Recent Research Advances 4.1 Studies on the impact of microorganisms on catechin synthesis in Biluochun Tea In recent years, there has been increasing research on the influence of microorganisms on catechin synthesis in Biluochun tea. Studies have indicated a close correlation between the types and abundance of microbial communities and the synthesis and content of catechins in Biluochun Tea. Both the microorganisms in tea
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