Journal of Tea Science Research, 2024, Vol.14, No.1, 1-9 http://hortherbpublisher.com/index.php/jtsr 2 Exploring the potential mechanisms by which microorganisms regulate catechin synthesis in tea plants at different levels is of great significance for optimizing tea quality and breeding functional tea cultivars. The quality of Biluochun tea is closely related to the microbial community in the soil, and the microorganisms on the surface of tea leaves may also play an important role in the catechin synthesis process. This study aims to systematically investigate the influence of microorganisms on catechin synthesis in Biluochun tea and explore the relationship between microbial community diversity, structure, and catechin content. By delving into the impact of microorganisms on catechin synthesis in Biluochun tea, we can gain a better understanding of the mechanisms underlying tea quality formation and provide scientific evidence for improving the quality of Biluochun tea. Moreover, a deeper understanding of the relationship between microorganisms and catechin biosynthesis may also offer insights for the optimization and improvement of other tea varieties, thereby promoting the development of the tea industry. 1 Impact of Microorganisms on the Growth and Development of Biluochun Tea Plants 1.1 Influence of mycorrhiza on tea plants To elucidate the microscopic mechanisms by which mycorrhiza enhance the root system of tea plants, this study employed real-time optical microscopy tracking of GFP-labeled Vesicular-arbuscular (VA). The results indicate that when the mycorrhiza penetrates the tea tree root cells, the hyphal surface first generates pressure, leading to a morphological change in the root cell membrane rupture (Zheng, 2010). Subsequently, the hypha branch out, forming a Y-shaped branching structure that expands into the intercellular and intracellular spaces of the surrounding roothair cells. This composite mode of "physical invasion + biological regulation" effectively increases the contact area and absorption capacity between the root system and the soil. To verify whether root system expansion is derived from plant gene expression regulation, plant transformation techniques were employed to introduce root-related genes into tea plants, and GFP signals were observed. The results demonstrated that after overexpression of the root-related genes, the structure of the tea plant root system changed, with increased density and branching evident. This provides a theoretical foundation for subsequent studies on the regulation of plant root system development by mycorrhiza from a systems biology perspective. 1.2 Impact of nitrogen-fixing bacteria on tea plants To further investigate the mechanisms by which nitrogen-fixing bacteria affect nitrogen nutrition in tea plants, this study collected the root systems and rhizosphere soil of Biluochun tea plants under different treatments. High-throughput 16S rRNA gene sequencing was employed to identify and quantify the microbial community composition in the roots and soil. The results demonstrated that the application of high-quality rhizobial nitrogen-fixing bacteria (Azotobacter) significantly increased the abundance of Pseudomonas in the root system of tea plants. Comparison of the number of bacteria in different soil and tea age (Figure 1). To further confirm the enrichment effect of the inoculant on soil microorganisms, this study utilized nitrogen isotope-labeled Azotobacter strains that were inoculated into a nitrogen-limited culture medium. Isotope incorporation rates were compared to determine the nitrogen-fixing efficiency of the selected high-quality strain, Az-3 (Wang, 2022). Subsequent genome sequencing revealed that Az-3 possesses a complete nitrogen-fixing gene cluster, which may contribute to its exceptional nitrogen-fixing capabilities. To observe the mechanism of action of the inoculant, a dual-culture system was employed to investigate the interaction between Az-3 bacteria and tea root cells. It was found that Az-3 can activate the calcium signaling pathway in the tea plant root system, leading to enhanced root growth and nitrogen uptake, possibly through the modulation of signaling molecules such as ACC levels. These findings provide novel insights for further research on the molecular regulation of nitrogen-fixing bacteria in plant nutrition.
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