Metabolomics analysis reveals crucial effects of arbuscular mycorrhizal fungi on the metabolism of quality compounds in shoots and roots of Camellia sinensis L

Arbuscular mycorrhizal fungi (AMF) are known as plants' mutualists to enhance plant growth, but their impact on the quality-related metabolites in Camellia sinensis still needs to be studied. In this study, the 2-year-old potted C. sinensis cv. 'Longjing 43' was inoculated with AMF Rhizophagus irregularis to examine the effect of AMF colonization for 3 months on plant growth, photosynthesis, and changes in metabolomics and associated gene expression in the shoots and roots of tea plants. The results showed that AMF not only promoted the growth of tea plants but also significantly up-regulated the total contents of flavonoids and free amino acids, especially the anthocyanins, flavanols, GABA, and arginine. Consistently, the expression of genes such as F3H, DFR, LAR, ANR, UFGT, GDH, and GS in tea shoots was induced by AMF. Further studies found that transcription factors MYBs and HY5, as well as phytohormone strigolactones, were induced by AMF, which may participate in the regulatory mechanism controlling the metabolism of tea-quality compounds. These findings revealed regulatory mechanisms through which AMF affected tea quality and provided a theoretical basis for the application of AMF in tea gardens to improve the economic value and health benefits of tea.