[Diversity of endophytes in licorice from different habitats based on metagenomics and analysis of their correlation with accumulation of active ingredients].

Abstract

Licorice is an important TCM. Its medicinal quality mainly depends on the accumulation of active ingredients such as flavonoids(such as liquiritin and isoliquiritin) and triterpenoids(such as glycyrrhizic acid), and the endogenous microbial community is considered an important environmental factor influencing the synthesis of these components. To analyze the regulatory effect of endophytes on secondary metabolites of licorice, metagenomic sequencing and ultra-high performance liquid chromatography were used to compare and analyze the composition and function of endophytes in wild and cultivated licorice roots as well as their relationship with the main active ingredients. The results showed that the content of liquiritin, isoliquiritin, and glycyrrhizic acid in wild licorice was significantly higher than that in cultivated licorice. The metagenomic analysis annotated that the endophytes in wild licorice belonged to 31 phyla and 315 genera, while those in cultivated licorice belonged to 24 phyla and 125 genera. Among them, Rathayibacter, Plantibacter, and other genera were significantly enriched in wild licorice, while only Lysobacter was significantly enriched in cultivated licorice. Functional annotations indicated that the endophytes in wild licorice were enriched in pathways such as two-component systems, nitrogen metabolism, and aminoacyl tRNA synthesis, while those in cultivated licorice were enriched in pathways such as photosynthesis and carbon fixation. Further correlation analysis revealed that some endophyte genera(such as Phenylobacterium and Microbacterium) and functional pathways(such as signal transduction and terpenoid metabolism) were significantly positively correlated with the content of glycyrrhizic acid and liquiritin. In addition, the abundance of glycosyltransferases and cytochrome P450 in endophytes in wild licorice was significantly higher than that in cultivated licorice. This indicated that they had an enzymatic basis for participating in the synthesis of host glycosides. This research systematically reveals the differences in endophytic community structure, function, and accumulation of active ingredients between wild and cultivated licorice, providing a theoretical basis for understanding the microbial mechanism of endophytes regulating the quality of licorice, and also offering references for developing microbial fertilizers to improve the quality of licorice.