Integrated metabolomic and transcriptomic analysis provides insights into the flavonoid formation in different Glycyrrhiza species

Medicinal licorice is obtained from the roots and rhizomes of three species, Glycyrrhiza inflata, G. glabra, and G. urelensis. Previous studies have reported chemical differences among these species, but the detailed composition of specialized metabolites and the underlying molecular basis for the formation of characteristic compounds remain unclear. Here, we performed integrated metabolic and transcriptomic analysis to identify the characteristic flavonoids (CFs) of these three licorice species as well as the key regulators of their biosynthesis. A total of 866 metabolites including 251 flavonoids were identified. Among them, 71 flavonoids were differentially accumulated in three licorice species. Transcriptome analysis showed that a set of the structural genes involved in CF biosynthesis were differentially expressed among the three licorice species. In addition, weighted gene co-expression network analysis (WGCNA) was used to construct a regulatory network for CF biosynthesis. A candidate transcription factor GibHLH69 was proved to promote GiCHS20 expression and contribute to the accumulation of multiple CFs in G. inflata. These results provide valuable information for further understanding the biosynthesis of CFs and future breeding of Glycyrrhiza varieties.