Comprehensive analysis of bHLH gene family provides insights into GibHLH13 regulating glycyrrhizin biosynthesis by integrating jasmonate signaling in Glycyrrhiza inflata

Glycyrrhiza inflata Batal. is a highly valued medicinal licorice plant known for its potent anti-inflammatory and hepatoprotective properties and glycyrrhizin is the most popular active ingredient. The jasmonic acid (JA) signaling pathway plays key roles in regulating the biosynthesis of multiple secondary metabolites. bHLH transcription factors are important regulators in JA signaling pathways as well as biosynthesis of secondary metabolites. Here we confirmed the promoting effects of JA on glycyrrhizin accumulation and conducted a comprehensive analysis of GibHLH genes in G. inflata . A total of 184 GibHLH genes were identified in the genome, and their protein physicochemical properties, phylogenetic relationships, and chromosome locations were characterized. Among these, a JA-induced gene GibHLH13 emerged as a positive regulator of the expression of glycyrrhizin biosynthesis genes such as Giβ-AS , GiCYP72A154 , and GiCSyGT . We also showed that GibHLH13 activates Giβ-AS expression by directly binding to the E-box of its promoter region. Additionally, we identified 7 MeJA-responsive GiJAZs that interact with GibHLH13. Among them, the inhibitory effect of GiJAZ9 on GibHLH13 activity was analyzed. Overall, our study identifies the GibHLH and GiJAZ gene families in G. inflata and elucidates the molecular mechanism by which GiJAZ9-GibHLH13 complex regulating glycyrrhizin biosynthesis at the transcriptional level. • Glycyrrhiza inflata is a highly valued medicinal licorice and the accumulation of glycyrrhizin is positively regulated by jasmonate (JA). • A total of 184 GibHLH genes were identified in the G. inflata genome and a JA-induced gene GibHLH13 functions as a positive regulator of the expression of glycyrrhizin biosynthesis genes. • GibHLH13 activates Giβ-AS expression by directly binding to the E-box. • Among the 7 JA-responsive GiJAZs that interact with GibHLH13, GiJAZ9 suppresses the expression of glycyrrhizin biosynthesis genes by inhibiting GibHLH13 activity.