SA-responsive transcription factor GbMYB36 promotes flavonol accumulation in Ginkgo biloba

Flavonoids are abundant secondary metabolites in Ginkgo biloba and have a wide range of medicinal values. Salicylic acid (SA) can induce flavonoid accumulation in plants, but the detailed regulatory mechanism remains unclear. Here, we established the optimal media for ginkgo callus induction and subculture, and found that exogenous SA greatly increased the content of flavonol, including quercetin, kaempferol, isorhamnetin. Transcriptome changes in SA-treated calli showed that most structural genes involved in flavonoid biosynthesis were upregulated. Particularly, overexpression of GbF3'H in ginkgo calli significantly increased the content of flavonol, suggesting the vital role of GbF3'H in flavonoid biosynthesis. We further identified that a R2R3-MYB, GbMYB36, were significantly upregulated in SA treated calli. Transient overexpression and a LUC assay indicate that GbMYB36 act as an activator, and improve flavonoid biosynthesis through regulating the expression of GbF3'H. Our findings provide insight into the molecular basis of SA-induced flavonoid biosynthesis in ginkgo.