Mechanism of Melatonin Promotion of Flavonoid Biosynthesis in Ginkgo biloba

Ginkgo biloba leaves are rich in flavonoids and have significant medicinal value. Exogenous hormones can affect flavonoids biosynthesis, but as a novel hormone, the effect of melatonin on G. biloba flavonoids biosynthesis is unclear. To investigate the potential role of melatonin in the synthesis of G. biloba flavonoids, we conducted an experiment in which G. biloba seedlings were treated with eight different concentrations of melatonin. We harvested the leaves after 1, 7, 14, and 21 days and measured the total flavonoid content. The results showed that the flavonoid levels increased most significantly in the G. biloba leaves treated with 100 μmol/L melatonin for 7 days. Based on these findings, we selected the treatment group and the control group for transcriptome sequencing. Through differential expression analysis, we identified 1673 differentially expressed genes, of which 778 up-regulated genes and 895 down-regulated gene. Further analysis using KEGG enrichment analysis indicated that the upregulated differentially expressed genes were enriched in the flavonoid biosynthesis pathway. Finally, we further confirmed through real-time quantitative PCR that melatonin might enhance the biosynthesis of G. biloba flavonoids by increasing the expression of structural genes associated with flavonoid biosynthesis (such as 4CL, F3 'H and ANR) and transcription factors involved in flavonoid regulation (including bZIP, bHLH and MYB). This study preliminarily revealed the molecular mechanism by which melatonin regulates G. biloba flavonoid biosynthesis through transcriptome sequencing, laying a theoretical foundation for the application of melatonin.