Combined Analysis of Transcriptome and Small RNA Sequencing Reveals the Mechanism of UV-B-promoted Flavonoid Biosynthesis in Ginkgo biloba

Flavonoids are the most abundant medicinal ingredients in Ginkgo biloba L. leaf extract (GBE), which is an important industrial raw material for the treatment of cardiovascular and cerebrovascular diseases. Our previous study found significantly higher flavonoid content in G. biloba leaves treated with UV-B for 7 days. However, the molecular mechanisms by which the miRNA-mRNA network responds to UV-B irradiation and regulates flavonoid biosynthesis remain unclear. Here, we identified 1348 differentially expressed genes (DEGs) by transcriptome sequencing of G. biloba leaves from UV-B treatment at 0 (CK) and 7 days, and 89.76% of DEG were induced by UV-B irradiation. Analysis of the flavonoid biosynthesis pathway revealed 16 differentially expressed structural genes (SGs), all of which were upregulated after UV-B treatment. Twelve DEGs were identified by analyzing transcription factors (TFs), including MYB, bHLH, and WD40, which regulate flavonoid biosynthesis, 11 of which were upregulated. Furthermore, small RNA sequencing of ginkgo leaves from control and UV-B-treated groups on days 0 and 7 revealed 58 differentially expressed miRNAs (DEMs). KEGG enrichment analysis showed that the target genes of the DEMs were significantly enriched in the flavonoid biosynthesis pathway. Finally, combined analysis of transcriptome and miRNA data identified 32 DEMs targeting 43 SGs involved in flavonoid biosynthesis, and 42 DEMs targeting 68 TFs that regulate flavonoid biosynthesis. Taken together, our findings revealed that multiple miRNA-SG and miRNA-TF networks may regulate G. biloba flavonoid biosynthesis in response to UV-B irradiation, providing new insights into the miRNA regulation of G. biloba flavonoid biosynthesis.