Identification and characterization of thirteen gene families involved in flavonoid biosynthesis in Ginkgo biloba

Ginkgo biloba leaves are rich in medicinal compounds, which constitute the raw materials of G. biloba extract (GBE). GBE is known for its outstanding curative effects in the treatment of cardiovascular and cerebrovascular diseases, and is widely used in clinical medicine. Flavonoids are the primary components of GBE and determine the medicinal value of leaves. However, the copy numbers, characteristics, and expression patterns of genes involved in G. biloba flavonoid biosynthesis are unclear. Here, we identified 13 gene families in the G. biloba flavonoid biosynthesis pathway, and obtained 111 enzyme genes. The flavonoid biosynthesis-related genes of G. biloba have high copy numbers and are clustered on chromosomes. In addition, multiple genes contain ultra-large introns. The promoters of the 111 enzyme genes contain elements that respond to light, as well as multiple hormone-related elements and stress response elements. These genes were also confirmed to be induced by hormones, ultraviolet B (UV-B), and drought stress by real-time quantitative PCR. Subcellular localization experiments showed that the GbCHS9 and GbC4H4 proteins were localized in the cytoplasm, nucleus, and cell membrane. Degradome data analysis confirmed that 10 miRNAs targeted four genes. In summary, we identified and characterized 13 gene families involved in flavonoid biosynthesis in G. biloba and revealed some unique features not found in angiosperms. The results of this study provide a basis for further investigation of the genes regulating G. biloba flavonoid biosynthesis.