Identification and Characterization of a novel flavonol synthases from Ginkgo biloba.

Abstract Context Flavonoids are regarded as important components in the extract of Ginkgo biloba leaf (EGB) and related medicinal preparations. Flavonol synthases (FLS) is a crucial gene involved in flavonoid biosynthesis. Objective In the current study, the differentially expressed genes (DEGs) of the flavonoid biosynthesis pathway were analyzed by comparing the transcriptome data of Ginkgo biloba leaves harvested at different months from 2-year-old nursery leaves and 20-year-old trees. Subsequently, Gb_14024, a novel FLS member named GbFLS2, was cloned and its bioinformatics and functional characteristics were further explored. Materials and methods Full-length GbFLS2 cDNA (GenBank accession No. MW201964) contained a 1017bp open reading frame that encoded 338 amino acids. The genomic sequence of GbFLS2 contains three exons and two introns. Bioinformatic analysis showed that GbFLS2 belongs to the 2-oxoglutarate iron-dependent oxygenase family. The cis-element analysis of the GbFLS2 upstream predicted that GbFLS2 might be regulated by abscisic acid (ABA), gibberellin acid (GA), salicylic acid (SA), light, low-temperature, hypoxic conditions, drought, and MYB Transcription factors (TFs). Expression profiling analysis revealed that GbFLS2 expression waved with the month in 2-year-old nursery leaves and 20-year-old trees, and reached a peak in June in 2-year-old nursery leaves. Results The recombinant protein was successfully expressed and purified. Discussion and conclusions The recombinant protein catalyzed the conversion of kaempferol and quercetin from dihydrokaempferol and dihydroquercetin, respectively, in vitro.