Functional Analysis of GbFLS1045 Regulating the Metabolism of Flavonoids in Ginkgo biloba L.

<b>Objectives</b>: Flavonoids are a class of widely distributed secondary metabolites in plants. <i>Ginkgo biloba</i> leaves are rich in flavonoids and thus are utilized for extracting medicinal components to treat and prevent cardiovascular and cerebrovascular diseases. Flavonol synthase (FLS) serves as a key enzyme in the flavonol metabolic pathway. Numerous studies have identified and characterized FLS family genes across various plant species, all of which play crucial roles in regulating the flavonoid biosynthetic pathway. <b>Methods</b>: We measured the flavonoid content in <i>Ginkgo biloba</i> leaves across different months, performed transcriptomic analysis on leaves from months showing an increasing trend, and screened out the <i>GbFLS1045</i> gene involved in the synthesis of the FLS enzyme. Molecular biology techniques were then employed to explore the function of the <i>GbFLS1045</i> gene. <b>Results</b>: From June to August, the flavonoid content in <i>Ginkgo biloba</i> leaves exhibited an upward trend, and we found that <i>GbFLS1045</i> is localized in the cytoplasm, cell membrane, and nucleus through transient transformation in <i>Nicotiana tabacum</i>. Overexpression(OE) of <i>GbFLS1045</i> in <i>Arabidopsis thaliana</i> resulted in significantly higher levels of total flavonol glycosides, kaempferol, quercetin, and isorhamnetin in OE transgenic plants compared to WT controls. Furthermore, in OE lines of <i>Ginkgo biloba</i> callus, the isorhamnetin content was consistently elevated relative to both WT and Anti lines. <b>Conclusions</b>: <i>GbFLS1045</i> positively regulates flavonoid synthesis in <i>Ginkgo biloba</i>.