Identification and Functional Characterization of a Novel C -Glycosyltransferase from Euscaphis konishii Hayata and Its Role in C -Glycoside Biosynthesis

C-glycosylation is a critical modification in bioactive compounds to enhance structural stability and biological activity. In this study, a novel C-glycosyltransferase (CGT) gene EkCGT1, derived from Euscaphis konishii Hayata, a medicinal plant rich in chromones, was cloned and heterologously expressed. In vitro enzymatic assays demonstrated that EkCGT1 catalyzes the C-glycosylation of the chromone substrate noreugenin with UDP-glucose as the sugar donor, producing chromone C-glycosides Biflorin and Isobiflorin. To investigate its planta function, we generated E. konishii transgenic lines of overexpressing or silencing EkCGT1. Compared to RNAi lines, EkCGT1-OE plants exhibited larger leaves and expanded vascular bundles in both leaf veins and stems, along with significantly higher accumulation of chromone C-glycosides. These findings expand our understanding of plant CGTs and identify EkCGT1 as a promising candidate for the biosynthesis of stable C-glycosides, with potential applications in functional food and natural product development.