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

<i>C</i>-glycosylation is a critical modification in bioactive compounds to enhance structural stability and biological activity. In this study, a novel <i>C</i>-glycosyltransferase (CGT) gene EkCGT1, derived from <i>Euscaphis konishii</i> Hayata, a medicinal plant rich in chromones, was cloned and heterologously expressed. In vitro enzymatic assays demonstrated that EkCGT1 catalyzes the <i>C</i>-glycosylation of the chromone substrate noreugenin with UDP-glucose as the sugar donor, producing chromone <i>C</i>-glycosides Biflorin and Isobiflorin. To investigate its planta function, we generated <i>E. konishii</i> 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 <i>C</i>-glycosides. These findings expand our understanding of plant CGTs and identify EkCGT1 as a promising candidate for the biosynthesis of stable <i>C</i>-glycosides, with potential applications in functional food and natural product development.