Dissection of the general two-step di- <i>C</i> -glycosylation pathway for the biosynthesis of (iso)schaftosides in higher plants

Abstract

Significance Schaftoside and isoschaftoside are important plant defense chemicals and bioactive natural products widely present in higher plants. Although a number of plant CGTs have been reported, we know very little about the CGTs catalyzing the biosynthesis of flavonoid di- C -glycosides with different sugar residues. Here we reveal the biosynthesis of (iso)schaftosides in plants is sequentially catalyzed by a pair of homologous but functionally different enzymes (CGTa and CGTb). Crystal structure analysis and key amino acids mutagenesis could switch the function of SbCGTb to SbCGTa. We further reveal this pathway is general for higher plants. Our results provide a platform to efficiently synthesize (iso)schaftosides and to understand their plant defense mechanisms.