Functional Characterization of CsGT3 in the Biosynthesis of ( Z )-3-Hexenyl Disaccharides, Anti-Herbivore Metabolites in Tea Plants ( Camellia sinensis )

Our previous study demonstrated that (Z)-3-hexenyl vicianoside and (Z)-3-hexenyl primeveroside display antiherbivore activity against tea gray geometrids, yet their biosynthetic glycosyltransferases (GTs) remained uncharacterized. Here, we identified CsUGT91A1 (CsGT3) from tea plants, which localizes to the cytoplasm and nucleus. Recombinant CsGT3 converted (Z)-3-hexenyl glucoside into vicianoside and primeveroside, with optimal activity at 30 °C and pH 7.5. Kinetic and docking studies indicated higher catalytic efficiency for UDParabinose than UDPxylose. Transient overexpression in tobacco and tea plants confirmed CsGT3 catalyzes this conversion. Moreover, infestation by tea green leafhoppers, tea gray geometrids, or tea aphids consistently increased the accumulation of (Z)-3-hexenyl glycosides, associated with the increased precursor (Z)-3-hexenol. These findings elucidate the role of CsGT3 in the biosynthesis of (Z)-3-hexenyl disaccharides and enhance the understanding of volatile glycoside metabolism in tea plants.