Identification and Characterization of Two Bibenzyl Glycosyltransferases from the Liverwort Marchantia polymorpha .

Liverworts are rich in bibenzyls and related O -glycosides, which show antioxidant activity. However, glycosyltransferases that catalyze the glycosylation of bibenzyls have not yet been characterized. Here, we identified two bibenzyl UDP-glucosyltransferases named Mp UGT737B1 and Mp UGT741A1 from the model liverwort Marchantia polymorpha . The in vitro enzymatic assay revealed that Mp UGT741A1 specifically accepted the bibenzyl lunularin as substrate. Mp UGT737B1 could accept bibenzyls, dihydrochalcone and phenylpropanoids as substrates, and could convert phloretin to phloretin-4- O -glucoside and phloridzin, which showed inhibitory activity against tyrosinase and antioxidant activity. The results of sugar donor selectivity showed that Mp UGT737B1 and Mp UGT741A1 could only accept UDP-glucose as a substrate. The expression levels of these Mp UGTs were considerably increased after UV irradiation, which generally caused oxidative damage. This result indicates that Mp UGT737B1 and Mp UGT741A1 may play a role in plant stress adaption. Subcellular localization indicates that Mp UGT737B1 and Mp UGT741A1 were expressed in the cytoplasm and nucleus. These enzymes should provide candidate genes for the synthesis of bioactive bibenzyl O -glucosides and the improvement of plant antioxidant capacity.