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

Abstract

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 MpUGT737B1 and MpUGT741A1 from the model liverwort Marchantia polymorpha. The in vitro enzymatic assay revealed that MpUGT741A1 specifically accepted the bibenzyl lunularin as substrate. MpUGT737B1 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 MpUGT737B1 and MpUGT741A1 could only accept UDP-glucose as a substrate. The expression levels of these MpUGTs were considerably increased after UV irradiation, which generally caused oxidative damage. This result indicates that MpUGT737B1 and MpUGT741A1 may play a role in plant stress adaption. Subcellular localization indicates that MpUGT737B1 and MpUGT741A1 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.

Identification of a flavonoid C-glycosyltransferase from fern species Stenoloma chusanum and the application in synthesizing flavonoid C-glycosides in Escherichia coli

“…Confocal microscopy analysis demonstrated that the ScCGT1 protein is deposited in the nucleus and cytoplasm (Additional file 1: Fig. S8), which was consistent with the results from other plant glycosyltransferases [34,35].…”

“…The enzyme assay was performed with 200 mM Tris HCl (pH 7.5), 1 mM Dithiothreitol (DTT), 0.1 mM substrate (phloretin, apigenin, luteolin, 2-hydroxynaringenin, and 2-hydroxyeriodictyol), 1 mM sugar donor, and 10 μg of purified proteins (35 °C, 1 h) [34]. The reactions were terminated with methanol or HCl.…”

“…For transient expression analysis, the ScCGT1 correct construct was infiltrated into the bottom of N. benthamiana leaves. GFP signals were detected following the procedure reported previously [34].…”

Functional specialization of two UDP‐glycosyltransferases MpUGT735A2 and MpUGT743A1 in the liverworts Marchantia polymorpha

“…Several flavonoid‐GTs have been investigated in liverworts. In M. polymorpha , two bibenzyl UGTs were identified (Xiong et al, 2022). To broaden our understanding of UGTs responsible for flavonoids glycosylation in liverworts, we screened the M. polymorpha genomes and characterized two UGTs with different catalytic characteristics in the present investigation.…”

“…However, the in-depth investigation of the downstream modification genes, such as UGTs in M. polymorpha, is still insufficient. The M. polymorpha genome comprises 37 UGT genes and of these, only two UGTs (MpUG-T741A1 and MpUGT737B1) that have been functionally characterized, which exhibit high catalytic activity toward bibenzyls and proved to be involved in the antioxidant properties of M. polymorpha (Bowman et al, 2017;Xiong et al, 2022). This investigation aimed to uncover the functions of other UGTs to better elucidate the natural products in M. polymorpha.…”