RT Journal Article
SR Electronic
T1 UDP-glucose:anthocyanidin 3-<em>O</em>-glucoside-2”-<em>O</em>-glucosyltransferase catalyzes further glycosylation of anthocyanins in purple <em>Ipomoea batatas</em>
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 332486
DO 10.1101/332486
A1 Hongxia Wang
A1 Chengyuan Wang
A1 Weijuan Fan
A1 Jun Yang
A1 Ingo Appelhagen
A1 Yinliang Wu
A1 Peng Zhang
YR 2018
UL http://biorxiv.org/content/early/2018/05/28/332486.abstract
AB Glycosylation contributes to the diversity and stability of anthocyanins in plants. The process is catalyzed by various glucosyltransferases using different anthocyanidin aglycones and glycosyl donors. An anthocyanidin 3-O-glucoside-2”-O-glucosyltransferase (3GGT) from purple sweetpotato (cv. Ayamurasaki) served for the catalytic conversion of anthocyanidin 3-O-glucoside into anthocyanidin 3-O-sophoroside, which is functionally different from the 3GGT ortholog of Arabidopsis. The phylogenetic analysis indicates regioselectivity of 3GGT using UDP-xylose or UDP-glucose as the glycosyl is divergent between Convolvulaceae and Arabidopsis. Homology-based protein modeling and site-directed mutagenesis of Ib3GGT and At3GGT suggested that the Thr-138 of Ib3GGT is a key amino acid residue for UDP-glucose recognition and plays a major role in sugar donor selectivity. The wild type and ugt79b1 mutants of Arabidopsis plants overexpressing Ib3GGT produced the new component cyanidin 3-O-sophoroside. Moreover, Ib3GGT expression was associated with anthocyanin accumulation in different tissues during Ayamurasaki plant development and was regulated by the transcription factor IbMYB1. The localization assay of Ib3GGT showed that further glycosylation occurs in the cytosol and not endoplasmic reticulum. The present study revealed the function of Ib3GGT in further glycosylation of anthocyanins and its Thr-138 is the key amino acid residue for UDP-glucose recognition.