New glycosyltransferase RpUGT2 from Rheum palmatum involved in the flavonoid glycoside biosynthesis

Uridine diphosphate-dependent glycosyltransferases (UGTs) serve as key mediators in the glycosylation of plant metabolites, thereby inducing alterations in their physicochemical properties and bioactivities. Particularly, flavonoid glycosides are synthesized from aglycones through reactions catalyzed by typical UGTs. In our present investigation, we successfully cloned a novel UGT, RpUGT2, originating from Rheum palmatum, a highly regarded traditional Chinese herb known for its abundant genetic diversity. Sequence alignment and phylogenetic analysis indicated the close phylogenetic proximity of RpUGT2 to Vitis vinifera. The recombinant RpUGT2 protein, produced heterologously in Escherichia coli, displayed robust catalytic activity towards a spectrum of flavonoids. Mutational analyses revealed that specific amino acid sequence modifications could result in the loss of enzymatic activity in RpUGT2. This study has thus provided potential candidate genes, RpUGT2, for prospective applications in the metabolic engineering of flavonoid compounds in plants.