Arabidopsis UDP-glycosyltransferase 78D1-overexpressing plants accumulate higher levels of kaempferol 3-O-β-D-glucopyranoside than wild-type plants

Flavonols are a class of flavonoids that are found in most plants. Certain flavonols exhibit anticancer, antioxidant, and antimicrobial functions. An array of genes plays a role in the regulation of flavonoid biosynthetic pathways, including the MYB-bHLH (basic helix-loop-helix-WD40 transcription factor complex. Flavonoids often display altered bioactivities after being glycosylated by the action of glycosyltransferases. These enzymes catalyze the transfer of sugars from a donor to various acceptors. In this study, we generated several transgenic lines of Arabidopsis that overexpress UDP-glycosyltransferase 78D1 (UGT78D1), which are hereafter referred to as UGT78D1-OX, to address three questions: (1) Can UGT78D1-OX seedlings accumulate more flavonols? (2) Can UGT78D1-OX seedlings accumulate more flavonols in the presence of sucrose? and (3) Will UGT78D1-OX be more sensitive to abiotic stresses? We observed that UGT78D1-OX seedlings accumulated specific types of kaempferol, while they had a decreased content of flavonols in the presence of sucrose. Contrary to our expectation, more anthocyanins accumulated in the UGT78D1-OX lines, although the expression of production of anthocyanin pigment 1 was slightly reduced in UGT78D1-OX seedlings compared with that in wildtype seedlings. It appeared that the overexpression of UGT78D1 did not interfere with abiotic stress tolerance in the mutant plants.