The Arabidopsis UDP‐glycosyltransferases UGT79B2 and UGT79B3, contribute to cold, salt and drought stress tolerance via modulating anthocyanin accumulation

<jats:title>Summary</jats:title><jats:p>The plant family 1 UDP‐glycosyltransferases (UGTs) are the biggest GT family in plants, which are responsible for transferring sugar moieties onto a variety of small molecules, and control many metabolic processes; however, their physiological significance in planta is largely unknown. Here, we revealed that two Arabidopsis glycosyltransferase genes, <jats:italic>UGT79B2</jats:italic> and <jats:italic>UGT79B3</jats:italic>, could be strongly induced by various abiotic stresses, including cold, salt and drought stresses. Overexpression of <jats:italic>UGT79B2</jats:italic>/<jats:italic>B3</jats:italic> significantly enhanced plant tolerance to low temperatures as well as drought and salt stresses, whereas the <jats:italic>ugt79b2/b3</jats:italic> double mutants generated by RNAi (RNA interference) and CRISPR‐Cas9 strategies were more susceptible to adverse conditions. Interestingly, the expression of <jats:italic>UGT79B2</jats:italic> and <jats:italic>UGT79B3</jats:italic> is directly controlled by CBF1 (CRT/DRE‐binding factor 1, also named DREB1B) in response to low temperatures. Furthermore, we identified the enzyme activities of UGT79B2/B3 in adding UDP‐rhamnose to cyanidin and cyanidin 3‐O‐glucoside. Ectopic expression of <jats:italic>UGT79B2</jats:italic>/<jats:italic>B3</jats:italic> significantly increased the anthocyanin accumulation, and enhanced the antioxidant activity in coping with abiotic stresses, whereas the <jats:italic>ugt79b2/b3</jats:italic> double mutants showed reduced anthocyanin levels. When overexpressing <jats:italic>UGT79B2/B3</jats:italic> in <jats:italic>tt18</jats:italic> (<jats:italic>transparent testa 18</jats:italic>), a mutant that cannot synthesize anthocyanins, both genes fail to improve plant adaptation to stress. Taken together, we demonstrate that <jats:italic>UGT79B2</jats:italic> and <jats:italic>UGT79B3</jats:italic>, identified as anthocyanin rhamnosyltransferases, are regulated by CBF1 and confer abiotic stress tolerance via modulating anthocyanin accumulation.</jats:p>