Background: Flavonoids are a kind of important secondary metabolite and are commonly considered to provide protection to plants against stress and UV-B for a long time. Anthocyanidin synthase (ANS), which encodes a dioxygenase in the flavonoid pathway, catalyzes the conversion of leucoanthocyanidins to anthocyanidins, but there is no direct evidence indicating that it provides tolerance to stress in plants.

Results: To investigate whether ANS can increase tolerance to abiotic stress, MaANS was isolated from mulberry fruits and transformed into tobacco. Our results suggested that the bacterially expressed MaANS protein can convert dihydroquercetin to quercetin. Overexpression of MaANS remarkably increased the accumulation of total flavonoids in transgenic lines and anthocyanins in corollas of flowers. Transgenic lines showed higher tolerance to NaCl and mannitol stress.

Conclusions: These results indicated that MaANS participates in various dioxygenase activities, and it can protect plants against abiotic stress by improving the ROS-scavenging ability. Thus, this alternative approach in crop breeding can be considered in the improvement of stress tolerance by enriching flavonoid production in plants.