Expression of chimeric P450 genes encoding flavonoid-3 ',5 '-hydroxylase in transgenic tobacco and petunia plants

Flavonoid-3',5'-hydroxylase (F3'5'H), a member of the cytochrome P450 famil y, is the key enzyme in the synthesis of 3',5'-hydroxylated anthocyanins, w hich are generally required for blue or purple flowers. A full-length cDNA, TG1, was isolated from prairie gentian by heterologous hybridization with a petunia cDNA, AK14, which encodes F3'5'H, To investigate the in vivo func tion of TG1 and AK14, they were subcloned into a plant expression vector an d expressed under the control of the CaMV35S promoter in transgenic tobacco or petunia, both of which originally lack the enzyme, Transgenic petunia p lants had a dramatic change in flower color from pink to magenta with a hig h content of 3',5'-hydroxylated anthocyanins. In contrast, transgenic tobac co plants had minimal color change with at most 35% 3',5'-hydroxylated anth ocyanin content. These results indicate that the products of TG1 and AK14 h ave F3'5'H activity in planta and that interspecific gene transfer alters a nthocyanin pigment synthesis. The difference in apparent F3'5'H activity be tween tobacco and petunia is discussed. (C) 1999 Federation of European Bio chemical Societies.