Identification of flavonoid 3′-hydroxylase in the yellow flower of Delphinium zalil

The flowers of delphinium cultivars owe their coloration to anthocyanins such as delphinidin or pelargonidin derivatives. To date, no delphinium cultivars have been found with red flowers due to the presence of cyanidin derivatives. This suggests that delphiniums do not have cyanidin biosynthesis ability because of the loss of function of flavonoid 3′ hydroxylase (F3′H). Here, we show that the wild delphinium species Delphinium zalil (synonym semibarbatum) can accumulate quercetin 3-glucosides in its sepals, presumably through F3′H activity. We isolated F3′H cDNA from D. zalil (DzF3′H) and produced a recombinant enzyme from a yeast transformant. The recombinant DzF3′H protein could convert naringenin, apigenin, dihydrokaempferol and kaempferol to eriodictyol, luteolin, dihydroquercetin and quercetin, respectively. An expression analysis confirmed that blue flowered D. grandiflorum does not express F3′H, and also showed that flavonoid 3′,5′-hydroxylase and anthocyanidin synthase do not function in D. zalil sepals. DzF3′H can act as a flavonoid hydroxylase to produce cyanidin accumulation. The introduction of the DzF3′H gene into other delphinium species by conventional breeding may enable development of cultivars with novel flower colors.