Flower-specific expression of the Phalaenopsis flavonoid 3′, 5′-hydoxylase modifies flower color pigmentation in Petunia and Lilium

Abstract

Flavonoid 3′, 5′-hydoxylase (F3′5′H) is a key enzyme for biosynthesis of the blue anthocyanin pigment delphinidin. A number of F3′5′H genes from dicots have been tested for their effects on flower pigmentation; here F3′5′H from a monocot was tested for its effect on delphinidin accumulation in petals. To this end, F3′5′H (PhF3′5′H) from the orchid Phalaenopsis was expressed under the control of the chalcone synthase promoter in petunia flowers. Quantitative RT-PCR showed that PhF3′5′H was expressed mainly in the petal limb; this expression produced an increase in dihydromyricetin and delphinidin and a change in petal color from pink to deeper pink. To increase the accumulation of delphinidin, Hyacinth HyDFR, which encodes dihydroflavonol 4-reductase, and petunia DifF, which encodes a cytochrome b 5 that is required for full activity of F3′5′H were overexpressed. The HyDFR petunia transformants had a deeper color petal limb, increased dihydromyricetin and delphinidin contents and adaxial petals with a number of blue cells. The flowers of the DifF petunia transformants also showed a slight color change. We also tested PhF3′5′H in Lilium oriental ‘Sorbonne’, where transient PhF3′5′H expression by particle bombardment resulted in purple cells in the petals. Production of blue flowers by Phalaenopsis F3′5′H and hyacinth DFR potentially enables manipulation of flower color in ornamental plants, including production of blue flowers.