K. Obsuwan, D.A. Hieber, R.G. Mudalige-Jayawickrama, A.R. Kuehnle
Anthocyanidins are water-soluble pigments that accumulate in the vacuole and can be responsible for red-pink cyanidin, orange pelargonidin, and blue delphinidin in flowers. Production of the three primary classes of anthocyanidins by the phenyl propanoid pathway is controlled by the availability of the colorless substrates dihydrokaempferol (DHK), dihydroquercetin (DHQ), and dihydromyricetin (DHM) and the activities of flavonoid 3'-hydroxylase (F3'H), flavonoid 3',5'-hydroxylase (F3'5'H), and Dihydroflavonol 4-reductase (DFR). Conversion of those three dihydroflavonoids into leucoanthocyanidins is a required step in anthocyanin biosynthesis and is catalyzed by DFR. Substrate specificity of DFR explains the absence of certain colors among some ornamental plants, which make this enzyme an important target for flower color manipulation through genetic engineering. In order to characterize DFR in two major subtropical orchids, full-length cDNA clones encoding DFR were isolated from petals of Dendrobium × Icy Pink ‘Sakura’ and Oncidium × Gower Ramsey using a RT-PCR based technique. The substrate specificity of Dendrobium dfr and Oncidium dfr was investigated by genetic transformation of the mutant Petunia line W80 that predominantly accumulating DHK. Chemical analysis of transformed lines revealed that both Dendrobium dfr and Oncidium dfr can efficiently catalyze the reduction of DHK, DHQ and DHM resulting in the production of pelargonidin, cyanidin and delphinidin with no substrate specificity.
Obsuwan, K., Hieber, D.A., Mudalige-Jayawickrama, R.G. and Kuehnle, A.R. (2007). FUNCTIONAL CHARACTERIZATION OF DENDROBIUM AND ONCIDIUM DFR IN PETUNIA HYBRIDA MODEL. Acta Hortic. 764, 137-144
DOI: 10.17660/ActaHortic.2007.764.16
DFR, Oncidium, Dendrobium, orchids, DHK, Pelargonidin

Acta Horticulturae