Flavonoid biosynthesis in pink-flowered cultivars derived from 'William Sim' carnation (Dianthus caryophyllus)

Analyses for anthocyanin concentration and flavonoid composition of flowers of two white, four light-pink, four deep-pink, and three red cultivars derived from 'William Sim' carnation revealed that anthocyanin content increased from the light-pink-flowered cultivars, to the deep-pink-flowered cultivars, and to the red-flowered cultivars. Simultaneously, examination of gene expression of enzymes involved in anthocyanin biosynthesis showed that transcriptional levels of dihydroflavonol 4-reductase gene (DFR) and anthocyanidin synthase gene (ANS) in the deep-pink- flowered cultivars were correspondingly lower in the red-flowered cultivars, whereas those ofANS was much lower in the light-pink-flowered cultivars except in 'Lolyta'. In light-pink-flowered cultivars, transcripts of flavanone 3-hydroxylase gene (F3H) in 'Lolyta' and ANS in 'Dusty' were undetectable on the Northern blots, but both transcripts were detected on reverse transcription-polymerase chain reaction (RT-PCR). Low anthocyanin accumulation in pink-flowered cultivars seems to be regulated at different steps in anthocyanin biosynthesis.