Flavonoid biosynthesis in gerbera-hybrids: Enzymology and genetics

The biosynthetic pathway to anthocyanins, flavones and flavonols is well known. Chemogeneüc investigations of Gerbera flowers indicated two blocks at different steps of the pathway leading to acyanic flowers. One block most probably concerns flavanone 3-hydroxylase (FHT) and the other dihydroflavonol 4-reductase (DFR). The formation of flavones is assumed to be catalysed by flavone synthase II (FNS II). Chemogenetic investigations indicated that this step is controlled by a gene named Fns. Up to now, no mutant was found for regulation of the enzyme activity of flavonol synthase (FLS). The formation of cyanidin instead of pelargonidin depends on the activity of the enzyme flavonoid 3'-hydroxylase (F3'H). This hydroxylation reaction is assumed to be controlled by the gene named F3'h. Surprisingly, in some lines the formation of cyanidin was found to be suppressed by an as yet not identified dominant factor.