Genetic control of flavone synthase II activity in flowers of Gerbera hybrids

In flower extracts of defined genotypes of Gerbera hybrids an enzyme activity was demonstrated which catalyses the introduction of a double bound between the C atoms 2 and 3 of the flavanones naringenin and eriodictyol. The products formed were the corresponding flavones, apigenin and luteolin. Similar to flavone synthases II from other plant species, the enzyme activity of this cytochrome P450-dependent monooxygenase was found to be localized in the microsomal fraction. The reaction required NADPH as cofactor and had a pH-optimum of about 7.5. Flavone synthase II activity was detectable only in flower extracts of genotypes with dominant wild-type alleles at the locus Fns, but not in lines with recessive alleles (fns fns). The results establish for the first time a correlation between a gene and the enzyme activity of flavone synthase II.