Characterization of the Flavonol Synthase Gene Family Reveals Bifunctional Flavonol Synthases.

Flavonol synthase (FLS) is a key enzyme for the formation of flavonols, which are a subclass of the flavonoids. FLS catalyzes the conversion of dihydroflavonols to flavonols. The enzyme belongs to the 2-oxoglutarate-dependent dioxygenases (2-ODD) superfamily. We characterized the gene family of that covers 13 genes, based on the genome sequence of the cultivar Express 617. The goal was to unravel which genes are relevant for seed flavonol accumulation in the amphidiploid species . Two homeologs were identified and shown to encode bifunctional enzymes. Both exhibit FLS activity as well as flavanone 3-hydroxylase (F3H) activity, which was demonstrated and . and are capable of converting flavanones into dihydroflavonols and further into flavonols. Analysis of spatio-temporal transcription patterns revealed similar expression profiles of genes. Both are mainly expressed in reproductive organs and co-expressed with the genes encoding early steps of flavonoid biosynthesis. Our results provide novel insights into flavonol biosynthesis in and contribute information for breeding targets with the aim to modify the flavonol content in rapeseed.