AUTHOR=Schilbert Hanna Marie , Schöne Maximilian , Baier Thomas , Busche Mareike , Viehöver Prisca , Weisshaar Bernd , Holtgräwe Daniela 

TITLE=Characterization of the Brassica napus Flavonol Synthase Gene Family Reveals Bifunctional Flavonol Synthases

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.733762

DOI=10.3389/fpls.2021.733762

ISSN=1664-462X

ABSTRACT=<p>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 <italic>FLS</italic> gene family of <italic>Brassica napus</italic> that covers 13 genes, based on the genome sequence of the <italic>B. napus</italic> cultivar Express 617. The goal was to unravel which <italic>BnaFLS</italic> genes are relevant for seed flavonol accumulation in the amphidiploid species <italic>B. napus</italic>. Two <italic>BnaFLS1</italic> homeologs were identified and shown to encode bifunctional enzymes. Both exhibit FLS activity as well as flavanone 3-hydroxylase (F3H) activity, which was demonstrated <italic>in vivo</italic> and <italic>in planta</italic>. <italic>BnaFLS1-1</italic> and <italic>-2</italic> are capable of converting flavanones into dihydroflavonols and further into flavonols. Analysis of spatio-temporal transcription patterns revealed similar expression profiles of <italic>BnaFLS1</italic> 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 <italic>B. napus</italic> and contribute information for breeding targets with the aim to modify the flavonol content in rapeseed.</p>