Flavonol synthase (FLS) is a key enzyme for the formation of flavonols, which are a subclass of the flavonoids. FLS catalyses the conversion of dihydroflavonols to flavonols. The enzyme belongs to the 2-oxoglutarate-dependent dioxygenases (2-ODD) superfamily. We characterized the FLS gene family of Brassica napus that covers 13 genes, based on the genome sequence of the B. napus cultivar Express 617. The goal was to unravel which BnaFLS genes are relevant for seed flavonol accumulation in the amphidiploid species B. napus. Two BnaFLS1 homeologs were identified and shown to encode bifunctional enzymes. Both exhibit FLS activity as well as flavanone 3-hydroxylase (F3H) activity, which was demonstrated in vivo and in planta. BnaFLS1-1 and -2 are capable of converting flavanones into dihydroflavonols and further into flavonols. Analysis of spatio-temporal transcription patterns revealed similar expression profiles of BnaFLS1 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 B. napus and contribute information for breeding targets with the aim to modify the flavonol content in rapeseed.

中文翻译：

---

欧洲油菜黄酮醇合酶基因家族的表征揭示了双功能黄酮醇合酶

黄酮醇合成酶 (FLS) 是形成黄酮醇的关键酶，黄酮醇是类黄酮的一个亚类。FLS 催化二氢黄酮醇向黄酮醇的转化。该酶属于 2-酮戊二酸依赖性双加氧酶 (2-ODD) 超家族。我们基于欧洲油菜栽培品种 Express 617的基因组序列对涵盖 13 个基因的欧洲油菜FLS基因家族进行了表征。目标是阐明哪些BnaFLS基因与双二倍体物种欧洲油菜中种子黄酮醇的积累有关。两个BnaFLS1同源物被鉴定并显示编码双功能酶。两者都表现出 FLS 活性以及黄烷酮 3-羟化酶 (F3H) 活性，这在体内和植物中得到证实。BnaFLS1-1和-2能够将黄烷酮转化为二氢黄酮醇并进一步转化为黄酮醇。时空转录模式的分析揭示了BnaFLS1基因的相似表达谱。两者都主要在生殖器官中表达，并与编码黄酮类生物合成早期步骤的基因共表达。我们的研究结果提供了对欧洲油菜中黄酮醇生物合成的新见解，并为育种目标提供信息，旨在改变油菜籽中的黄酮醇含量。