Silencing of BnTT1 genes altered the seed color, seed size and seed weight in B. napus. Transgenic seeds showed down-regulated expression of genes involved in flavonoid biosynthesis. Silencing of BnTT1 genes decreased flavonols and proanthocyanidins in B. napus. Repression of BnTT1 genes altered the expression of genes involved in fatty acid biosynthesis. Repression of BnTT1 genes altered the seed fatty acid composition.