Comparative Analysis of the Metabolic Profiles of Yellow- versus Black-Seeded Rapeseed Using UPLC–HESI–MS/MS and Transcriptome Analysis

The high levels of secondary metabolites in rapeseed play important roles in determining the oil quality and feeding value. Here, we characterized the metabolic profiles in seeds of various yellow- and black-seeded rapeseed accessions. Two hundred and forty-eight features were characterized, including 31 phenolic acids, 54 flavonoids, 24 glucosinolates, 65 lipid compounds, and 74 other polar compounds. The most abundant phenolic acids and various flavonoids (epicatechin, isorhamnetin, kaempferol, quercetin, and their derivatives) were widely detected and showed significant differences in distribution between the yellow- and black-seeded rapeseed. Furthermore, the related genes (e.g., BnTT3, BnTT18, BnTT10, BnTT12, and BnBAN) involved in the proanthocyanidin pathway had lower expression levels in yellow-seeded rapeseed, strongly suggesting that the seed coat color could be mainly determined by the levels of epicatechin and their derivatives. These results improve our understanding of the primary constituents of rapeseed and lay the foundation for breeding novel varieties with a high nutritional value.