Understanding fatty acid composition and lipid profile of rapeseed oil in response to nitrogen management strategies

The fatty acid composition of rapeseed seeds plays an important role in oil quality for human nutrition and a healthy diet. A deeper understanding of fatty acid composition and lipid profiles in response to different nitrogen managements is critical for producing healthier rapeseed oil for the human diet. The fatty acid composition and lipid profiles were characterized through targeted GC-MS and lipidomics analysis (UPLC-MS) in this study. The results showed that nitrogen management significantly altered the fatty acid composition, thereby influencing oil quality when it is used to maximize the seed yield of rapeseed. Several fatty acid components (particularly oleic acid, linoleic acid, and linolenic acid) decreased significantly with increasing N application rate. A total of 1212 differential lipids in response to different N levels in the two varieties were clearly identified, that can be categorized into five classes, including 815 glycerolipids (GLs), 195 glycerophospholipids (GPs), 155 sphingo-lipids (SPs), 32 sterols (STs), and 15 fatty acyls (FAs). These differential lipids are likely to participate in lipid metabolism and signal transduction. Co-expression lipid modules were determined, and the key lipids, such as triglyceride (20:0/16:0/16:0; 18:0/18:1/18:3; 8:0/11:3/18:1), were found to be strongly related to several predominant fatty acids such as oleic acid and linoleic acid. The results further imply that some identified lipids are involved with lipid metabolism and could affect the fatty acid composition, which provide a theoretical guidance for increasing seed oil in Brassica napus.