Glycerolipid remodeling triggered by phosphorous starvation and recovery in Nannochloropsis oceanica

To understand the function of DGTS (diacylglyceryl-N,N,N-trimethyl-homoserine) as substitution of PC (phosphatidylcholine), Nannochloropsis oceanica has been chosen as the model system because it has DGTS and PC simultaneously. Phosphorus is a regulator for DGTS and PC. Generally, DGTS increases and correspondingly PC decreases under phosphorous starvation. However, the function of DGTS and its fatty acid origin under phosphorous starvation, and the resurgence of PC triggered by phosphorus recovery remain not clarified completely. In the present study, we investigated the effect of phosphorus starvation and recovery on polar glycerolipid remodeling in N. oceanica based on quantitative lipidomic data. Through targeted lipidomics analysis, we proposed that, under phosphorus deprivation, DGTS serves as the central intermediate in glycerolipid remodeling via acting as the carrier of the C18 fatty acids desaturation by replacement of PC, maintaining the biosynthesis of EPA (eicosapentaenoic acid) and providing the EPA acyl as a precursor for formation of chloroplast glycolipids. The prokaryotic molecular species of DGTS are mainly from de novo biosynthesis pathway and make the major contribution for the DGTS increase. In the process of resupplying phosphorus, PC increased attributing to hydrolysis of TAG, generating diacylglycerol for PC biosynthesis. These new information demonstrated that DGTS and PC varied conversely in different metabolic pathways as revealed by targeted lipidomic data.