Date of this Version
Published in Algal Research 10 (2015), pp 110–120. doi 10.1016/j.algal.2015.04.019
Triglyceride (TAG) synthesis during nitrogen starvation and recovery was addressed using Coccomyxa subellipsoidea by analyzing acylchain composition and redistribution using a bioreactor-controlled time course. Galactolipids, phospholipids and TAGs were profiled using liquid chromatography tandem mass spectroscopy (LC–MS/MS). TAG levels increased linearly through 10 days of N starvation to a final concentration of 12.6% dry weight (DW), while chloroplast membrane lipids decreased from 5% to 1.5% DW. The relative quantities of TAG molecular species, differing in acyl chain length and glycerol backbone position, remained unchanged from 3 to 10 days of N starvation. Six TAG species comprised approximately half the TAG pool. An average of 16.5% of the acyl chains had two or more double bonds consistent with their specific transfer from membrane lipids to TAGs during N starvation. The addition of nitrate following 10 days of N starvation resulted in a dramatic shift from chloroplast-derived to endoplasmic reticulum-derived galactolipids (from <12% to >40%). A model for TAG synthesis in C. subellipsoidea was developed based on the acquired data and known plant pathways and data presented.