Certain eukaryotes can synthesize triacylglycerol using an acyl-CoA-independent pathway. This activity is mediated by phospholipid diacylglycerol acyl transferases that use fatty acids from phospholipids as acyl donors. In this perspective, we review the current knowledge on these enzymes and propose that local modulation of phospholipids mediated by this pathway impacts the function and morphology of the targeted organelle.

Triglycerides constitute an inert storage form for fatty acids deposited in lipid droplets and are mobilized to provide metabolic energy or membrane building blocks. The biosynthesis of triglycerides is highly conserved within eukaryotes and normally involves the sequential esterification of activated fatty acids with a glycerol backbone. Some eukaryotes, however, can also use cellular membrane lipids as direct fatty acid donors for triglyceride synthesis. The biological significance of a pathway that generates triglycerides at the expense of organelle membranes has remained elusive. Here we review current knowledge on how cells use membrane lipids as fatty acid donors for triglyceride synthesis and discuss the hypothesis that a primary function of this pathway is to regulate membrane lipid remodeling and organelle function.