ALGOMICS - Proteomic profiling of oil bodies isolated from the unicellular green microalga Chlamydomonas reinhardtii: with focus on proteins involved in lipid metabolism

Oil-bodies are sites of energy storage in many organisms including microalgae. As a first step toward understanding oil accumulation in algae, we took a proteomic approach on purified oil-body fraction from the model microalga Chlamydomonas reinhardtii grown under nitrogen deprivation. Among the 240 proteins (?2 peptides) identified by LC-MS/MS, 33 were putatively involved in metabolism of lipids (mostly acyl-lipids and sterols). Compared to a recently reported Chlamydomonas oil-body proteome, 19 additional proteins of lipid metabolism were identified, including a glycerol 3-phosphate acyltransferase (GPAT), a lysophosphatidic acid acyltransferase (LPAT) and a putative phospholipid:diacylglycerol acyltransferase (PDAT), spanning the key steps of the triacylglycerol synthesis pathway. In addition, proteins putatively involved in deacylation/reacylation, sterol synthesis, lipid signaling and lipid trafficking were found to be associated to the oil body fraction. This dataset thus provides evidence that in Chlamydomonas oil-bodies are not only storage compartments but also are dynamic structures likely to be involved in processes such as oil synthesis, degradation and lipid homeostasis. The proteins identified here should provide useful targets for genetic studies aiming at increasing our understanding of triacyglycerol synthesis and the role of oil-bodies in microalgal cell functions.