As concerns about energy security and climate change have increased, microalgae have emerged as a promising feedstock for biofuel production. Microalgal oils have also recently gained popularity as nutraceutical supplements, such as serving as a source of omega-3 fatty acids. If microalgal oil content is to be tailored to a favorable composition for biofuel or nutritional purposes, the major biochemical pathways contributing to oil synthesis must be characterized. Chlamydomonas reinhardtii was chosen as a model microalga for this work because it has served as a model system for several areas of biology for well over fifty years, and thus has many resources and tools available for its study. Several environmental stresses are known to induce oil accumulation in microalgae, and deprivation of nitrogen was chosen in this study as it is the most widely-used, is easily applied, and induces very strong accumulation of neutral oil. This dissertation describes my research findings on the biochemical relationship between membrane glycerolipids and triacylglycerol (TAG) in C. reinhardtii during nitrogen deprivation and resupply. It includes the results of my work to elucidate the flow of fatty acids during TAG synthesis and the fate of fatty acids during TAG breakdown. It also includes my analysis of the biochemical mechanisms by which membrane glycerolipids are converted into TAG as well as which lipid moieties are converted into TAG. Time course experiments and isotopic labeling were the methods used in these analyses to trace the flow of carbon between biomolecules. An overview of acyl editing is also provided in this dissertation, as it is an important component of the TAG synthesis pathway in plants that is under-explored in microalgae. Finally, the dissertation concludes with future directions and experiments that would help address the outstanding questions that remain in C. reinhardtii lipid biochemistry.
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