Lipid accumulation during nitrogen and sulfur starvation in Chlamydomonas reinhardtii overexpressing a transcription factor

Algal triacylglycerol biosynthesis is of increasing interest for potential biodiesel production. In this study, we investigated the lipids content and gene expression changes in Chlamydomonas reinhardtii strain overexpressing a Dof-type transcription factor in response to nutrient deficiency. The untransformed strain grew in TAP complete medium and accumulated only 4.1%25 dry cell weight of fatty acids; while in the transgenic strain, the total fatty acids content increased to 15.58 and 17.02%25 in medium without sulfur or nitrogen, respectively. The major fatty acids found in the stressed microalgae were palmitic, oleic (all strains), and linoleic (transgenic strain). Additionally, we observed that the transgenic strain does not have a defect in carbon partitioning but redirect the carbon flux from starch to lipids. Among the most interesting results in the transcriptional profile, we found an overexpression of the enzymes lecithin cholesterol acyltransferase, glycerol-3-phosphatase acyltransferase, and phosphatidylcholine-sterol O-aciltransferase. As observed in this study, the combination of strategies (overexpression of a transcription factor and nutrient deficit) increases not only the content of total lipids in transgenic cells compared to an untransformed strain but, also the proportion of specific fatty acids that are desirable for biodiesel production. © 2018, Springer Science%2bBusiness Media B.V., part of Springer Nature.

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