Intervention of triethylamine on Dunaliella tertiolecta reveals metabolic insights into triacylglycerol accumulation

Dunaliella tertiolecta is a highly oil-producing microalgae. Here, we report its de novo transcriptome assembly and quantitative gene expression analysis of the intervention of triethylamine, with a focus on the complex interactions of pathways involved in the production of triacylglycerol (TAG) biofuel precursors. After growing under 100 ppm triethylamine, we quantified the cellular content of the major biomolecules, including total lipids, single cell oil content, and lipid components. The transcriptome was assembled de novo and the main functional classes, related pathways, and expression of important genes were quantified by the mapping of reads to the transcriptome. Almost 65,925 high-quality readings were produced on the Illumina HiSeq sequencing platform. In addition to the observed overexpression of the fatty acid synthesis pathway, TAG production during triethylamine was not through the Kennedy pathway, but the bypass pathway by high expression of phosphate: diacylglycerol acyltransferase. The glycolytic pathway has also been down-regulated, not only in the cytoplasm but also in the chloroplast. Triosephosphate translocator was downregulated, and the DNA binding with One Finger protein gene was upregulated. The quantitative transcriptome study reveals a broad overview of how triethylamine stress leads to excessive TAG production in Dunaliella, and provides various genetic engineering goals and strategies to improve biofuel precursors in oleaginous microalgae.