Identification of gene transcripts involved in lipid biosynthesis in Chlamydomonas reinhardtii under nitrogen, iron and sulfur deprivation.

Chlamydomonas reinhardtii is able to accumulate large amounts of triacylglycerides, the major feedstock for biodiesel production, when grown under stress conditions. In order to characterize gene transcripts induced under nitrogen, iron, and sulfur deprivation in C. reinhardtii; 583 expressed sequence tags (ESTs) were generated through a cDNA library. These sequences were subjected to contig assembly resulting in 30 contigs and 76 singletons. The comparison of the ESTs obtained with public databases allowed to assign putative functions to 66.7 % of the sequences. An important group of the identified genes are related to the lipid metabolic process. A phylogenetic analysis of these sequences identified five isoforms of diacylglycerol O-acyltransferase type 2 (DGAT-2). These genes were selected to measure their relative expression under these stress conditions by means of qRT-PCR. According to the results, the accumulation of DGTT1 mRNA increases considerably under nitrogen and iron inanition when compared to the other isoforms, which indicated that each isoform participates at different levels under each stress condition. These results can help to identify potential genes to be overexpressed by genetic engineering in C. reinhardtii.