Lipid content in Scenedesmus species correlates with multiple genes of fatty acid and triacylglycerol biosynthetic pathways

The feasibility of microalgae based biodiesel depends upon the selection of strains having high lipid content without compromising growth. The molecular basis governing storage lipid biosynthesis is poorly understood in microalgae including Scenedesmus, which has been identified as a potential oil-producing microalga. Eighteen genes of fatty acid and triacylglycerol biosynthesis were identified in Scenedesmus dimorphus through comparative genomics and transcriptome mining and their expression was examined in three growth stages viz., exponential, early stationary, late stationary phase and two stress conditions induced by nitrogen deficiency and high salinity among two lipid contrasting strains of S. dimorphus, SD12 (26%), SD16 (5%) and one strain of Scenedesmus quadricauda SQ19 (14%). Most of the genes showed relatively higher expression in high lipid strain, SD12 with up to 50 folds and 25 folds increase in transcript abundance of 9 genes compared to SD16 and SQ19, respectively. Eleven genes showed upregulation at late stationary phase and under stress conditions, suggesting role of multiple genes in controlling lipid content. Comparison of gene expression across differential conditions among three contrasting strains unveiled six key genes, ACP, FATA, KASII, LPAAT, PAP and DGAT that can be chosen as potential targets for designing a genetic intervention strategy for further enrichment of lipid profile in Scenedesmus species.