Transcriptome analysis for phosphorus starvation-induced lipid accumulation in Scenedesmus sp.

Phosphorus stress was applied to enhance the lipid production in Scenedesmus sp. The highest lipid production (350 mg L⁻¹) and lipid content (approximately 41.0% of dry weight) were obtained by addition of 2 mg L⁻¹ NaH₂PO₄·2H₂O every 2 days, which were higher than those in replete phosphorus. Correspondingly, carbohydrate content decreased significantly. We speculated that phosphorus limitation could block starch biosynthesis, and photosynthate flow tended to fatty acid biosynthesis to cope with stress. To investigate the mechanism that phosphorus stress triggers the carbon fixation to lipid biosynthesis, the transcriptome analysis was carried out by the Illumina RNA-seq platform. A total of 2897 genes were identified as differentially expressed genes. The observed overexpression of lipid production under phosphorus stress was bolstered by up-regulation of genes encoding for DGAT and pyruvate kinase, activation of carbohydrate metabolism pathway and fatty acid biosynthesis, and repression of carbohydrate synthesis-presumably to shunt the carbon flux toward TAG biosynthesis. The transcriptome will be useful to understand the lipid metabolism pathway and obtain the engineering economic algae species aimed at biodiesel production. [ABSTRACT FROM AUTHOR]