Time-resolved transcriptome analysis under sulfur starvation stress in the green microalga Chromochloris zofingiensis

Chromochloris zofingiensis has been proposed as a potential producer of lipids and the high-value carotenoid astaxanthin. Previous studies have demonstrated that TAG (triacylglycerol) and astaxanthin accumulated in a well-coordinated manner in response to different stresses in C. zofingiensis. The integrated production of lipids with co-products emerges as a new research direction and is proposed to be a promising approach toward offsetting the algal biodiesel production cost. Therefore, it is suggested C. zofingiensis can serve as research models for the integrated production. Sulfur starvation stress simultaneously induced TAG and astaxanthin accumulation in C. zofingiensis. To understand the mechanism underlying TAG and astaxanthin accumulation induced by sulfur starvation stress, we applied time-resolved high-throughput mRNA sequencing in C. zofingiensis. Overall design: Chromochloris zofingiensis cells in exponential phase were harvested by centrifugation at 5000 rpm for 5 min and washed twice. Then cells (initial cell density at 0.5 g/L) were re-inoculated in modified Kuhl medium in which MgSO4 was replaced with MgCl2 for sulfur starvation stress. Cells were collected for RNA isolation at 0 h and 6, 12, 24, 48 h after re-inoculation. After 48 h of sulfur starvation, cells were re-inoculation into fresh kuhl medium for sulfur replenishment and samples were collected after 12 h. Three biological replicates of algal cultures were carried out. In total, 18 samples were collected for mRNA-seq.