Response of lipid biosynthesis in Chlorella pyrenoidosa to intracellular reactive oxygen species level under stress conditions

An increase in the total lipid content in algal cells under stress conditions is often accompanied by an increase in reactive oxygen species (ROS). However, the link between these two events is unclear. In this study, the regulatory mechanism of ROS formation on lipid accumulation in C. pyrenoidosa was investigated using a Fenton-like reaction. A high Spearman correlation coefficient of 0.901 was obtained between the Hydroxyl radical (OH center dot) level and lipid content. Importantly, the increase in the total lipid content was clearly coupled with a significant increase in the intracellular OH center dot concentration rather than increases in the H2O2 and O-2(center dot-) concentrations. Transcriptome data confirms that most of the differential expression genes (DEGs) involved in fatty acid and glycerolipid biosynthesis were up-regulated by the increased OH center dot under stress conditions. These results reveal that lipid accumulation in algal cells was promoted by OH center dot.