Nitrogen limitation and hydrogen peroxide act synergistically to enhance lipids accumulation via ROS/Ca2+ dependent mechanism in Chlorella sorokiniana

Abstract

The main aim of the present study is to assess the effects of combined nitrogen limitation and hydrogen peroxide (H2O2) treatment on lipid accumulation in Chlorella sorokiniana. Furthermore, to study the regulative networks involved in the lipid accumulation of microalgae, the relationships between reactive oxygen species (ROS), Ca2+ and four lipogenic genes (mitogen-activated protein kinase: MAPK; heteromeric acetyl-CoA carboxylase beta subunit: accD; b-ketoacyl-ACP synthase III: KASIII; diacylglycerol acyltransferase: DGAT) were also analyzed. The results indicated that the contents of chlorophyll a, carbohydrate and protein were decreased, while the lipid content and levels of endogenous ROS, Ca2+ were increased under nitrogen limitation groups with H2O2 added. Further research indicated that the increased ROS level could affect lipid accumulation through lipogenic genes expression. In addition, the interplays of ROS and Ca2+ may be found. This study provides an effective strategy to improve the lipid accumulation in C. sorokiniana, and offers evidence of ROS, Ca2+ and lipogenic genes in the accommodation of lipid biosynthesis in microalgae under combined treatment of nitrogen limitation and H2O2.