Characteristics of lipid biosynthesis in Chlorella pyrenoidosa as subjected to nutrient deficiency stress

Abstract

ABSTRACT In this work, changes in intracellular compositions and gene expression levels of Chlorella pyrenoidosa were investigated under N-, P- and S-deficient stress conditions. The lipid content of C. pyrenoidosa in N-free culture at the end of the experiment was 43.30 ± 2.95%, representing an increase by 103.2% compared with that in the full medium (21.31 ± 3.27%). Moreover, a high cellular reactive oxygen species (ROS) level and a decreasing chlorophyll content were observed under the three stress conditions. The expression levels of the genes related to glycolysis, carbon assimilation and CO2 fixation decreased in the stress modes, while the expression levels of the genes related to lipid synthesis increased. As a result, an enhancement of lipid biosynthesis under the nutrient-deficiency stress condition was achieved, and the intracellular lipid content of C. pyrenoidosa was obviously increased. The result indicates that the ROS signal pathway may mediate the metabolic pathways involved in CO2 fixation, glycolysis, carbon assimilation and lipid synthesis in nutrient-deficiency stress mode.