Metabolomic profiling of the astaxanthin accumulation process induced by high light in Haematococcus pluvialis

The growth of Haematococcus pluvialis exposed to high light was divided into three pigmentation phases: a green phase, a yellow phase and a red phase. Classification was based on astaxanthin and chlorophyll content and cell morphology. Metabolic profiling of the three pigmentation phases was performed. A total of 81 metabolites were identified and quantified by gas chromatography-mass spectrometry, including 23 amino acids, 19 sugars, 15 organic acids, 8 alcohols, 7 amines, 4 nucleic acids and 5 others. These were subdivided into four groups according to their changes during the three phases. The clustering of metabolites was revealed, and potential biomarkers were identified by principal component analysis, partial least squares analysis and hierarchical clustering analysis, suggesting details of the metabolic pathways of cells. The contents of some cytoprotective metabolites were increased in the yellow phase, such as sucrose, proline and glutamic acid. The precursors of these metabolites are the intermediates of the Calvin cycle and the TCA cycle, indicated those two cycles provided more precursors for the synthesis of the cytoprotective metabolites. A hypothetical metabolic regulation model of H. pluvialis exposed to high light was proposed. Our study provides the first metabolomics view of the astaxanthin accumulation process that is induced by high light in H. pluvialis.