Lipidomic profiling and discovery of lipid biomarkers in snow alga Chlamydomonas nivalis under salt stress

The snow alga Chlamydomonas nivalis is a typical microalgal species that can adapt and resist to natural habitats in the polar region and similar extreme environments. In response to various stress conditions, the change of lipid profile in cell membrane systems is known to play a vital role in cell survival and reproduction. In the present work, to elucidate the involvement of intracellular lipids in the molecular mechanism of cell response and adaptation to salt stress, C. nivalis was cultured and treated with different sodium chloride (NaCl) concentrations in different time courses. The ultra performance liquid chromatography/quadrupole-TOF-MS (UPLC/Q-TOF-MS)-based approach was developed for lipidomic profiling followed by multivariate statistical analysis including partial least squares discriminant analysis and orthogonal projection on latent structure discriminant analysis for data classification and potential biomarkers selection. Seven types and 35 kinds of polar lipid molecules were selected and identified as biomarkers, including monogalactosyldiacylglycerol, digalactosyldiacylglycerol, l, 2-diacylglyceryl-3-O-4'-(N,N,N-trimethyl)-homoserine, phosphatidylglycerol, sulfoquinovosyl-diacylglycerol, phosphatidylethanolamine, and phosphatidylinositiol. Their functions in relation to the regulation of cell membrane stability, signal transduction and photosynthesis efficiency under salt stress are also discussed in this paper. This is the first study using UPLC/Q-TOF-MS-based lipidomic profiling with multivariate statistical analysis for lipid biomarkers discovery from microalgae in response to stress conditions.