title: Real-time iTRAQ-based proteome profiling revealed the central metabolism involved in nitrogen starvation induced lipid accumulation in microalgae.
abstract: To understand the post-transcriptional molecular mechanisms attributing to oleaginousness in microalgae challenged with nitrogen starvation (N-starvation), the longitudinal proteome dynamics of Chlorella sp. FC2 IITG was investigated using multipronged quantitative proteomics and multiple reaction monitoring assays. Physiological data suggested a remarkably enhanced lipid accumulation with concomitant reduction in carbon flux towards carbohydrate, protein and chlorophyll biosynthesis. The proteomics-based investigations identified the down-regulation of enzymes involved in chlorophyll biosynthesis (porphobilinogen deaminase) and photosynthetic carbon fixation (sedoheptulose-1,7 bisphosphate and phosphoribulokinase). Profound up-regulation of hydroxyacyl-ACP dehydrogenase and enoyl-ACP reductase ascertained lipid accumulation. The carbon skeletons to be integrated into lipid precursors were regenerated by glycolysis, β-oxidation and TCA cycle. The enhanced expression of glycolysis and pentose phosphate pathway enzymes indicates heightened energy needs of FC2 cells for the sustenance of N-starvation. FC2 cells strategically reserved nitrogen by incorporating it into the TCA-cycle intermediates to form amino acids; particularly the enzymes involved in the biosynthesis of glutamate, aspartate and arginine were up-regulated. Regulation of arginine, superoxide dismutase, thioredoxin-peroxiredoxin, lipocalin, serine-hydroxymethyltransferase, cysteine synthase, and octanoyltransferase play a critical role in maintaining cellular homeostasis during N-starvation. These findings may provide a rationale for genetic engineering of microalgae, which may enable synchronized biomass and lipid synthesis.
authors.affiliation: Department of Biosciences and Bioengineering, Wadhwani Research Center for Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, Maharashtra, India.
authors.forename: Vineeta
authors.initials: V
authors.lastname: Rai
authors.affiliation: Department of Biosciences and Bioengineering, Centre for Energy, Indian Institute of Technology Guwahati, Assam 781039, India.
authors.forename: Muthusivaramapandian
authors.initials: M
authors.lastname: Muthuraj
authors.affiliation: Centre for Research in Nanotechnology &Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
authors.forename: Mayuri N
authors.initials: MN
authors.lastname: Gandhi
authors.affiliation: Department of Biosciences and Bioengineering, Centre for Energy, Indian Institute of Technology Guwahati, Assam 781039, India.|DBT PAN IIT Centre for Bioenergy, Indian Institute of Technology Bombay, Mumbai, Powai - 400067, India.
authors.forename: Debasish
authors.initials: D
authors.lastname: Das
authors.affiliation: Department of Biosciences and Bioengineering, Wadhwani Research Center for Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, Maharashtra, India.|DBT PAN IIT Centre for Bioenergy, Indian Institute of Technology Bombay, Mumbai, Powai - 400067, India.
authors.forename: Sanjeeva
authors.initials: S
authors.lastname: Srivastava
mesh_terms: D002708:Chlorella / Q000378:metabolism*; D020869:Gene Expression Profiling; D050356:Lipid Metabolism; D058086:Microalgae / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics / Q000379:methods; D015398:Signal Transduction
chemical_list: D020543:Proteome; D009584:Nitrogen