Abstract
Background Under nitrogen deficiency situation, Nannochloropsis spp. accumulate large amounts of lipid in the form of triacylglycerides (TAG). Several researches have studied the mechanism of this process from the perspective of transcriptome and metabolome, yet proteome analysis on this process is still sparse and lacking the analysis of the dynamic adaption to nitrogen deficiency. Here, proteomes for 03h, 06h, 12h, 24h, 48h and 10th day of nitrogen deplete and replete conditions were compared. New proteome results were integrated with existing transcriptome and other data.Results Obtained results illuminated physiological adaptations not deduced from previous transcriptome data: (a) Abundance of proteins related to photosynthesis only slightly decreased in the first 48h, indicating that photosynthesis is still working efficiently, and protein amounts adjust gradually with reduction in chloroplast size. (b) Most proteins related to the TCA cycle were strongly upregulated after 48h under nitrogen deficiency, suggesting that respiration is enhanced after 48h and that TCA cycle efflux supports the carbon required for lipid synthesis. (c) Proteins related to lipid accumulation via the Kennedy pathway increased their abundance at 48h, synchronous with the previously reported diversification of fatty acids after 48h.Conclusions This study adds a proteome perspective on the major pathways for TAG accumulation by Nannochloropsis due to absence of nitrogen: photosynthesis, membrane lipid conversion, protein degradation, TCA cycle. By integrating existing transcriptome and other data, our research provided for Nannochloropsis oceanica a multi-layered description of adaptation to nitrogen limitation and lipid accumulation. Cluster analysis of this integrated dataset allowed inference of post-transcriptional regulation events.
A Study on the Effect of Macro- and Micro- Nutrients on Nannochloropsis oceanica Growth, Fatty Acid Composition and Magnetic Harvesting Efficiency
