Description

The nitrogen depletion stress is widely used to promote energy storage compound (ESC) production of microalgae, such as starch and lipids. Our cultivation results and most reports show that during the nitrogen depletion, the fast ESC’s accumulation happens around the overall nitrogen content lowered to the half of normal cells. It indicates that the cells may take an active nitrogen reassembly to rebalance the requirement of nitrogen, in which the amino acid conversion should play an important role. So here, using a marine strain, Isochrysis zhanjiangensis, as the model to give a detail view on metabolic, transcriptomic and proteomic levels within the “golden period” of ESC’s accumulation. To monitor the metabolic transition in response to nitrogen starvation, the intracellular metabolite fluctuation within 32 h was profiled by GC-MS and LC-MS scanned in selected ion monitoring mode for the first time. These techniques identified and quantified the levels of 14 SMAs, 2 carbohydrates involved in the TCA cycle and glycolysis, and 28 free amino acids (AAs). The pulsed increase of pyruvate, which is the precursor of acetyl-CoA and fatty acids (FAs), indicated a potential to produce more FAs. Although overall AAs showed a decreasing trend under the experimental conditions, Ala and Phe showed increased levels initially. Meanwhile, the transcriptomic and proteomic studies were utilized, and the nitrogen metabolic pathways were studied in this ESC’s fast accumulation period. It is f

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