Abstract

The Nannochloropsis genus contains oleaginous microalgae that have served as model systems for developing renewable biodiesel. Recent genomic and transcriptomic studies on Nannochloropsis species have provided insights into the regulation of lipid production in response to nitrogen stress. Previous studies have focused on the responses of Nannochloropsis species to short-term nitrogen stress, but the effect of long-term nitrogen deprivation remains largely unknown. In this study, physiological and proteomic approaches were combined to understand the mechanisms by which Nannochloropsis oceanica IMET1 is able to endure long-term nitrate deprivation and its ability to recover homeostasis when nitrogen is amended. Changes of the proteome during chronic nitrogen starvation espoused the physiological changes observed, and there was a general trend toward recycling nitrogen and storage of lipids. This was evidenced by a global down-regulation of protein expression, a retained expression of proteins involved in glycolysis and the synthesis of fatty acids, as well as an up-regulation of enzymes used in nitrogen scavenging and protein turnover. Also, lipid accumulation and autophagy of plastids may play a key role in maintaining cell vitality. Following the addition of nitrogen, there were proteomic changes and metabolic changes observed within 24 h, which resulted in a return of the culture to steady state within 4 d. These results demonstrate the ability of N. oceanica IMET1 to recover from long periods of nitrate deprivation without apparent detriment to the culture and provide proteomic markers for genetic modification.

Highlights

  • IntroductionSilva et al (2009) reported that in the marine cryptophyte Rhodomonas sp., nitrogen starvation triggered a rapid decline in hydrosoluble proteins, photosynthetic pigments, and photosynthetic efficiency, and an increase in total carbohydrate content, suggesting that protein nitrogen from biliproteins was mobilized

  • An inorganic pyrophosphatase involved in lipid degradation was increased, together with a sharp reduction of fatty acid content during the recovery (Fig. 7B, 9 and Table S2). These results suggest that fatty acid oxidation might provide the energy for this metabolic shift during N recovery whereas acetyl-CoA could be shifted to the tricarboxylic acid (TCA) cycle

  • We demonstrate here that marine microalga N. oceanica IMET1 evolves a series of physiological strategies to survive the long-term nitrogen stress

Read more

Summary

Introduction

Silva et al (2009) reported that in the marine cryptophyte Rhodomonas sp., nitrogen starvation triggered a rapid decline in hydrosoluble proteins, photosynthetic pigments, and photosynthetic efficiency, and an increase in total carbohydrate content, suggesting that protein nitrogen from biliproteins was mobilized. Taken together, these studies may suggest that the reduced photosynthesis is a common response of many eukaryotic algae to nitrogen starvation. For Nannochloropsis, it has been reported that nitrogen shortage can lead to significant accumulation of saturated and monounsaturated fatty acids (Hu and Gao, 2006) These fatty acids are mainly associated with storage triacylglycerols, the preferred substrate for biodiesel production. In order to maximize the yield of valuable products from microalgae it is essential to first describe the mechanisms behind the changes in photosynthesis, fatty acid composition, and lipid accumulation on a molecular level

Results
Discussion
Conclusion

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.