Transcriptomic and fatty acid analyses of Neochloris aquatica grown under different nitrogen concentration

In this study, we characterized the fatty acid production in Neochloris aquatica at transcriptomics and biochemical levels under limiting, normal, and excess nitrate concentrations in different growth phases. At the stationary phase, N. aquatica mainly produced saturated fatty acids such as stearic acid under the limiting nitrate concentration, which is suitable for biodiesel production. However, it produced polyunsaturated fatty acids such as alpha-linolenic acid under the excess nitrate concentration, which has nutritional values as food supplements. In addition, RNA-seq was employed to identify genes and pathways that were being affected in N. aquatica for three growth phases in the presence of the different nitrate amounts. Genes that are responsible for the production of saturated fatty acids were upregulated in the cells grown under a limiting nitrogen amount while genes that are responsible for the production of polyunsaturated fatty acid were upregulated in the cells grown under excess nitrogen amount. Further analysis showed more genes differentially expressed (DEGs) at the logarithmic phase in all conditions while a relatively steady trend was observed during the transition from the logarithmic phase to the stationary phase under limiting and excess nitrogen. Our results provide a foundation for identifying developmentally important genes and understanding the biological processes in the different growth phases of the N. aquatica in terms of biomass and lipid production.

Automated summary

In this study, the production of fatty acids in Neochloris aquatica under different nitrate concentrations and growth phases was characterized at the transcriptomics and biochemical levels. The results showed that N. aquatica primarily produced saturated fatty acids under limiting nitrate concentrations, suitable for biodiesel production, and produced polyunsaturated fatty acids under excess nitrate concentrations, which have nutritional value as food supplements. RNA-seq analysis identified genes and pathways affected by nitrate concentrations during the three growth phases. Genes involved in saturated fatty acid production were upregulated under limiting nitrogen conditions, while genes responsible for polyunsaturated fatty acid production were upregulated under excess nitrogen conditions. Additionally, more differentially expressed genes were observed during the logarithmic growth phase, and a relatively steady trend was observed during the transition from the logarithmic phase to the stationary phase under limiting and excess nitrogen conditions. These findings provide insights into the developmentally important genes and biological processes involved in biomass and lipid production in different growth phases of N. aquatica.