Transcriptomic measurements of Nannochloropsis gaditana CCAP 849/5 at different light intensities. Nannochloropsis gaditana

Nannochloropsis gaditana CCAP 849/5 is a marine unicellular heterokont alga and an emerging reference species for basic research on oleogenic microorganisms with biotechnological relevance. We investigated its physiology, metabolome, lipidome and transcriptome after five days of growth under three different light regimes. Light-dependent alterations are observed in amino acid, isoprenoid, nucleic acid and vitamin biosynthesis, suggesting a deep remodeling in the microalgal metabolism triggered by photoadaptation. We measured higher lipid content in medium and high light than low light. Out of 10,919 total predicted nuclear genes, transcripts of 10,456 genes were detected under the three conditions. A total of 2,354 genes were differentially expressed between low light and medium light grown cells and 4,673 between low light and high light grown cells. In particular, high light intensity is shown to affect lipid biosynthesis, inducing the accumulation of diacylglyceryl-N,N,N-trimethylhomoserine (DGTS) and triacylglycerols (TAGs), together with the up-regulation of genes involved in their biosynthesis. Chloroplast polar lipids are instead decreased. These results highlight the high flexibility of lipid biosynthesis in Nannochloropsis gaditana and lay the foundations for an hypothetical mechanism of regulation of primary carbon partitioning by controlling metabolite allocation at the sub-cellular level. Overall design: Nannochloropsis gaditana CCAP 849/5 cells were cultured in small photobioreactors for 5 days under continuous light at 10, 100, 1000 μmol photons m-2 s-1 at 21 °C. Three biological replicates for each light intensity was collected. The total number of samples is 9.