Figure 6.

Dose-response expression of nitrogen assimilation genes following treatment with increasing concentrations of NO^•. A, Gene differential expression after treatments with NO^•. Phaeodactylum cells were treated with 0 (control), 3, and 10 µm NO^• using a calibrated NO^•-saturated aqueous solution and after 96 h of NO^• treatment, RNA was extracted and subjected to a RNAseq analysis. Libraries for each sample were prepared for stranded 100-bp paired end sequencing and samples were combined and analyzed in a single Illumina HisEquation 2000 lane. Reads were mapped on the most recent genome version of Phaeodactylum tricornutum (http://protists.ensembl.org/Phaeodactylum_tricornutum). Annotated genes coding for nitrogen assimilation were then used to probe changes in three metabolic modules, that is, nitrogen assimilation, integration of nitrogen into amino acids, and integration of nitrogen via the Orn-urea pathway (or cycle). NOA expression was also examined. Eventually, genes with some sequence similarity with genes acting in NO^• signaling in other organisms were also included, although this function seems unlikely based on our study. B, Pathways of nitrogen assimilation and incorporation into amino acids up-regulated by NO^•.