Table 2.

P-values generated by GSEA (see Materials and methods; Subramanian et al, 2005), designed to test whether genes upregulated under N starvation are enriched for putative NtcA targets

	Time (h)
Strain	0	3	6	12	24	48
MED4	0.2240	0.0002*	0.0002*	0.0002*	0.0002*	0.0002*
MIT9313	0.1852	0.1040	0.0016*	0.1194	0.0780	0.5940

The analysis was carried out using Prochlorococcus genes with the top 15 NtcA rank scores, all of which had orthologs in other cyanobacteria, plus the genes with top 15 rank scores among genes lacking orthologs in other cyanobacteria. This set was compared to all genes ordered by significant upregulation under N starvation. Asterisks/bold P-values indicate statistically significant enrichment as judged by P<0.05/30 (see Materials and methods and GSEA section of Supplementary information).