Fig. 2: Enrichment analysis of ribosome biosynthesis and photosynthesis genes and gene expression trend of nitrogenase.

a Heatmap analysis showing the DEGs enriched for ribosome biosynthesis (map03010) and (b) for photosynthesis (map00195). Two components of the ribosomal proteins (small subunit, large subunit) and six photosynthetic subunits (photosystem II (PSII), cytochrome, photosystem I (PSI), ATP synthase, allophycocyanin, phycocyanin) were analysed. KEGG annotations were assigned from the genome annotation. Column dendrograms indicate similarity based on Euclidean distance and hierarchical clustering. Gene clusters were determined by k-means clustering with Euclidean distance. The heatmap colour gradient shows low gene expression (blue) and high gene expression (red). c Expression trend of nitrogenase structural genes (nifHDK). Data (TPM, transcripts per million) are presented as box plots (lower bound at 25th percentile, centre line at the median, upper bound at 75th percentile) with whiskers at minimum and maximum values. Shaded-in plots indicate significantly different expression levels of genes and arrows indicate the directionality of statistically significant trends between these two treatments (p < 0.05, right-tailed Fisher’s exact t test followed by Benjamin-Hochberg (BH) adjustment). Statistical significance of selected genes was calculated from pairwise TPM comparisons of triplicate samples. “NaCl” denotes the addition of extra NaCl (18 g/L) to BG11₀, while “None” indicates that no additional substances were added to BG11₀. Source data are provided as a Source Data file.