Fig. 5
Schematic representation of energy and carbon metabolism pathways showing differential gene expression regulated by the circadian clock in S. elongatus PCC 7942. Colored rectangles show transcriptional responses of metabolic genes, with each rectangle containing four squares representing time points 0 h (20:00 vs. 12:00), 2 h (22:00 vs. 14:00), 4 h (00:00 vs. 16:00), and 8 h (04:00 vs. 20:00). Red boxes indicate upregulation and blue boxes indicate downregulation in subjective night relative to subjective day samples. Nodes represent major metabolites. Solid lines indicate metabolic reactions. Shaded arrows highlight major carbon flux routes: red arrows indicate pathways upregulated during subjective day (CO2 fixation to glycogen storage), blue arrows show pathways upregulated during subjective night (glycogen degradation through central carbon metabolism to acetyl-CoA), and green arrows represent IPTG-induced flux toward sucrose synthesis and export. Dashed lines track the generation and utilization of reducing power (NAD(P)H) during subjective night and day periods. Question marks indicate either putative protein functions or gap-filled reactions where no enzyme has been identified in the PCC 7942 genome. Brief descriptions of metabolites, genes, and proteins are provided below, while expanded descriptions of all pathway components are available in Supplementary Dataset 3