Fig. 4: The timing of natural competence is controlled by the phosphorylation state of KaiC and requires SigF2-dependent expression of DprA.

a Transformation efficiency at 4 time points over a 24-h circadian cycle of ΔkaiC complemented with a mutant kaiC-SE phosphomimetic allele that mimics the dusk phosphorylation state of KaiC. Efficiencies were calculated as the number of antibiotic-resistant colonies per CFU without selection upon transformation of three biologically independent cultures (circles, triangles, and plus signs) and plotted as mean values ± SEM on a square-root scale. b Transformation assays performed on knockout and complemented strains of sigF2. WT S. elongatus PCC 7942 with and without added eDNA served as controls. The assay was performed using three independent clones for each strain, which yielded similar results. c Expression analysis of selected T4PM and competence genes in a sigF2 knockout strain, a sigF2 complemented strain, and a WT control measured by RT-qPCR on cultures collected 2 h after circadian dusk with cells that went into the dark at ZT 12 or were maintained in light. Fold-changes were calculated as 2^−∆∆Ct in dark relative to light conditions for three biologically independent cultures (circles, triangles, and plus signs) of each strain and plotted as mean values ± SEM. The expression of sigF2 by RT-qPCR was not determined (ND) in the sigF2 knockout and sigF2 complemented strains. Source data are provided as a Source Data file.