Fig. 4.

Overinduction of KaiC arrests the clock at subjective dawn. (A) Ptrc::kaiC cells were cultured in the presence (red) or absence (blue) of 100 μM IPTG from hour 25 (CT 1) for 8 h in LL after 12 h darkness and subjected to microarray analysis. Solid lines show the average mRNA level of the 2 independent experiments shown in dots. Dashed lines show the circadian expression profiles of corresponding genes in wild-type strains. Results for representative subjective dusk genes (kaiC, sigC, cikA), low-amplitude/arrhythmic genes (rpaA, sasA, ldpA) and subjective dawn genes (pilH/rre7, syc1137_d/Synpcc7942_0377, purF) are shown. (B) The expression level of each clock-controlled gene in Ptrc::kaiC cells in the presence of IPTG for 8 h was compared with that in the absence of IPTG at hour 33 in LL. The ordinate indicates the peak time of each of the 800 cycling genes as shown in Fig. 1D. Two hundred sixty-nine cycling genes that show significantly different expression between WT and Ptrc::kaiC cells are plotted on a logarithmic scale as black filled circles (Student's t test; P < 0.05) and the other genes are plotted as gray open circles.