Abstract
The central circadian oscillator, kaiABC genes, has been identified in cyanobacterium Synechococcus elongatus PCC 7942. The bona-fide central clock proteins occurs autonomous oscillation in vitro, and it was proposed that the transcriptional feedback loop involving kaiABC expression provides a global circadian expression. As a fact, we have never found non-oscillatory genes from cyanobacteria using luxAB reporter system. In this study, we therefore examined how cyanobacterial genes get such a global expression pattern. A microarray analysis exhibited that only 30% genes had a possible oscillation in the mRNA accumulation level. Additionally, these genes showed negative feedback regulation against excess KaiC but not the others. Thus, the global oscillation of gene expression is not generated in transcriptional level, suggesting it is given in post-transcriptional level like a translation process. According these aspects, we will finally propose new model for circadian output cascade in cyanobacteria.
