Abstract
The central circadian oscillator, kaiABC genes, has been identified in cyanobacterium Synechococcus elongatus PCC 7942. It is proposed that the transcriptional feedback loop involving kaiABC provides a circadian oscillation to each cyanobacterial gene expression. We found these oscillations are able to be classified by two types of amplitude shapes, which are a high amplitude-type and a low amplitude-type. The former expression pattern shows restrict "stop and go" on the transcriptional level during the circadian times. On the other hand, the latter keeps a certain amount of gene expression all the day through, showing a weak circadian oscillation. However, there is no specific cis-element on their promoter region to determine the amplitude shapes. Our micro array data suggested that these oscillation patterns are raised by different mechanisms, and additional experiments provided a new model for circadian output cascade.
