Abstract
In the cyanobacterium Synechococcus elongatus, all promoter activities are under the control of the circadian clock in continuous light conditions. Previously, Kucho et al. used PCR-fragment-based DNA microarray to examine genome-wide transcription profiles in Synechocystis and identified 9% of all genes as clock-controlled genes. However, the genome-wide expression in synechococcus in which amplitude and precision of circadian transcription rhythm are much higher, has not been analyzed as far.
We employed high-density oligonucleotide arrays (GeneChip) to examine genome-wide Synechococcus gene expression. Our analysis identified at least 30% of 2,538 possible ORFs as clock-controlled genes. Most of the genes were classified into two groups, one peaking at subjective dawn and the other peaking at subjective dusk. Such circadian control was nullified in kaiABC-null strains. These results are consistent with our previously suggested model (Tomita et al. 2005). Based on these results, we will discuss the genetic network among clock-related genes.
