Abstract
Cyanobacteria are the simplest organisms known to exhibit circadian rhythms. Three clock proteins, KaiA, KaiB, and KaiC are essential elements of the circadian clock of cyanobacteria. We demonstrated that the oscillation of KaiC phosphorylation is the primary oscillation of cyanobacterial clock. Thus, kaiC mutants display a wide range of circadian phenotypes. To understand the biochemical functions of KaiC protein, we obtained 900 mutants with PCR-error based mutagenesis followed by a high throughput screening for rhythmic phenotypes with bioluminescence and analyzed their phenotype. While mutations mapped to various locations of KaiC sequence, two clusters of period-altering mutations were found. We analyzed a correlation between the mutation sites and the effects of temperature and light on the period length or phase of the bioluminescence rhythm. We will also discuss on relationships between phenotype of in vivo circadian rhythms and properties of KaiC phosphorylation rhythm of the mutants.
