Abstract

Organisms across all kingdoms of life have evolved circadian clocks to temporally align biological activities with diurnal changes in the environment. In the cyanobacterium Synechococcus elongatus the core oscillator is comprised of the proteins KaiA, KaiB, and KaiC that generate oscillations in the phosphorylation state of KaiC. Time encoded in the phosphorylation state of KaiC is transmitted to the master transcriptional regulator RpaA to generate changes in circadian gene expression. Although the circadian output does not affect growth in constant light conditions, it has substantial effects on fitness in cycling conditions when dark and light periods alternate. In my talk I will describe our findings that reveal why the circadian system is important under cycling conditions and how cellular physiology is altered in these conditions.