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Published on: September 17, 2016
Evolution of kaiA, a key circadian gene of cyanobacteria
Volodymyr Dvornyk1, Qiming Mei2,3
1Department of Life Sciences, College of Science and General Studies, Alfaisal University, Riyadh, 11533, Kingdom of Saudi Arabia. vdvornyk@alfaisal.edu.
Abstract:
The circadian system of cyanobacteria is built upon a central oscillator consisting of three genes, kaiA, kaiB, and kaiC. The KaiA protein plays a key role in phosphorylation/dephosphorylation cycles of KaiC, which occur over the 24-h period. We conducted a comprehensive evolutionary analysis of the kaiA genes across cyanobacteria. The results show that, in contrast to the previous reports, kaiA has an ancient origin and is as old as cyanobacteria. The kaiA homologs are present in nearly all analyzed cyanobacteria, except Gloeobacter, and have varying domain architecture. Some Prochlorococcales, which were previously reported to lack the kaiA gene, possess a drastically truncated homolog. The existence of the diverse kaiA homologs suggests significant variation of the circadian mechanism, which was described for the model cyanobacterium, Synechococcus elongatus PCC7942. The major structural modifications in the kaiA genes (duplications, acquisition and loss of domains) have apparently been induced by global environmental changes in the different geological periods.
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