Functional and regulatory diversification of circadian rhythmperiodgenes during the evolution of vertebrates

Abstract

AbstractThe Period genes (Per) play essential roles in modulating the molecular circadian clock, which regulates the physiological and cellular timing in a broad range of species through the transcription-translation feedback loop in organisms. While the period gene paralogs are widely observed among vertebrates, the evolutionary history and the functional diversification ofPergene paralogs across vertebrates are not well known. In this study, we comprehensively investigated the evolution ofPergenes, their lineage-specific transcriptome landscape and phenotypic effects, and the rapid turnover of transcription binding sites by comparative genomics and transcriptomics. We observed multiple lineage-specific gain and loss events ofPergenes, though there was no simple association observed between ecological factors andPergene numbers in each species. Most salmonid fish species lost theper3gene, while the species that retained theper3gene in salmonid did not the signature of relaxed selective constraint, but rather showed the signature of intensified selection, suggesting essential functional roles of theper3gene in retained species. We also determined the signature of adaptive diversification of the CRY-binding region inPer1andPer3, which modulates the circadian rhythm. Collectively, our findings revealed the evolution ofPergenes and their fine-tuned contribution to the plastic and precise regulation of circadian rhythms in various vertebrate taxa.