关键词: 生物钟, 夜行性哺乳动物, Per1基因, 昼夜节律, 适应性进化

Abstract: For a long time, research on circadian clock has been a hot topic in the field of life science. Previous studies have shown that the core clock gene Per1 is widely involved in the regulation of mammalian circadian rhythms. However, limited understanding of the adaptive sites evolved in the sequence of Per1 gene. And whether these adaptive alterations may promote the formation and stabilization of mammalian diurnal activity patterns remains to be investigated. In this study, we conducted in-depth molecular evolution analyses of the core clock gene Per1 through the real-time quantitative PCR, gene cloning sequencing and molecular evolution analysis. We have identified the circadian oscillation patterns of Per1 gene expressed in the brain of bats, from rest state to sleep state corresponding with the expression level of Per1 gene changed from high to low, and the sleep state showing the lowest expression level, while from wake state to active state, its expression level increased continuously, which was highly correlated with the maintenance of the central biological clock regulation function of Per1 gene. There were 15 potential and 2 significant positively selected sites were detected on the Per1 gene sequence, and one of the significant positively selected sites, 1118A amino acid site detected in nocturnal animals was found to be located on the functional domain of the gene encoded protein sequence. We also found that the evolution rate of Per1 gene in nocturnal mammals was generally higher than that in diurnal mammals, indicating that the core clock gene Per1 experienced strong selective pressures during the evolution of nocturnal mammals, further promoted the formation and stabilization of nocturnal activity patterns in mammals. This study provides a new understanding of the key molecular basis of mammalian homeostasis maintenance and adaptation to the periodically changing environmental conditions, and provides ideas and references for circadian clock related studies.

Key words: Circadian clock, Nocturnal mammals, Per1 gene, Circadian rhythms, Adaptive evolution