Stanton Daniel, Justin Hannah S, Reitzel Adam M
Department of Animal Sciences, University of Florida, Gainesville, FL 32608, USA.
Department of Biological Sciences, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte NC 28223, USA.
Integr Comp Biol. 2022 Dec 30;62(6):1503-1518. doi: 10.1093/icb/icac140.
Over the past few decades, the molecular mechanisms responsible for circadian phenotypes of animals have been studied in increasing detail in mammals, some insects, and other invertebrates. Particular circadian proteins and their interactions are shared across evolutionary distant animals, resulting in a hypothesis for the canonical circadian clock of animals. As the number of species for which the circadian clockwork has been described increases, the circadian clock in animals driving cyclical phenotypes becomes less similar. Our focus in this review is to develop and synthesize the current literature to better understand the antiquity and evolution of the animal circadian clockwork. Here, we provide an updated understanding of circadian clock evolution in animals, largely through the lens of conserved genes characterized in the circadian clock identified in bilaterian species. These comparisons reveal extensive variation within the likely composition of the core clock mechanism, including losses of many genes, and that the ancestral clock of animals does not equate to the bilaterian clock. Despite the loss of these core genes, these species retain circadian behaviors and physiology, suggesting novel clocks have evolved repeatedly. Additionally, we highlight highly conserved cellular processes (e.g., cell division, nutrition) that intersect with the circadian clock of some animals. The conservation of these processes throughout the animal tree remains essentially unknown, but understanding their role in the evolution and maintenance of the circadian clock will provide important areas for future study.
在过去几十年里，负责动物昼夜节律表型的分子机制在哺乳动物、一些昆虫和其他无脊椎动物中得到了越来越详细的研究。特定的昼夜节律蛋白及其相互作用在进化关系较远的动物中是共有的，这就产生了一种关于动物经典昼夜节律钟的假说。随着已描述昼夜节律机制的物种数量增加，驱动周期性表型的动物昼夜节律钟变得越来越不相似。我们在这篇综述中的重点是发展和综合当前的文献，以更好地理解动物昼夜节律机制的古老性和进化。在这里，我们主要通过两侧对称动物中昼夜节律钟所特有的保守基因，对动物昼夜节律钟的进化提供了一个更新的认识。这些比较揭示了核心生物钟机制可能的组成部分存在广泛差异，包括许多基因的丢失，并且动物的祖先生物钟并不等同于两侧对称动物的生物钟。尽管这些核心基因丢失了，但这些物种仍保留着昼夜节律行为和生理机能，这表明新的生物钟已经多次进化。此外，我们强调了一些与某些动物的昼夜节律钟相互交叉的高度保守的细胞过程（如细胞分裂、营养）。这些过程在整个动物谱系中的保守性基本上还不清楚，但了解它们在昼夜节律钟的进化和维持中的作用将为未来的研究提供重要领域。
