The mechanism of circadian clock and its influence on animal circannual rhythm.

The circadian clock exists in almost all life forms, and is an internal activity generated by organisms adapting to the daily periodic changes of the external environment. The circadian clock is regulated by the transcription-translation-negative feedback loop in the body, which can regulate the activities of tissues and organs. Its normal maintenance is important for the health, growth, and reproduction of organisms. In contrast, due to the season changes of the environment, organisms have also formed annual cycle physiological changes in their bodies, such as seasonal estrus, etc. The annual rhythm of living things is mainly affected by environmental factors such as photoperiod, and is related to gene expression, hormone content, morphological changes of cell and tissues in vivo. Melatonin is an important signal to recognize the changes of photoperiod, and the circadian clock plays an important role in the pituitary to interpret the signal of melatonin and regulate the changes of downstream signals, which plays an important guiding role in the recognition of annual changes in the environment and the generation of the body's annual rhythm. In this review, we summarize the progress of research on the mechanism of action of circadian clocks in influencing annual rhythms, by introducing the mechanisms of circadian and annual rhythms generation in insects and mammals, and in the context of annual rhythms in birds, with the aim of providing a broader range of ideas for future research on the mechanism of annual rhythms influence.生物钟几乎存在于所有生命体，是生物适应外界环境的每日周期性变化而产生的内部活动。生物钟在体内受转录-翻译-负反馈环路调控，能调节组织、器官的活动，其正常维持对生物的健康、生长、繁殖等具有重要意义。与之相对，由于环境的四季变化，生物也形成了体内的年周期生理变化，如季节性发情、昆虫滞育等。生物的年节律在外部主要受光周期为主的环境因素影响，在体内则与基因表达、激素含量和细胞组织形态的变化有关。褪黑素是识别外部光周期变化的重要信号，而生物钟在垂体解析褪黑素信号并调控下游信号变化中扮演着重要角色，对环境年度变化的识别和机体年节律的产生具有重要指导作用。本文通过介绍昆虫和哺乳动物的昼夜节律和年节律产生的机制，并结合鸟类的年节律，综述了生物钟对年节律产生影响的作用机制研究进展，以期为今后研究年节律的影响机制提供更广泛的思路。.