Evolution of time-keeping mechanisms: early emergence and adaptation to photoperiod
Evolution of time-keeping mechanisms: early emergence and adaptation to photoperiod
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DOI：
10.1098/rstb.2010.0409
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发表时间：
2011-07-27
影响因子：
6.3
通讯作者：
Beersma, D. G. M.
中科院分区：
文献类型：
--
作者：
Hut, R. A.;Beersma, D. G. M.
事实上，所有物种都已发展出细胞振荡和使这些细胞振荡与环境周期同步的机制。这种生物（例如食物供应和捕食风险）或非生物（例如温度和光照）因素的环境循环可能会在每日、每年或潮汐时间尺度上发生。内部计时机制可以促进行为或生理适应环境条件的这种变化。这些计时机制通常涉及内部分子振荡器（“时钟”），通过响应相关环境信号的受体机制（“Zeitgeber”，即德语中的时间给予者）与环境周期同步（“夹带”）。要了解这种计时机制的演变，我们必须了解导致选择性优势的机制。尽管我们在理解驱动内部循环的生理和分子机制（直接问题）方面取得了重大进展，但识别时钟系统自然选择机制（最终问题）的研究相当有限。在这里，我们讨论昼夜节律系统的选择性优势，以及它对日长变化的适应如何在优化季节时间方面发挥功能性作用。我们讨论了昼夜节律计时机制的选择性优势已被证明的各种情况，以及昼夜节律计时暂时丧失可能导致选择性优势的情况。我们对为什么昼夜节律系统出现在蓝藻等原始生命形式中提出了解释，并评估了使这些细菌能够适应昼长季节变化的可能分子机制。我们进一步讨论了昼夜节律系统在光周期时间测量中的作用如何解释当物种暴露于不断变化的气候条件（例如全球变暖）或当它们将其地理范围扩展到不同纬度或海拔时对昼夜节律的差异选择压力。
Virtually all species have developed cellular oscillations and mechanisms that synchronize these cellular oscillations to environmental cycles. Such environmental cycles in biotic (e. g. food availability and predation risk) or abiotic (e. g. temperature and light) factors may occur on a daily, annual or tidal time scale. Internal timing mechanisms may facilitate behavioural or physiological adaptation to such changes in environmental conditions. These timing mechanisms commonly involve an internal molecular oscillator (a 'clock') that is synchronized ('entrained') to the environmental cycle by receptor mechanisms responding to relevant environmental signals ('Zeitgeber', i.e. German for time-giver). To understand the evolution of such timing mechanisms, we have to understand the mechanisms leading to selective advantage. Although major advances have been made in our understanding of the physiological and molecular mechanisms driving internal cycles (proximate questions), studies identifying mechanisms of natural selection on clock systems (ultimate questions) are rather limited. Here, we discuss the selective advantage of a circadian system and how its adaptation to day length variation may have a functional role in optimizing seasonal timing. We discuss various cases where selective advantages of circadian timing mechanisms have been shown and cases where temporarily loss of circadian timing may cause selective advantage. We suggest an explanation for why a circadian timing system has emerged in primitive life forms like cyanobacteria and we evaluate a possible molecular mechanism that enabled these bacteria to adapt to seasonal variation in day length. We further discuss how the role of the circadian system in photoperiodic time measurement may explain differential selection pressures on circadian period when species are exposed to changing climatic conditions (e. g. global warming) or when they expand their geographical range to different latitudes or altitudes.