Kannan Nisha N, Tomiyama Yasuaki, Nose Motoki, Tokuoka Atsushi, Tomioka Kenji
Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan,
Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
Zoolog Sci. 2019 Apr 1;36(2):95-104. doi: 10.2108/zs180148.
Most animals exhibit circadian rhythms in various physiological and behavioral functions regulated by circadian clock that resides in brain and in many peripheral tissues. Temperature cycle is an important time cue for entrainment, even in mammals, since the daily change in body temperature is thought to be used for phase regulation of clocks in peripheral tissues. However, little is known about the mechanisms by which temperature resets the clock. In the present study, we investigated the effect of temperature on circadian activity rhythm and clock gene transcription by using the cricket, . We show that temperature cycle can entrain both behavioral and transcriptional rhythms of clock genes, such as , , and in the circadian pacemaker tissue, optic lobe. Under temperature cycle, phase of evening peak of locomotor activity occurred 1 h before the warm-to-cold phase transition, which is associated with earlier peaks of mRNA expression rhythm of the clock genes than that under light/dark cycles. When the temperature cycle was advanced by 6 h, behavioral rhythms re-entrained to newly phased temperature cycle after ∼16 transient cycles. The mRNA oscillation of and gained stable rhythm under phase advanced temperature cycles with a lesser number of transient cycles than and . These results suggest that temperature cycle can entrain behavioral and molecular rhythms in cricket and clock genes vary in sensitivity to temperature. It is thus likely that clock genes play differential roles in resetting the clock with environmental temperature changes.
大多数动物在由位于大脑和许多外周组织中的生物钟调节的各种生理和行为功能中表现出昼夜节律。温度循环是一种重要的用于同步的时间线索，即使在哺乳动物中也是如此，因为体温的每日变化被认为用于外周组织中生物钟的相位调节。然而，关于温度重置生物钟的机制知之甚少。在本研究中，我们利用蟋蟀研究了温度对昼夜活动节律和生物钟基因转录的影响。我们发现温度循环可以使昼夜起搏器组织视叶中生物钟基因（如 、 、 和 ）的行为节律和转录节律同步。在温度循环条件下，运动活动傍晚峰值的相位在由暖转冷的相变前1小时出现，这与生物钟基因mRNA表达节律的峰值比在光/暗循环条件下出现得更早相关。当温度循环提前6小时时，行为节律在约16个过渡循环后重新同步到新相位的温度循环。在相位提前的温度循环下， 和 的mRNA振荡获得了稳定的节律，其过渡循环的数量比 和 的少。这些结果表明温度循环可以使蟋蟀的行为和分子节律同步，并且生物钟基因对温度的敏感性不同。因此，生物钟基因很可能在随着环境温度变化重置生物钟中发挥不同的作用。
