A proposal for robust temperature compensation of circadian rhythms
A proposal for robust temperature compensation of circadian rhythms
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DOI：
10.1073/pnas.0601378104
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发表时间：
2007-01-23
影响因子：
11.1
通讯作者：
Tyson, John J.
中科院分区：
文献类型：
--
作者：
Hong, Christian I.;Conrad, Emery D.;Tyson, John J.
细胞和生物体的内部昼夜节律使其生理特性与地球上普遍存在的24小时光暗周期相协调。产生昼夜节律的机制具有四个定义特征：它们以接近24小时的周期内源性振荡，夹带外部信号，受到异常光脉冲或温度的相移，以及补偿10摄氏度或更高范围内的温度变化。大多数对昼夜节律的理论描述都认为，潜在的机制会产生一个稳定的极限环振荡（在恒定的黑暗或昏暗的光线下），因为极限环很自然地具有昼夜节律的前三个定义属性。另一方面，极限环振荡器的周期通常对随温度显著增加的动力学速率常数非常敏感。因此，温度补偿不是极限环振荡的一般性质，而是必须由温度相关效应的某种微妙平衡来施加。然而，“微妙的平衡”不太可能对突变具有鲁棒性。另一方面，如果昼夜节律产生于一种将敏感性集中在几个速率常数上的机制，那么“平衡行为”可能会更强大，更可进化。我们提出了一个开关式的昼夜节律机制，集中在两个参数的周期敏感性，迫使系统之间的交替稳定的稳态和稳定的极限环。
The internal circadian rhythms of cells and organisms coordinate their physiological properties to the prevailing 24-h cycle of light and dark on earth. The mechanisms generating circadian rhythms have four defining characteristics: they oscillate endogenously with period close to 24 h, entrain to external signals, suffer phase shifts by aberrant pulses of light or temperature, and compensate for changes in temperature over a range of 10 degrees C or more. Most theoretical descriptions of circadian rhythms propose that the underlying mechanism generates a stable limit cycle oscillation (in constant darkness or dim light), because limit cycles quite naturally possess the first three defining properties of circadian rhythms. On the other hand, the period of a limit cycle oscillator is typically very sensitive to kinetic rate constants, which increase markedly with temperature. Temperature compensation is therefore not a general property of limit cycle oscillations but must be imposed by some delicate balance of temperature dependent effects. However, "delicate balances" are unlikely to be robust to mutations. On the other hand, if circadian rhythms arise from a mechanism that concentrates sensitivity into a few rate constants, then the "balancing act" is likely to be more robust and evolvable. We propose a switch-like mechanism for circadian rhythms that concentrates period sensitivity in just two parameters, by forcing the system to alternate between a stable steady state and a stable limit cycle.