Invited resubmission: the Drosophila circadian clock under simulated natural conditions

像人类一样，果蝇，黑腹果蝇，有一个内部的24小时时钟，可以对它的行为和生理进行计时。对于这两种生物体来说，这种时钟的遗传基础实际上是相同的，这两种生物在大脑中也有专门的神经元，在那里表达这些时钟基因。这些神经元产生有节奏的信号，这些信号被传输到大脑的其他区域，并用于产生有节奏的行为。人类和苍蝇之间的这些相似之处意味着，后者是研究时钟分子神经生物学的一个廉价而方便的模型系统。由于时钟对人类的健康和幸福很重要(考虑到长期轮班的工人，他们比一般人更容易出现与健康相关的问题)，对果蝇的时钟研究具有重要的医学意义。我们对飞行时钟的许多了解都是在人工实验室环境中在恒定的温暖温度下收集的，通常是在12小时的光照和12小时的黑暗中，或者在恒定的光照或恒定的黑暗中。虽然简化复杂的自然环境是必要的，但我们也面临着误解时钟在自然界中如何工作的风险。我们花了三年多的时间研究野外飞行的运动节奏，我们的结果表明，我们珍视的一些关于飞行时钟的概念可能需要一些认真的修改。然而，我们不能指望我们的同事经历在野外研究苍蝇行为的痛苦，因为这是非常不便、困难和不可预测的，就元素而言，这些元素让我们任由他们摆布。因此，我们需要在实验室中模拟自然条件，这就是我们的建议所涉及的。我们已经积累了大量关于苍蝇行为的现场数据，针对不同的苍蝇品系、时钟突变以及相关的气象观测，但我们需要现实地模拟任何一种天，热、冷、亮、阴、有月光，没有任何季节。为了做到这一点，我们开发了一种模拟的可编程光源，它可以在几乎任何环境情况下模拟自然光的周期，包括月光、黄昏和光谱的日常变化。这被放在一个可编程的孵化器中，可以类似地模拟任何环境温度周期。在初步研究中，我们已经表明，我们可以常规地复制我们在野外记录的几乎所有意想不到的发现，所以我们知道我们的模拟是现实的。我们现在有了一个独特的机会来研究准自然环境中的复杂行为，我们现在可以尝试使用我们拥有的复杂的苍蝇特有的工具，从行为、遗传和神经生物学上系统地剖析和操纵时钟，并更全面地了解自然环境信号如何调节生物节奏。自然昼夜节律夹带一直是生命进化的一个基本特征，并指导着高等生物体的节律行为和生理。在最近几个世纪，人类的自然缠绕已经被人工缠绕所取代，有充分的证据表明不适应的生理和心理反应。通过评估操纵这些外部信号会干扰哪些行为、分子和神经生物学特征，我们的结果将引起科学界和非科学界的极大兴趣。

Like humans, the fruitfly, Drosophila melanogaster, has an internal 24 hour clock that times its behaviour and physiology. The genetic basis for this clock is practically the same for both organisms, which also have dedicated neurons in the brain in which these clock genes are expressed. These neurons generate rhythmic signals that are transmitted to other regions of the brain and serve to generate rhythmic behaviour. These similarities between humans and flies means that the latter serve as a cheap and convenient model system for studying the molecular neurobiology of clocks. As clocks are important for human health and well-being (consider chronic shift workers, who have higher levels of health-related problems than the general population), clock research in flies has significant medical relevance. Much of what we know about the fly clock has been collected in artificial laboratory environments at constant warm temperatures, usually in 12 hours of light followed by 12 hours of darkness, or in constant light or constant dark. While it is necessary to simplify the complex natural environment, we also run the risk of misunderstanding how clocks might work in nature. We have spent more than three years studying fly locomotor rhythms in the wild, and our results suggest that some of our cherished concepts about the fly clock, might need some serious revision. However, we cannot expect our colleagues to go through the pain of studying fly behaviour in the wild, as it is very inconvenient, difficult, and unpredictable in terms of the elements, which have us at their mercy. Thus, we need to simulate natural conditions in the laboratory, and this is what our proposal is about. We have amassed an enormous amount of field data on fly behaviour, for different fly strains, clock mutants, as well as associated meteorological observations, but we need to realistically mimic any kind of day, hot, cold, bright, overcast, with moonlight, without, in any season. In order to do this, we have developed a simulated programmable light-source which can mimic the natural light cycle in almost any environmental situation, including moonlight, twilights, and the daily changes in the spectrum. This is placed in a programmable incubator that can similarly simulate any environmental temperature cycle. In preliminary studies we have shown that we can routinely replicate almost all of the unexpected findings we have recorded in the wild, so we know our simulations are realistic. We now have an unique opportunity to study a complex behaviour in a quasi-natural setting and we can now attempt to systematically dissect and manipulate the clock, behaviourally, genetically, and neurobiologically, using the sophisticated fly-specific tools we have at our disposal, and understand more completely how natural environmental signals tune up biological rhythms. Natural circadian entrainment has been a fundamental feature of the evolution of life and has guided the rhythmic behaviour and physiology of higher organisms. In recent centuries, natural entrainment in humans has been replaced by artificial entrainment, with ample evidence for maladaptive physiological and psychological responses. By assessing which behavioural, molecular and neurobiological features are disturbed by manipulating these external signals, our results will be of considerable interest to the scientific and lay community.