Temporal neuronal control of diapause in the high-latitude fly, Drosophila littoralis.

及时为即将到来的冬天做准备对生存至关重要，尤其是对昆虫这样的小动物。在恶劣的环境条件出现之前，必须及时建立粮食储备，必须停止繁殖，必须提高对寒冷和干旱压力的抵抗力。来自高纬度地区的昆虫在冬季本身就处于滞育状态，在此期间，食物摄入基本停止，新陈代谢急剧降低，寿命延长。夏秋季节白昼长度（光周期）的减少是进入滞育的信号，我们假设昼夜节律钟为测量白昼长度提供了内部参考值。然而，这只在少数昆虫物种中得到了清楚的证明。此外，大脑中的生物钟网络如何与控制滞育的激素中心沟通，在很大程度上是未知的。本项目的目标是：(1)阐明生物钟在北方果蝇中测量日长的功能，该物种表现出强烈的光周期反应，并得到了充分的研究；(2)相对破译生物钟与沿海果蝇和黑腹果蝇的脑间部/外侧部激素中心之间的通信途径。我们发现，两种果蝇的分子钟和生物钟网络都保存得很好，但在神经肽的使用上存在显著差异。这些差异可能解释了北方滨海扁扁蝇强烈的光周期反应。来自芬兰（Kilpisjärvi, 69°N）的果蝇在临界日长约18h时进入滞育，而来自更南部地区（高加索，42°N）的果蝇的行为与黑腹大腹蝇相似，有时在日长12h时仍保持繁殖。有趣的是，在生物钟神经元的神经肽表达和节律行为上，南部滨海夜蛾与黑腹夜蛾都表现出相似之处。这允许在不同纬度的滨海夜蛾的神经肽表达、节律行为和滞育开始的临界日长之间进行相关分析。在此基础上，我们拟模拟北、南滨海扁扁蝇在黑腹扁扁蝇体内神经肽的表达模式，研究转基因扁扁蝇的滞育和节律行为。通过trans-Tango和TANGO-Map MKII将阐明黑腹龙脑侧/脑间部时钟神经元和激素中枢之间的突触和神经肽能连接。最后，我们将利用CRISPR/Cas9在海雀中产生选择的时钟和神经肽基因突变，以阐明生物钟在日长测量中的作用。我们期望我们的研究将有助于我们理解昼夜长度测量和生物钟对冬季休眠的季节性控制。

Timely preparation for the coming winter is essential for survival, especially for small animals such as insects. Food reserves must be built up in good time before the onset of hostile environmental conditions, reproduction must be stopped and resistance to cold and drought stress must be increased. Insects from high-latitudes spend the winter itself in a state of diapause, during which food intake largely ceases, metabolism is drastically lowered, and lifespan is increased. The signal to go into diapause is the decreasing day length (photoperiod) in summer-autumn, and it is assumed that the circadian clock provides the internal reference value for measuring day length. However, this has been clearly demonstrated only for few insect species. Furthermore, it is largely unknown how the circadian clock network in the brain communicates with the hormonal centers controlling diapause. The goal of this project is to (1) elucidate the function of the circadian clock in measuring daylength in the northern fly species Drosophila littoralis, which exhibits a strong and well-studied photoperiodic response, and (2) comparatively decipher the communication pathways between the circadian clock and hormonal centers in the pars intercerebralis/ lateralis in D. littoralis and D. melanogaster. We showed that the molecular clock and clock network are well conserved in both fly species, but that there are striking differences in the use of neuropeptides. These differences may explain the strong photoperiodic response of D. littoralis flies from the north. Flies from Finland (Kilpisjärvi, 69°N) enter diapause at a critical daylength of ~18h, while flies from more southern regions (Caucasus, 42°N) behave similarly to D. melanogaster and sometimes remain reproductive at a daylength of 12h. Interestingly, southern D. littoralis flies show similarities with D. melanogaster in both neuropeptide expression in circadian clock neurons and rhythmic behavior. This allows a correlative analysis between neuropeptide expression, rhythmic behavior, and critical daylength for diapause initiation in D. littoralis flies from different latitudes. Furthermore, we plan to simulate the neuropeptide expression pattern of northern and southern D. littoralis flies in D. melanogaster and investigate diapause and rhythmic behavior in the transgenic flies. The synaptic and neuropeptidergic connections between clock neurons and hormonal centers in the pars intercerebralis/lateralis will be elucidated in D. melanogaster by trans-Tango and TANGO-Map MKII. Ultimately, we will use CRISPR/Cas9 in D. littoralis to generate mutants in selected clock and neuropeptide genes to elucidate the role of the circadian clock in daylength measurement. We expect that our studies will contribute significantly to our understanding of daylength measurement and the seasonal control of winter dormancy by circadian clocks.