Genetic dissection of seasonal timing in Drosophila

季节选择是大多数生物生存的关键过程，尤其是在温带地区。在从植物到哺乳动物的广泛物种中，人们通过所谓的光周期时钟来监测日长每年的变化，从而精确地确定季节反应的时间。例如，许多昆虫，包括许多农业害虫，在秋季察觉到白天的缩短，并转向滞育（发育停滞），这使它们能够在冬季生存。尽管近80年来人们对光周期钟进行了深入的研究，但其潜在的分子机制在很大程度上仍然是未知的。这与我们对调节日常节律的生物钟的理解形成鲜明对比，对各种模式生物，特别是果蝇的研究，已经建立了坚定的原则和丰富的机制细节，包括在不同门中保守的基因。在果蝇中，季节性时钟的遗传基础集中在雌性滞育上，表现为卵巢发育受阻，由短日和低温引起。不幸的是，这种表型不是很健壮，实际上不适合大的遗传筛选。最近，我们实验室的研究证实了之前的观察，即与长日饲养的苍蝇相比，短日饲养的苍蝇具有显著的抗寒性。低温反应的差异可以很容易地通过低温-昏迷恢复（CCR）试验来量化，在这种试验中，暴露于冰冻温度下的果蝇进入可逆的麻醉状态。恢复时间反映了果蝇的冷适应性，我们最近的工作表明，这种反应在很大程度上受光周期的调节（即在发育过程中暴露于短光周期的果蝇表现出较短的恢复时间）。我们设计了一个自动化系统，允许监测数百只苍蝇，在这里我们建议使用该系统进行高通量遗传筛选参与光周期反应的基因。

Seasonal timing is a key process for survival for most organisms, especially in temperate regions. In broad ranges of species, from plants to mammals, the annual change in day-length is monitored the so-called a photoperiodic clock, allowing the accurate timing of the seasonal response. Many insects for example, including numerous agricultural pests, detect the shortening of the day during the autumn and switch to diapause (a developmental arrest), which allow them to survive the winter. Despite intensive study of the photoperiodic clock for the last 80 years, the underlying molecular mechanism is still largely unknown. This is in marked contrast to our understanding of the circadian clock that regulates daily rhythms, where studies in various model organisms, particularly Drosophila, have established firm principles and rich mechanistic detail, including genes conserved across diverse phyla. In Drosophila, the genetic basis of the seasonal clock has focused on female diapause, manifested as a developmental arrest of the ovaries induced by short days and low temperatures. Unfortunately, this phenotype is not very robust, and practically is not amenable for large genetic screens. Recently, research in our laboratory has corroborated previous observations that flies developed under short days become significantly cold-resistant compared with flies raised in long-days. The difference in cold response can be easily quantified using the chill-coma recovery (CCR) assay, in which flies exposed to freezing temperatures enter reversible narcosis . The recovery time reflects how cold-adaptive the flies are, and our recent work has demonstrated that this response is largely regulated by the photoperiod (i.e. flies exposed to short photoperiods during development exhibit shorter recovery times). We have devised an automated system, allowing the monitoring of hundreds of flies, and here we propose to use this system for high-throughput genetic screen for genes involved in the photoperiodicresponse.