Genetic dissection of seasonal timing in Drosophila

季节节律是大多数生物生存的关键过程，特别是在温带地区。在从植物到哺乳动物的各种物种中，日长的年度变化都受到所谓的光周期时钟的监测，从而能够准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，在秋季发现白天缩短，并转向滞育(一种发育停滞)，这使它们能够存活下来过冬。尽管在过去的80年里，人们对光周期时钟进行了深入的研究，但其潜在的分子机制仍然很大程度上是未知的。这与我们对调节日常节奏的生物钟的理解形成了鲜明对比，在各种模式生物，尤其是果蝇的研究中，已经建立了坚定的原则和丰富的机械细节，包括在不同门中保守的基因。在果蝇中，季节时钟的遗传基础集中在雌性滞育上，表现为短日照和低温导致卵巢发育停滞。不幸的是，这种表型不是很健壮，实际上也不适用于大的基因筛查。最近，我们实验室的研究证实了之前的观察结果，即与在长日照下饲养的果蝇相比，在短日照下发育的果蝇具有显著的耐寒能力。冷反应的差异可以很容易地通过冷昏迷恢复(CCR)试验来量化，在CCR试验中，暴露在冰冻温度下的苍蝇进入可逆性麻醉。恢复时间反映了果蝇对冷的适应程度，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(即在发育期间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，可以监测数百只苍蝇，在这里，我们建议使用这个系统来高通量地对参与光周期反应的基因进行遗传筛选。

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.