Circadian Clock Control of Seasonal Migration

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Life on earth is subjected to daily and seasonal variations in the timing of sunrise and sunset. To adapt to this rhythmic environment, animals, plants and microbes have evolved circadian clocks that orchestrate daily rhythms of physiology and behavior on a 24-hour basis. Although the role of circadian clocks in driving daily biological rhythms is relatively well known, their role in seasonal responses due to changes in day-length remain unclear. The proposed research aims to understand how animal circadian clocks in the brain regulate seasonal rhythms in behavior and physiology. The objective of this project is to determine the molecular mechanisms through which brain clocks regulate seasonal rhythms in the iconic long-distance migration of the North Eastern American monarch butterfly (Danaus plexippus). The studies will address a fundamental question in chronobiology and will advance our understanding of the molecular mechanisms underlying photoperiodic responses and migratory behavior. This could have broader implications for the conservation of endangered migratory species, and for understanding their adaptive potential to climate change. Through this project, graduate and undergraduate students will be mentored in biological clocks research and molecular genetics. Outreach activities will be conducted with local grade and high schools to introduce students to citizen science by participating in the generation of data on monarch migration patterns and the restoration of their habitat through monarch tagging programs and the creation of new Monarch Waystations. The overarching goal of the proposed research is to uncover the molecular mechanisms underlying clock-controlled seasonal rhythms in long-distance migration of the monarch butterfly. A fundamental understanding of the molecular mechanisms by which seasonal rhythms and photoperiodic responses in animals are regulated by the circadian clock has been hampered by the lack of genomic and genetic tools in non-model species (hamster, sheep, bird) that display robust photoperiodic responses, and the lack of robust photoperiodic responses in genetically tractable animals (fly, mouse). This project will take advantage of powerful molecular, genomic and genetic tools available in the monarch to (i) examine the role of circadian clocks and clock genes in the photoperiodic induction of the migratory behavioral and physiological switch, (ii), identify clock-output genes underlying the migratory switch, and (iii) disrupt candidate genes in vivo to define their impact on migratory behavior and physiology. These experiments will yield unprecedented insight into the molecular bases of insect photoperiodic responses and the genetic program underlying migratory behavior.