title: Drosophila circadian rhythms in seminatural environments: Summer afternoon component is not an artifact and requires TrpA1 channels.
abstract: Under standard laboratory conditions of rectangular light/dark cycles and constant warm temperature, Drosophila melanogaster show bursts of morning (M) and evening (E) locomotor activity and a "siesta" in the middle of the day. These M and E components have been critical for developing the neuronal dual oscillator model in which clock gene expression in key cells generates the circadian phenotype. However, under natural European summer conditions of cycling temperature and light intensity, an additional prominent afternoon (A) component that replaces the siesta is observed. This component has been described as an "artifact" of the TriKinetics locomotor monitoring system that is used by many circadian laboratories world wide. Using video recordings, we show that the A component is not an artifact, neither in the glass tubes used in TriKinetics monitors nor in open-field arenas. By studying various mutants in the visual and peripheral and internal thermo-sensitive pathways, we reveal that the M component is predominantly dependent on visual input, whereas the A component requires the internal thermo-sensitive channel transient receptor potential A1 (TrpA1). Knockdown of TrpA1 in different neuronal groups reveals that the reported expression of TrpA1 in clock neurons is unlikely to be involved in generating the summer locomotor profile, suggesting that other TrpA1 neurons are responsible for the A component. Studies of circadian rhythms under seminatural conditions therefore provide additional insights into the molecular basis of circadian entrainment that would otherwise be lost under the usual standard laboratory protocols.
authors.affiliation: Department of Genetics, University of Leicester, Leicester LE1 7RH, United Kingdom;
authors.forename: Edward W
authors.initials: EW
authors.lastname: Green
authors.affiliation: Actual Analytics, Edinburgh EH8 9LE, United Kingdom;
authors.forename: Emma K
authors.initials: EK
authors.lastname: O'Callaghan
authors.affiliation: Department of Genetics, University of Leicester, Leicester LE1 7RH, United Kingdom;
authors.forename: Celia N
authors.initials: CN
authors.lastname: Hansen
authors.affiliation: Venetian Institute of Molecular Medicine, 35129 Padova, Italy;
authors.forename: Stefano
authors.initials: S
authors.lastname: Bastianello
authors.affiliation: Department of Genetics, University of Leicester, Leicester LE1 7RH, United Kingdom;
authors.forename: Supriya
authors.initials: S
authors.lastname: Bhutani
authors.affiliation: Department of Biology, University of Padova, Padova 35131, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Vanin
authors.affiliation: Actual Analytics, Edinburgh EH8 9LE, United Kingdom;
authors.forename: James Douglas
authors.initials: JD
authors.lastname: Armstrong
authors.affiliation: Department of Biology, University of Padova, Padova 35131, Italy.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Costa
authors.affiliation: Department of Genetics, University of Leicester, Leicester LE1 7RH, United Kingdom; cpk@leicester.ac.uk.
authors.forename: Charalambos P
authors.initials: CP
authors.lastname: Kyriacou
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D004330:Drosophila / Q000502:physiology*; D029721:Drosophila Proteins / Q000378:metabolism / Q000502:physiology*; D007473:Ion Channels; D009474:Neurons / Q000378:metabolism; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels / Q000378:metabolism / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins; D007473:Ion Channels; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels; C475684:TrpA1 protein, Drosophila
keywords: Drosophila; afternoon; behavior; circadian; locomotor