title: Moonlight shifts the endogenous clock of Drosophila melanogaster.
abstract: The ability to be synchronized by light-dark cycles is a fundamental property of circadian clocks. Although there are indications that circadian clocks are extremely light-sensitive and that they can be set by the low irradiances that occur at dawn and dusk, this has not been shown on the cellular level. Here, we demonstrate that a subset of Drosophila's pacemaker neurons responds to nocturnal dim light. At a nighttime illumination comparable to quarter-moonlight intensity, the flies increase activity levels and shift their typical morning and evening activity peaks into the night. In parallel, clock protein levels are reduced, and clock protein rhythms shift in opposed direction in subsets of the previously identified morning and evening pacemaker cells. No effect was observed on the peripheral clock in the eye. Our results demonstrate that the neurons driving rhythmic behavior are extremely light-sensitive and capable of shifting activity in response to the very low light intensities that regularly occur in nature. This sensitivity may be instrumental in adaptation to different photoperiods, as was proposed by the morning and evening oscillator model of Pittendrigh and Daan. We also show that this adaptation depends on retinal input but is independent of cryptochrome.
authors.affiliation: University of Regensburg, Institute of Zoology, 93040 Regensburg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bachleitner
authors.forename: Lena
authors.initials: L
authors.lastname: Kempinger
authors.forename: Corinna
authors.initials: C
authors.lastname: Wülbeck
authors.forename: Dirk
authors.initials: D
authors.lastname: Rieger
authors.forename: Charlotte
authors.initials: C
authors.lastname: Helfrich-Förster
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D015153:Blotting, Western; D056926:CLOCK Proteins; D002940:Circadian Rhythm / Q000502:physiology*; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000502:physiology*; D008027:Light; D016081:Moon; D009043:Motor Activity / Q000502:physiology; D009687:Nuclear Proteins / Q000378:metabolism; D056950:Period Circadian Proteins; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: C120526:Clk protein, Drosophila; D029721:Drosophila Proteins; D009687:Nuclear Proteins; C539040:PER protein, Drosophila; D056950:Period Circadian Proteins; D014157:Transcription Factors; C096445:tim protein, Drosophila; D056926:CLOCK Proteins