title: Exquisite light sensitivity of Drosophila melanogaster cryptochrome.
abstract: Drosophila melanogaster shows exquisite light sensitivity for modulation of circadian functions in vivo, yet the activities of the Drosophila circadian photopigment cryptochrome (CRY) have only been observed at high light levels. We studied intensity/duration parameters for light pulse induced circadian phase shifts under dim light conditions in vivo. Flies show far greater light sensitivity than previously appreciated, and show a surprising sensitivity increase with pulse duration, implying a process of photic integration active up to at least 6 hours. The CRY target timeless (TIM) shows dim light dependent degradation in circadian pacemaker neurons that parallels phase shift amplitude, indicating that integration occurs at this step, with the strongest effect in a single identified pacemaker neuron. Our findings indicate that CRY compensates for limited light sensitivity in vivo by photon integration over extraordinarily long times, and point to select circadian pacemaker neurons as having important roles.
authors.affiliation: University of Virginia, Department of Biology, Charlottesville, Virginia, USA.
authors.forename: Pooja
authors.initials: P
authors.lastname: Vinayak
authors.forename: Jamie
authors.initials: J
authors.lastname: Coupar
authors.forename: S Emile
authors.initials: SE
authors.lastname: Hughes
authors.forename: Preeya
authors.initials: P
authors.lastname: Fozdar
authors.forename: Jack
authors.initials: J
authors.lastname: Kilby
authors.forename: Emma
authors.initials: E
authors.lastname: Garren
authors.forename: Taishi
authors.initials: T
authors.lastname: Yoshii
authors.forename: Jay
authors.initials: J
authors.lastname: Hirsh
mesh_terms: D000818:Animals; D057906:Circadian Clocks / Q000235:genetics; D002940:Circadian Rhythm / Q000235:genetics* / Q000502:physiology; D056931:Cryptochromes / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics* / Q000502:physiology; D005136:Eye Proteins / Q000235:genetics*; D009154:Mutation; D009474:Neurons / Q000378:metabolism; D017785:Photons; D017440:Photoperiod; D020795:Photophobia / Q000235:genetics*; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology
chemical_list: D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; C119828:cry protein, Drosophila