title: Integration of light and temperature in the regulation of circadian gene expression in Drosophila.
abstract: Circadian clocks are aligned to the environment via synchronizing signals, or Zeitgebers, such as daily light and temperature cycles, food availability, and social behavior. In this study, we found that genome-wide expression profiles from temperature-entrained flies show a dramatic difference in the presence or absence of a thermocycle. Whereas transcript levels appear to be modified broadly by changes in temperature, there is a specific set of temperature-entrained circadian mRNA profiles that continue to oscillate in constant conditions. There are marked differences in the biological functions represented by temperature-driven or circadian regulation. The set of temperature-entrained circadian transcripts overlaps significantly with a previously defined set of transcripts oscillating in response to a photocycle. In follow-up studies, all thermocycle-entrained circadian transcript rhythms also responded to light/dark entrainment, whereas some photocycle-entrained rhythms did not respond to temperature entrainment. Transcripts encoding the clock components Period, Timeless, Clock, Vrille, PAR-domain protein 1, and Cryptochrome were all confirmed to be rhythmic after entrainment to a daily thermocycle, although the presence of a thermocycle resulted in an unexpected phase difference between period and timeless expression rhythms at the transcript but not the protein level. Generally, transcripts that exhibit circadian rhythms both in response to thermocycles and photocycles maintained the same mutual phase relationships after entrainment by temperature or light. Comparison of the collective temperature- and light-entrained circadian phases of these transcripts indicates that natural environmental light and temperature cycles cooperatively entrain the circadian clock. This interpretation is further supported by comparative analysis of the circadian phases observed for temperature-entrained and light-entrained circadian locomotor behavior. Taken together, these findings suggest that information from both light and temperature is integrated by the transcriptional clock mechanism in the adult fly head.
authors.affiliation: Laboratory of Genetics, The Rockefeller University, New York, New York, United States of America.
authors.forename: Catharine E
authors.initials: CE
authors.lastname: Boothroyd
authors.forename: Herman
authors.initials: H
authors.lastname: Wijnen
authors.forename: Felix
authors.initials: F
authors.lastname: Naef
authors.forename: Lino
authors.initials: L
authors.lastname: Saez
authors.forename: Michael W
authors.initials: MW
authors.lastname: Young
mesh_terms: D017398:Alternative Splicing / Q000235:genetics / Q000528:radiation effects; D000818:Animals; D001522:Behavior, Animal / Q000528:radiation effects; D001683:Biological Clocks / Q000528:radiation effects; D002940:Circadian Rhythm / Q000235:genetics* / Q000528:radiation effects*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics* / Q000528:radiation effects; D004777:Environment; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000528:radiation effects*; D017344:Genes, Insect / Q000235:genetics; D008027:Light; D008954:Models, Biological; D009043:Motor Activity / Q000235:genetics / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013696:Temperature
chemical_list: D029721:Drosophila Proteins; D012333:RNA, Messenger