A temperature-dependent timing mechanism is involved in the circadian system that drives locomotor rhythms in the fruit fly Drosophila melanogaster.
The circadian clock of Drosophila melanogaster is thought to include rhythmic expression of period gene. Recent studies suggested, however, that a per-less oscillation is also involved in the regulation of circadian locomotor rhythms. In the present study, we examined the existence and the property of the possible per-less oscillation using arrhythmic clock mutant flies carrying per (01), tim(01), dClk(Jrk) or cyc(01), which lack rhythmic per expression. When temperature cycles consisting of 25 degrees C and 30 degrees C with various periods (T=8-32 hr) were given, wild-type (Canton-S) flies showed locomotor rhythms entrained to temperature cycles over a wide range of period (T=8-32 hr) in constant light (LL) while only to T=24 hr in constant darkness (DD). The mutant flies showed rhythms synchronizing with the given cycle both under LL and DD. In per(01) and tim(01) flies, the phase of a major peak slightly changed dependent on Ts in DD, while it did not in dClk(Jrk) and cyc(01) flies. When they were transferred from a constant temperature to a temperature cycle under DD, several cycles were necessary to establish a clear temperature entrainment in per(01) and tim (01) flies. These results suggest that per(01) and tim(01) flies have a temperature-entrainable weak oscillatory mechanism and that the per-less oscillatory mechanism may require dClk and cyc. In addition, per (01) and tim(01) flies changed from thermoactive in DD to cryoactive in LL, while dClk(Jrk) and cyc(01) flies did not. It is thus suggested that dClk and cyc are also involved in determining the light-associated temperature preference in per(01) and tim(01) flies.
Department of Physics, Biology and Informatics, Faculty of Science, Research Institute for Time Studies, Yamaguchi University, Japan.
Taishi
T
Yoshii
Makoto
M
Sakamoto
Kenji
K
Tomioka
D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D002940:Circadian Rhythm; D003624:Darkness; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D025461:Feedback, Physiological; D005786:Gene Expression Regulation; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D008027:Light; D008297:Male; D009043:Motor Activity; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D056950:Period Circadian Proteins; D013696:Temperature; D013997:Time Factors; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D029721:Drosophila Proteins; D019476:Insect Proteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C120526:Clk protein, Drosophila; C539040:PER protein, Drosophila; C112805:cyc protein, Drosophila; C096445:tim protein, Drosophila