A temperature-dependent timing mechanism is involved in the circadian system that drives locomotor rhythms in the fruit fly Drosophila melanogaster

Abstract 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 per01, tim01, dClkJrk or cyc01, which lack rhythmic per expression. When temperature cycles consisting of 25°C and 30°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 per01 and tim01 flies, the phase of a major peak slightly changed dependent on Ts in DD, while it did not in dClkJrk and cyc01 flies. When they were transferred from a constant...