Abstract
BackgroundIt is reported that the circadian rhythms of female mating activity differ among Drosophila species and are controlled by an endogenous circadian clock. Here, we found that the mating rhythm of D. ananassae differed from that of D. melanogaster. Moreover, to evaluate the effect of clock gene products on mating activities, we examined the mating activity of D. melanogaster timeless (tim01) transgenic fly harboring heat-shock promotor driven-D. ananassae timeless (tim) gene (hs-AT tim01).MethodsFlies were maintained under light/dark (LD) cycles for several days and then they were transferred to constant dark (DD) conditions at 25°C. Transformant flies were heat-shocked for 30 min (PZT 10.5–11.0 or PZT 22.5–23.0; PZT means Projected Zeitgeber Time) at 37°C every day. Daily expressions of D. ananassae TIMELESS (TIM) protein in transgenic flies were measured by western blotting. To examine whether the timing of D. ananassae TIM protein induction by heat shock can change the patterns of the behavior activities of D. melanogaster tim01 flies, we measured locomotor and mating activity rhythms under DD at 25°C ± 0.5°C except when heat shock was applied.ResultsHeat shock applied at PZT 10.5–11.0 and at PZT 22.5–23.0 induced high TIM levels during subjective night and day, respectively, in hs-AT tim01 flies. The locomotor rhythm of these flies was changed from diurnal to nocturnal by the timing of D. ananassae TIM induction. However, the mating rhythm of these flies could not be entrained by the timing of D. ananassae TIM induction.ConclusionThe pattern of mating activity rhythms of D. ananassae and of D. melanogaster differed. The mating activity rhythms of D. melanogaster tim01 flies harboring hs-AT tim appeared after heat-shock but the pattern and phase differed from those of wild-type D. ananassae and D. melanogaster. Moreover, the mating rhythm of these flies could not be entrained by the timing of D. ananassae TIM induction although the locomotor rhythm of hs-AT tim01 was changed from diurnal to nocturnal according to the timing of D. ananassae TIM induction. These data suggest that species-specific mating activities require output pathways different from those responsible for locomotor rhythms.
Highlights
The behaviors of most organisms are subject to rhythms that are controlled by an endogenous circadian clock [1]
D. ananassae TIM protein was induced by heat shock at PZT 10.5–11.0 (A) and at PZT 22.5–23.0 (B) in w, tim01, hs-D. ananassae tim flies
The dotted lines depict data from non-heat-shocked control flies. (C) and (D) are representative double-plot actgrams of locomotor activitys of transgenic flies that were heat shocked at PZT 10.5–11.0 (C) and PZT 22.5–23.0 (D), respectively
Summary
The behaviors of most organisms are subject to rhythms that are controlled by an endogenous circadian clock [1]. Clock genes of the melon fly may cause reproductive isolation through a change in the time of mating [8]. The rhythms of Drosophila mating behaviors are controlled by circadian clock genes and are especially attributed to the female clock [2]. Female circadian rhythm in mating activity is species-specific, and this might constitute one source of the reproductive isolation that allows Drosophila to avoid sympatric hybridization. The mating behavior rhythms of D. melanogaster and D. simulans are different and in antiphase [2]. It is reported that the circadian rhythms of female mating activity differ among Drosophila species and are controlled by an endogenous circadian clock. We found that the mating rhythm of D. ananassae differed from that of D. melanogaster. To evaluate the effect of clock gene products on mating activities, we examined the mating activity of D. melanogaster timeless (tim01) transgenic fly harboring heat-shock promotor driven-D. ananassae timeless (tim) gene (hs-AT tim01)
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