Drosophila circadian rhythms in seminatural environments: Summer afternoon component is not an artifact and requires TrpA1 channels

Abstract

Under standard laboratory conditions of rectangular light/dark cycles and constant warm temperature, Drosophila melanogaster show bursts of morning (M) and evening (E) locomotor activity and a “siesta” in the middle of the day. These M and E components have been critical for developing the neuronal dual oscillator model in which clock gene expression in key cells generates the circadian phenotype. However, under natural European summer conditions of cycling temperature and light intensity, an additional prominent afternoon (A) component that replaces the siesta is observed. This component has been described as an “artifact” of the TriKinetics locomotor monitoring system that is used by many circadian laboratories world wide. Using video recordings, we show that the A component is not an artifact, neither in the glass tubes used in TriKinetics monitors nor in open-field arenas. By studying various mutants in the visual and peripheral and internal thermo-sensitive pathways, we reveal that the M component is predominantly dependent on visual input, whereas the A component requires the internal thermo-sensitive channel transient receptor potential A1 (TrpA1). Knockdown of TrpA1 in different neuronal groups reveals that the reported expression of TrpA1 in clock neurons is unlikely to be involved in generating the summer locomotor profile, suggesting that other TrpA1 neurons are responsible for the A component. Studies of circadian rhythms under seminatural conditions therefore provide additional insights into the molecular basis of circadian entrainment that would otherwise be lost under the usual standard laboratory protocols.

Regulation of sleep plasticity by a thermo-sensitive circuit in Drosophila

“…3a–c). These results were confirmed using a previously validated TrpA1 -RNAi32 transgene to knock down TrpA1 expression throughout the Drosophila nervous system using the pan-neuronal driver elav -GAL4. In the TrpA1 knockdown background, PMW was suppressed (Fig.…”

The sexual dimorphic behaviour of adult Drosophila suzukii: elevated female locomotor activity and loss of siesta is a post-mating response

“…It has recently been shown that adult D. melanogaster display a mid-afternoon (A) peak of activity, but only when the afternoon temperatures reach above 30°C (Das et al, 2015;Green et al, 2015). This thermo-sensitive A peak was seen in simulated natural conditions in a controlled environment incubator where temperatures fluctuated from a low of 17 or 25°C to a peak of 32 or 35°C in the afternoon.…”

“…When the variable light and temperature were out of phase, the A peak coincided with the highest temperature and not peak light levels (Das et al, 2015). Furthermore, the A peak requires a functioning neuronal temperature-sensitive transient receptor potential ion channel (TrpA1) (Das et al, 2015;Green et al, 2015). The afternoon peak of activity recorded for D. suzukii, including that of the mated females, occurred several hours after the hottest period and therefore is not equivalent to the temperature-sensitive A peak of D. melanogaster.…”

Loss of Drosophila melanogaster TRPA1 Function Affects “Siesta” Behavior but Not Synchronization to Temperature Cycles

“…While these findings seem to be at odds with the results reported here (TRPA1 is required for a siesta during warm TCs rather than an increase in activity), it is clear that the experimental conditions are quite different. While we study the function of TRPA1 in light-independent conditions (total darkness), Green et al (2015) use changes of light and temperature. Moreover, it is difficult to compare the results between the studies, because the A peak is not observed in the temperature ranges where we identified a role for TRPA1 in repressing midday activity (20°C : 29°C).…”