Under warm ambient conditions, Drosophila melanogaster suppresses nighttime activity via the neuropeptide pigment dispersing factor

Abstract

Rhythmic locomotor behaviour of flies is controlled by an endogenous time‐keeping mechanism, the circadian clock, and is influenced by environmental temperatures. Flies inherently prefer cool temperatures around 25°C, and under such conditions, time their locomotor activity to occur at dawn and dusk. Under relatively warmer conditions such as 30°C, flies shift their activity into the night, advancing their morning activity bout into the early morning, before lights‐ON, and delaying their evening activity into early night. The molecular basis for such temperature‐dependent behavioural modulation has been associated with core circadian clock genes, but the neuronal basis is not yet clear. Under relatively cool temperatures such as 25°C, the role of the circadian pacemaker ventrolateral neurons (LNvs), along with a major neuropeptide secreted by them, pigment dispersing factor (PDF), has been showed in regulating various aspects of locomotor activity rhythms. However, the role of the LNvs and PDF in warm temperature‐mediated behavioural modulation has not been explored. We show here that flies lacking proper PDF signalling or the LNvs altogether, cannot suppress their locomotor activity resulting in loss of sleep during the middle of the night, and thus describe a novel role for PDF signalling and the LNvs in behavioural modulation under warm ambient conditions. In a rapidly warming world, such behavioural plasticity may enable organisms to respond to harsh temperatures in the environment.

A Subset of Circadian Neurons Expressing dTRPA1 Enables Appropriate Phasing of Activity Rhythms in Drosophila melanogaster Under Warm Temperatures

“…A recent study aimed to identify which circadian neurons respond to temperature by exposing adult flies to a peltier plate maintaining temperatures of 29 or 23 °C, and revealed the temperature sensitivity of the DNs of the circadian circuit via fluorescence changes tagged to endogenous calcium levels (Yadlapalli et al, 2018). Some of our own work has also been able to allude to the role of the LNvs in regulating the allocation of activity levels during the night via PDF signaling under warm LD conditions (Iyengar et al, 2022). We report there that lack of proper PDF signaling and ablated LNvs results in increased activity in the middle of the night under LD30, and we speculate it could be mediated via the DN1s.…”