The CRYPTOCHROME Photoreceptor Gates PDF Neuropeptide Signaling to Set Circadian Network Hierarchy in Drosophila

Abstract

Summary Circadian clocks in the brain are organized as coupled oscillators that integrate seasonal cues to time daily behaviors. In Drosophila, the PIGMENT DISPERSING FACTOR (PDF) neuropeptide expressing morning (M) and non-PDF evening (E) cells are coupled cell groups important for morning and evening behavior, respectively. Depending on day length, either M- (short days) or E-cells (long days) dictate both morning and evening phase, a phenomenon we term network hierarchy. To examine the role of PDF in light-dark conditions, we examined flies lacking both the PDF receptor (PDFR) and the circadian photoreceptor CRYPTOCHROME (CRY). We found that subsets of E-cells exhibit molecular oscillations antiphase to those of wild-type flies, single cry mutants, or single Pdfr mutants, demonstrating a potent role for PDF in light-mediated entrainment specifically in the absence of CRY. Moreover, evening behavioral phase is more strongly reset by PDF(+) M-cells in the absence of CRY. Based on our findings, we propose that CRY can gate PDF signaling to determine behavioral phase and network hierarchy.

Regulation of Drosophila circadian rhythms by miRNA let-7 is mediated by a regulatory cycle

“…2). Because the lights-on response in LD can mask some of the clock-driven morning behaviour 34 , the first day of DD after LD entrainment was also assessed, and this analysis confirmed the lack of morning anticipation in the let-7 mutants (Fig. 2).…”

NAT1/DAP5/p97 and Atypical Translational Control in the Drosophila Circadian Oscillator

“…Dorsal neurons and large PDF cells maintain lower amplitude clock gene cycling while expression elsewhere in fly heads dampens rapidly during incubation in free-running conditions. The large PDF cells (l-LNv) have a different function: they contribute to light resetting in the late night and probably also play a role in morning locomotor activity (Shang et al 2008;Zhang et al 2009b;Sheeba et al 2010).…”

The hormonal and circadian basis for insect photoperiodic timing

“…The circadian signalling pathway activates many outputs, one of which is PDF, and this neuropeptide is expressed in five large ventral lateral neurons (l-LNvs) and four small lateral neurons (s-LNvs) in each hemisphere. These PDF neurons send axonal projections to the dorsal protocerebrum and the optic lobes [147][148][149][150], and in Pdf mutants, the circadian phenotypes of locomotor activity [150] and adult eclosion are disrupted [115]. The G-protein coupled PDF receptor is also expressed in the PI, suggesting that PDF could signal along the neuroendocrine axis [151,152].…”