P4: Localization and interaction of PDF neuropeptides with other members of the circadian clock in representatives of Tardigrada (water bears)
Although numerous studies have focused on members of the circadian clock in arthropods, only little is known about this system in their closest relatives, tardigrades and onychophorans. The aim of this project is therefore to localize the three known homologs of the pigment-dispersing factor neuropeptide (PDF) and their receptor (PDFR) in the tardigrade Hypsibius exemplaris (Fig. 1) using specific antibodies and in situ hybridization, since PDF neuropeptides are known to act as circadian neuromodulators in arthropods. We will analyze the ligand-receptor interactions of PDF-1, PDF-2 and PDF-3 with the respective receptor as well as their influence on the daylight-dependent activities of the animals. We will further identify and localize other potential members of the circadian clock in H. exemplaris that have been intensely studied in insects. Our findings will provide insights into the regulatory mechanisms and the evolution of the circadian system in Panarthropoda (Tardigrada, Onychophora and Arthropoda).
Figure 1: Light micrograph of a specimen of Hypsibius exemplaris (Eutardigrada, Hypsibiidae). From Hering et al. (2016), eLife 5:e11117 (https://doi.org/10.7554/eLife.11117). Scale bar: 20 µm.