Abstract
We report identification of a beta-type pigment-dispersing hormone (PDH) identical in two water flea species, Daphnia magna and Daphnia pulex. It has been identified by cloning of precursors, chromatographic isolation from tissue extracts followed by immunoassays and de novo-mass spectrometric sequencing. The peptide is restricted to a complex system of distinct interneurons in the brain and visual ganglia, but does not occur in neurosecretory cells projecting to neurohemal organs as in decapod crustaceans. Thirteen neuron types individually identified and reconstructed by immunohistochemistry were almost identical in terms of positions and projection patterns in both species. Several neurons invade and form plexuses in visual ganglia and major brain neuropils including the central body. Five neuron types show contralateral pathways and form plexuses in the lateral, dorsal, or postlateral brain neuropils. Others are local interneurons, and a tritocerebral neuron connects the protocerebrum with the neuropil of the locomotory second antenna. Two visual ganglia neuron types lateral to the medulla closely resemble insect medulla lateral circadian clock neurons containing pigment-dispersing factor based upon positional and projectional criteria. Experiments under 12:12 h light/dark cycles and constant light or darkness conditions showed significant circadian changes in numbers and activities of one type of medulla lateral PDH neuron with an acrophase in the evening. This simple PDH system shows striking homologies to PDH systems in decapod crustaceans and well-known clock neurons in several insects, which suggests evolutionary conservation of an ancient peptidergic interneuronal system that is part of biological clocks.
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Abbreviations
- a2n1 :
-
Second antenna nerve 1
- BrOG:
-
Brain-optic ganglia complex
- CCAP:
-
Crustacean cardioactive peptide
- CEC:
-
Circumesophageal commissure
- CHH:
-
Crustacean hyperglycemic hormone
- CID:
-
Collision-induced dissociation
- CB:
-
Central body
- CN:
-
Central neuropil
- CNS:
-
Central nervous system
- CT:
-
Circadian time
- DAPI:
-
4′,6′ Diamino-2-phenylindole-2 HCl
- DD:
-
Constant darkness condition
- DN:
-
Dorsal neuropil
- DVM:
-
Diel vertical migration
- ELISA:
-
Enzyme-linked immunosorbent assay
- EPR:
-
Extra-retinal photoreceptor
- EST:
-
Expressed sequence tag
- HPLC:
-
High-pressure lipid chromatography
- IEP:
-
Isoelectric point
- IIF:
-
Indirect immunofluorescence
- La:
-
Lamina
- LD:
-
Light dark conditions
- LL:
-
Constant light condition
- l-LNvs:
-
Large ventral lateral neurons
- LN:
-
Lateral neuropil
- MALDI-TOF:
-
Matrix-assisted laser desorption/ionization-time of flight
- Me:
-
Medulla
- Mel:
-
Medulla lateral neurons
- MLL:
-
Levator labri muscle
- NE:
-
Nauplius eye
- ORF:
-
Open-reading frame
- PAP:
-
Peroxidase anti-peroxidase
- PB:
-
Protocerebral bridge
- PCN:
-
Precentral neuropil
- PDF:
-
Pigment-dispersing factor
- PDH:
-
Pigment-dispersing hormone
- pec:
-
Post-esophageal commissure
- PER:
-
Period gene product
- PLN:
-
Postlateral neuropils
- PPRP:
-
PDH-precursor-related peptide
- RACE:
-
Rapid amplification of cDNA ends
- RPCH:
-
Red pigment-concentrating hormone
- RT:
-
Room temperature
- RT-PCR:
-
Reverse transcription-polymerase chain reaction
- s-LNvs:
-
Small lateral ventral neurons
- SP:
-
Signal peptide
- VNC:
-
Ventral nerve cord
- ZT:
-
Zeitgeber time
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Acknowledgments
The Carl Tryggers Foundation, Stockholm, Sweden (to J.S. and H.D.), the Faculty of Sciences, Stockholm University (to H.D.), the Federal ministry for research and technology, Germany (BMFT, to Q.Z.), and postdoctoral research grants from the Fund for Scientific Research—Flanders, Belgium (F.W.O.-Vlaanderen, to P.V., J.H., K.P.), and the German Research Foundation (DFG to R.P.) are gratefully acknowledged by the authors. We are greatly indebted to Achim Stommel, State office for nature, environment, and customer protection, North-Rhine Westphalia (LaNUV), Bonn, Germany, for providing Daphnia magna and green algae stocks and many useful rearing advises. The authors also wish to thank Dr. S.G. Webster, University of North Wales, Bangor, UK for his generous gift of synthetic Uca-beta-PDH. The authors wish to thank our facility manager Dr. Stina Höglund, Wenner-Gren institute, Stockholm University, for technical help with confocal microscopy, and Dr. Anthony Poole, Department of Molecular Biology and Functional Genomics, Stockholm University, for help with final stylistical polishing of the text.
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Strauß, J., Zhang, Q., Verleyen, P. et al. Pigment-dispersing hormone in Daphnia interneurons, one type homologous to insect clock neurons displaying circadian rhythmicity. Cell. Mol. Life Sci. 68, 3403–3423 (2011). https://doi.org/10.1007/s00018-011-0636-3
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DOI: https://doi.org/10.1007/s00018-011-0636-3