Functional conservation of clock output signaling between flies and intertidal crabs

J Biol Rhythms. 2011 Dec;26(6):518-29. doi: 10.1177/0748730411420242.


Intertidal species have both circadian and circatidal clocks. Although the behavioral evidence for these oscillators is more than 5 decades old, virtually nothing is known about their molecular clockwork. Pigment-dispersing hormones (PDHs) were originally described in crustaceans. Their insect homologs, pigment-dispersing factors (PDFs), have a prominent role as clock output and synchronizing signals released from clock neurons. We show that gene duplication in crabs has led to two PDH genes (β-pdh-I and β-pdh-II). Phylogenetically, β-pdh-I is more closely related to insect pdf than to β-pdh-II, and we hypothesized that β-PDH-I may represent a canonical clock output signal. Accordingly, β-PDH-I expression in the brain of the intertidal crab Cancer productus is similar to that of PDF in Drosophila melanogaster, and neurons that express PDH-I also show CYCLE-like immunoreactivity. Using D. melanogaster pdf-null mutants (pdf(01)) as a heterologous system, we show that β-pdh-I is indistinguishable from pdf in its ability to rescue the mutant arrhythmic phenotype, but β-pdh-II fails to restore the wild-type phenotype. Application of the three peptides to explanted brains shows that PDF and β-PDH-I are equally effective in inducing the signal transduction cascade of the PDF receptor, but β-PDH-II fails to induce a normal cascade. Our results represent the first functional characterization of a putative molecular clock output in an intertidal species and may provide a critical step towards the characterization of molecular components of biological clocks in intertidal organisms.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Behavior, Animal / physiology
  • Biological Clocks / physiology*
  • Brachyura / anatomy & histology
  • Brachyura / physiology*
  • Brain / anatomy & histology
  • Brain / metabolism
  • Circadian Rhythm / physiology
  • Drosophila Proteins / classification
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / anatomy & histology
  • Drosophila melanogaster / physiology*
  • Gene Duplication
  • Molecular Sequence Data
  • Neurons / metabolism
  • Neuropeptides / classification
  • Neuropeptides / genetics
  • Neuropeptides / metabolism*
  • Peptides / classification
  • Peptides / genetics
  • Peptides / metabolism*
  • Phenotype
  • Phylogeny
  • Sequence Alignment
  • Signal Transduction / physiology*


  • Drosophila Proteins
  • Neuropeptides
  • Peptides
  • pdf protein, Drosophila
  • melanophore-dispersing hormone