title: Temporal Expression of the Clock Genes in the Water Flea Daphnia pulex (Crustacea: Cladocera).
abstract: The timekeeping mechanisms that operate at the core of circadian clocks (oscillators) are based on interacting molecular feedback loops consisting of clock and clock-associated genes. However, there is a lack of comprehensive studies on the expression of clock genes (particularly those forming its core) in single crustacean species at the mRNA and protein levels, and these studies could serve as a basis for constructing a model of the crustacean molecular oscillator. Studies on Daphnia pulex are well suited to fill this gap because this species is the only representative crustacean whose genome has been sequenced. We analyzed the abundance of 20 gene transcripts throughout the day in the whole bodies of D. pulex (single clone); we found that 15 of these genes were transcriptionally active, and most had daily expression level changes. According to the functional classification of their homologues in insects, these genes may represent elements of the Daphnia molecular oscillator core and its input and output pathways. Studies of PERIOD (PER) protein, one of the main clock components, revealed its rhythmic expression pattern in the epidermis, gut, and ovaries. Finally, the cycling levels of many of these clock components observed in animals reared in continuous light led to the conclusion that the Daphnia oscillator, even if it is structurally similar to the oscillators of other arthropods, can be considered a particularly important adaptive mechanism for living in environments with extreme photoperiods.
authors.affiliation: Department of Paleobiology and Evolution, Institute of Zoology, Faculty of Biology, University of Warsaw, Biological and Chemical Research Centre, Warsaw, Poland.
authors.forename: Piotr P
authors.initials: PP
authors.lastname: Bernatowicz
authors.affiliation: Department of Animal Physiology, Institute of Zoology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Kotwica-Rolinska
authors.affiliation: Department of Cell Biology, Nencki Institute of Experimental Biology PAS, Warsaw, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Joachimiak
authors.affiliation: Department of Hydrobiology, Institute of Zoology, Faculty of Biology, University of Warsaw, Biological and Chemical Research Centre, Warsaw, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Sikora
authors.affiliation: Department of Animal Physiology, Institute of Zoology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
authors.forename: Marta A
authors.initials: MA
authors.lastname: Polanska
authors.affiliation: Department of Hydrobiology, Institute of Zoology, Faculty of Biology, University of Warsaw, Biological and Chemical Research Centre, Warsaw, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Pijanowska
authors.affiliation: Department of Animal Physiology, Institute of Zoology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Bębas
mesh_terms: D000818:Animals; D060829:Arthropod Proteins / Q000235:genetics; D002940:Circadian Rhythm; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000235:genetics*; D003621:Daphnia / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D005260:Female; D005786:Gene Expression Regulation; D017440:Photoperiod
chemical_list: D060829:Arthropod Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins