title: Identification of putative circadian clock genes in the American horseshoe crab, Limulus polyphemus.
abstract: While the American horseshoe crab, Limulus polyphemus, has robust circadian and circatidal rhythms, virtually nothing is known about the molecular basis of these rhythms in this species or any other chelicerate. In this study, next generation sequencing was used to assemble transcriptomic reads and then putative homologs of known core and accessory circadian genes were identified in these databases. Homologous transcripts were discovered for one circadian clock input gene, five core genes, 22 accessory genes, and two possible output pathways. Alignments and functional domain analyses showed generally high conservation between the putative L. polyphemus clock genes and homologs from Drosophila melanogaster and Daphnia pulex. The presence of both cry1 and cry2 in the L. polyphemus transcriptome would classify its system as an "ancestral", type 2 clock system. In addition, a novel duplication of CYCLE, and a novel triplication of PERIOD were found. Investigations are currently underway to determine if any of these "circadian" genes also participate in the molecular processes that drive the Limulus circatidal clock.
authors.affiliation: Department of Genetics, Dartmouth, College Hanover, NH 03755, USA. Electronic address: Kevin.N.Chesmore.GR@dartmouth.edu.
authors.forename: Kevin N
authors.initials: KN
authors.lastname: Chesmore
authors.affiliation: Department of Biological Sciences, University of New Hampshire, Durham, NH 03824, USA.
authors.forename: Winsor H
authors.initials: WH
authors.lastname: Watson
authors.affiliation: Department of Biological Sciences, MSC#64, Plymouth State University, Plymouth, NH 03264, USA.
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Chabot
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D056926:CLOCK Proteins / Q000235:genetics*; D057906:Circadian Clocks / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D023281:Genomics; D059014:High-Throughput Nucleotide Sequencing / Q000379:methods*; D006737:Horseshoe Crabs / Q000235:genetics* / Q000254:growth & development; D058977:Molecular Sequence Annotation; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D059467:Transcriptome
chemical_list: D056926:CLOCK Proteins
keywords: Illumina; biological rhythm; chelicerate; circadian; circatidal; clock; clock genes; de novo; horseshoe crab; transcriptome