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Open Access Research article

Daphnia Halloween genes that encode cytochrome P450s mediating the synthesis of the arthropod molting hormone: Evolutionary implications

Kim F Rewitz1 and Lawrence I Gilbert2*

Author Affiliations

1 Department of Science, Systems and Models, Roskilde University, Postbox 260, DK-4000 Roskilde, Denmark

2 Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280 USA

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BMC Evolutionary Biology 2008, 8:60  doi:10.1186/1471-2148-8-60

Published: 25 February 2008

Abstract

Background

In crustaceans and insects, development and reproduction are controlled by the steroid hormone, 20-hydroxyecdysone (20E). Like other steroids, 20E, is synthesized from cholesterol through reactions involving cytochrome P450s (CYPs). In insects, the CYP enzymes mediating 20E biosynthesis have been identified, but evidence of their probable presence in crustaceans is indirect, relying solely on the ability of crustaceans to synthesize 20E.

Results

To investigate the presence of these genes in crustaceans, the genome of Daphnia pulex was examined for orthologs of these genes, the Halloween genes, encoding those biosynthetic CYP enzymes. Single homologs of spook-CYP307A1, phantom-CYP306A1, disembodied-CYP302A1, shadow-CYP315A1 and shade-CYP314A1 were identified in the Daphnia data base. Phylogenetic analysis indicates an orthologous relationship between the insect and Daphnia genes. Conserved intron/exon structures and microsynteny further support the conclusion that these steroidogenic CYPs have been conserved in insects and crustaceans through some 400 million years of evolution.

Conclusion

Although these arthropod steroidogenic CYPs are related to steroidogenic CYPs in Caenorhabditis elegans and vertebrates, the data suggest that the arthropod steroidogenic CYPs became functionally specialized in a common ancestor of arthropods and are unique to these animals.