Abstract
BackgroundIn 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.ResultsTo 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.ConclusionAlthough 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.
Highlights
In crustaceans and insects, development and reproduction are controlled by the steroid hormone, 20-hydroxyecdysone (20E)
The genes obtained from Daphnia encode approximately 500 amino acid open reading frames (ORFs) which is typically for proteins belonging to the cytochrome P450s (CYPs) family [21]
The reason that spo-like genes are more conserved than the other arthropod steroidogenic CYP enzymes is not known, it may be related to the possibility that Spo acts in the rate-limiting Black Box reaction(s) [5,22]
Summary
Development and reproduction are controlled by the steroid hormone, 20-hydroxyecdysone (20E). 20E, is synthesized from cholesterol through reactions involving cytochrome P450s (CYPs). Regulate essential processes during development and reproduction, and are synthesized from cholesterol under the control of steroidogenic enzymes in the cytochrome P450 (CYP) family [1]. A specific biosynthetic pathway yielding 20-hydroxyecdysone (20E), the arthropod molting hormone, evolved, whereas in the line leading to vertebrates, biosynthetic CYPs that produce the vertebrate-type steroids evolved [2]. Drosophila has two spo-like genes, spo and spookier (spok: Cyp307a2) [16] These two genes are close paralogs that are believed to mediate the same enzymatic reaction, at different stages of development
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