Rewitz KF, Gilber LI. Daphnia Halloween genes that encode cytochrome P450s mediating the synthesis of the arthropod molting hormone: Evolutionary implications. BMC Evolutionary Biology

Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280 USA.
BMC Evolutionary Biology (Impact Factor: 3.37). 02/2008; 8(1):60. DOI: 10.1186/1471-2148-8-60
Source: PubMed


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.
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.
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.

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    • "Ecdysteroids play a variety of roles in regulating the growth (in particular molting) and sexual maturation of insects (Parthasarathy et al. 2010; Tennessen and Thummel 2011) and crustaceans (Chá vez et al. 2000; Warren et al. 2002, 2004; Petryk et al. 2003; Niwa et al. 2004; Mykles 2011). Other than in insects, their biosynthetic pathway has only been described in two crustaceans (Rewitz and Gilbert 2008; Sin et al. 2014) and a mite (Cabrera et al. 2015). In both insects and crustaceans, the ecdysteroid 20E is synthesized from dietary cholesterol via cytochrome P450 enzymes encoded by the Halloween genes (Rewitz et al. 2007; Rewitz and Gilbert 2008; Sin et al. 2014; fig. "
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    ABSTRACT: The phylum Arthropoda contains the largest number of described living animal species, with insects and crustaceans dominating the terrestrial and aquatic environments, respectively. Their successful radiations have long been linked to their rigid exoskeleton in conjunction with their specialized endocrine systems. In order to understand how hormones can contribute to the evolution of these animals, here, we have categorized the sesquiterpenoid and ecdysteroid pathway genes in the noninsect arthropod genomes, which are known to play important roles in the regulation of molting and metamorphosis in insects. In our analyses, the majority of gene homologs involved in the biosynthetic, degradative, and signaling pathways of sesquiterpenoids and ecdysteroids can be identified, implying these two hormonal systems were present in the last common ancestor of arthropods. Moreover, we found that the " Broad-Complex " was specifically gained in the Pancrustacea, and the innovation of juvenile hormone (JH) in the insect linage correlates with the gain of the JH epoxidase (CYP15A1/C1) and the key residue changes in the binding domain of JH receptor (" Methoprene-tolerant "). Furthermore, the gain of " Phantom " differentiates chelicerates from the other arthropods in using ponasterone A rather than 20-hydroxyecdysone as molting hormone. This study establishes a comprehensive framework for interpreting the evolution of these vital hormonal pathways in these most successful animals, the arthropods, for the first time.
    Full-text · Article · Jun 2015 · Genome Biology and Evolution
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    • "Additional evidence supporting this comes from the genomic organization of Vdspo which shows the presence of five introns , while that of spook orthologues in insects and crustaceans contain only one to two introns ( Rewitz & Gilbert , 2008 ) . The other two genes Vddib and Vdshd were organized similarly to those of their related orthologues . "
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    ABSTRACT: The ecdysteroid biosynthetic pathway involves sequential enzymatic hydroxylations by a group of enzymes collectively known as Halloween gene proteins. Complete sequences for three Halloween genes, spook (Vdspo), disembodied (Vddib) and shade (Vdshd), were identified in varroa mites and sequenced. Phylogenetic analyses of predicted amino acid sequences for Halloween orthologues showed that the acarine orthologues were distantly associated with insect and crustacean clades indicating that acarine genes had more ancestral characters. The lack of orthologues or pseudogenes for remaining genes suggests these pathway elements had not evolved in ancestral arthropods. Vdspo transcript levels were highest in gut tissues, while Vddib transcript levels were highest in ovary-lyrate organs. In contrast, Vdshd transcript levels were lower overall but present in both gut and ovary-lyrate organs. All three transcripts were present in eggs removed from gravid female mites. A brood cell invasion assay was developed for acquiring synchronously staged mites. Mites within 4 h of entering a brood cell had transcript levels of all three that were not significantly different from mites on adult bees. These analyses suggest that varroa mites may be capable of modifying 7-dehydro-cholesterol precursor and hydroxylations of other steroid precursors, but whether the mites directly produce ecdysteroid precursors and products remains undetermined.
    Full-text · Article · Jun 2015 · Insect Molecular Biology
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    • "It catalyzes 20E into 3-dehydroecdysone reversibly, which is followed by irreversible reduction by 3-dehydroecdysone 3a- reductase to 3-epiecdysone (Chen et al., 1999; Takeuchi et al., 2000). In addition, 26-hydroxylation of 20E mediated by a conserved cytochrome P450 enzyme (CYP18A1) has been reported in Drosophila melanogaster, Spodoptera littoralis and Manduca sexta (Davies et al., 2006; Guittard et al., 2011; Rewitz and Gilbert, 2008). "
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    ABSTRACT: Insect development and metamorphosis are regulated by two major hormones, juvenile hormone and ecdysteroids. Despite being the key regulator of insect developmental transitions, the metabolic pathway of the primary steroid hormone, 20-hydroxyecdysone (20E), especially its inactivation pathway, is still not completely elucidated. A cytochrome P450 enzyme, CYP18A1, has been shown to play key roles in insect steroid hormone inactivation through 26-hydroxylation. Here, we identified two CYP18 (BmCYP18A1 and BmCYP18B1) orthologs in the lepidopteran model insect, Bombyx mori. Interestingly, BmCYP18A1 gene is predominantly expressed in the middle silk gland (MSG) while BmCYP18B1 expresses ubiquitously in B. mori. BmCYP18A1 is induced by 20E in vitro, suggesting its role in 20E metabolism. Using the binary Gal4/UAS transgenic system, we ectopically overexpressed BmCYP18A1 in a MSG-specific manner with a Sericin1-Gal4 (Ser-Gal4) driver or in a ubiquitous manner with an Actin3-Gal4 (A3-Gal4) driver. Ectopic overexpression of BmCYP18A1 in MSG or in all tissues resulted in developmental arrestment of transgenic animals during the final instar larval stage. The 20E titers in the transgenic animals expressing BmCYP18A1 were lower compared to the levels in the control animals. Although the biological significance of MSG-specific expression of BmCYP18A1 is unclear, our results provide the first evidence that BmCYP18A1, which is conserved in most arthropods, is involved in a tissue-specific steroid hormone inactivation in B. mori.
    Full-text · Article · Aug 2014 · Insect Biochemistry and Molecular Biology
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