Article

A role for juvenile hormone in the prepupal development of Drosophila melanogaster

Janelia Farm Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA.
Development (Impact Factor: 6.27). 02/2010; 137(7):1117-26. DOI: 10.1242/dev.037218
Source: PubMed

ABSTRACT To elucidate the role of juvenile hormone (JH) in metamorphosis of Drosophila melanogaster, the corpora allata cells, which produce JH, were killed using the cell death gene grim. These allatectomized (CAX) larvae were smaller at pupariation and died at head eversion. They showed premature ecdysone receptor B1 (EcR-B1) in the photoreceptors and in the optic lobe, downregulation of proliferation in the optic lobe, and separation of R7 from R8 in the medulla during the prepupal period. All of these effects of allatectomy were reversed by feeding third instar larvae on a diet containing the JH mimic (JHM) pyriproxifen or by application of JH III or JHM at the onset of wandering. Eye and optic lobe development in the Methoprene-tolerant (Met)-null mutant mimicked that of CAX prepupae, but the mutant formed viable adults, which had marked abnormalities in the organization of their optic lobe neuropils. Feeding Met(27) larvae on the JHM diet did not rescue the premature EcR-B1 expression or the downregulation of proliferation but did partially rescue the premature separation of R7, suggesting that other pathways besides Met might be involved in mediating the response to JH. Selective expression of Met RNAi in the photoreceptors caused their premature expression of EcR-B1 and the separation of R7 and R8, but driving Met RNAi in lamina neurons led only to the precocious appearance of EcR-B1 in the lamina. Thus, the lack of JH and its receptor Met causes a heterochronic shift in the development of the visual system that is likely to result from some cells 'misinterpreting' the ecdysteroid peaks that drive metamorphosis.

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    • "Insect growth and development are controlled by two major hormones, juvenile hormones and ecdysteroids (Delanoue et al., 2010; Kozlova and Thummel, 2003; Riddiford et al., 2010). The titers of both hormones are precisely coordinated by biosynthesis and metabolism pathways and the levels of these hormones are tightly correlated with their regulation of physiological and developmental processes. "
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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.
    Insect Biochemistry and Molecular Biology 08/2014; 54. DOI:10.1016/j.ibmb.2014.08.007 · 3.42 Impact Factor
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    • "Insect growth and development are controlled by two major hormones, juvenile hormones and ecdysteroids (Delanoue et al., 2010; Kozlova and Thummel, 2003; Riddiford et al., 2010). The titers of both hormones are precisely coordinated by biosynthesis and metabolism pathways and the levels of these hormones are tightly correlated with their regulation of physiological and developmental processes. "
    Insect Biochemistry and Molecular Biology 08/2014; · 3.42 Impact Factor
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    • "Met was first identified in a mutagenesis screen for D. melanogaster resistance to the toxic and morphogenetic effects incurred by exposure to the JH analog (JHA) insecticide methoprene (Wilson and Fabian, 1986). The Met 27 null allele confers high-level resistance to methoprene and other JHAs, but not to other classes of insecticides (Wilson and Ashok, 1998; Riddiford et al., 2010). Met 27 mutants display severe reproductive phenotypes (Wilson and Ashok, 1998) but are otherwise viable due to the presence of the functionally redundant paralog gce (Abdou et al., 2011). "
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