Journal
MOLECULAR AND CELLULAR ENDOCRINOLOGY
Volume 291, Issue 1-2, Pages 42-49Publisher
ELSEVIER IRELAND LTD
DOI: 10.1016/j.mce.2008.05.006
Keywords
ecdysteroid; metamorphosis; nuclear receptors; gene regulation; ultraspiracle
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Funding
- National Science Foundation [IBN-0421856]
- National Institute of Health [GM070559-03]
- National Research Initiative of the USDA-CSREES [2007-04636]
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Ecdysteroids regulate insect growth and development through a heterodimeric complex of nuclear receptors consisting of ecdysone receptor (EcR) and ultraspiracle (USP). In the red flour beetle, Tribolium castaneum, two isoforms each of EcR and USP have been identified. Quantitative real-time reverse-transcriptase PCR (qRT-PCR) analysis showed isoform-specific developmental expression of both EcR and USP in the epidermis and the midgut dissected from the final instar larvae and pupae. Injection of double-stranded RNA (dsRNA) prepared using the common or isoform-specific regions of EcR or USP as templates caused derailment of development. EcR common region (EcRC) or EcRA dsRNA caused more severe effects, and most of the treated larvae died prior to pupation. EcRB dsRNA caused less severe effects and most of the treated larvae became pupae but showed developmental defects. Only dsRNA prepared against USP common region but not against USDA or USPB isoform-specific region caused developmental defects during larval-pupal metamorphosis. Determination of mRNA levels of EcR isoforms and 20-hydroxyecdysone-response (20E) genes (broad, E75, E74, HR3 and FTZ-F1) by qRT-PCR in the larvae injected with EcRA, EcRB or EcRC dsRNA showed that EcRA initiates ecdysteroid action by regulation the expression of EcRB and 20E-response genes. These data suggest that the EcR but not USP isoforms play distinct roles during the larval-pupal metamorphosis and EcRA plays a dominant role in transduction of ecdysteroid response in T. castaneum. (c) 2008 Elsevier Ireland Ltd. All rights reserved.
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