Edysone receptor isoforms play distinct roles in controlling molting and metamorphosis in the red flour beetle, Tribolium castaneum

Abstract

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 realtime 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 isoformspecific 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 USPA 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.

Ecdysone receptor in the mud crab Scylla paramamosain: a possible role in promoting ovarian development

“…However, recently alternatively spliced regions in the hinge domain and the ligand-binding domain have also been identified in various crustaceans, including the fiddler crab Uca pugilator (Chung et al 1998a,b, Durica et al 2002, the kuruma prawn Marsupenaeus japonicus (Asazuma et al 2007), the American clawed lobster Homarus americanus (Tarrant et al 2011), the freshwater prawn Macrobrachium nipponense (Shen et al 2013), and the blue crab Callinectes sapidus (Techa & Chung 2013). It has been proposed that different isoforms of EcR had their unique domains, which influence each receptor's ability to activate or repress gene expression, and hence exert different physiological functions (Hopkins et al 2008, Tan & Palli 2008, Schwedes et al 2011.…”

Alternative splicing in the fiddler crab cognate ecdysteroid receptor: Variation in receptor isoform expression and DNA binding properties in response to hormone

“…In addition, Nterminal isoform variants have been identified in a variety of organisms (Kamimura et al, 1997;Wang et al, 2000;Laflamme et al, 2002;Kato et al, 2007) and differential patterns of isoform expression are observed in both vertebrates (Mark et al, 2006) and invertebrates. Expression studies, mutant analysis and rescue experiments in invertebrates suggest that the functional specificity of isoforms is linked to their ability to perform a discrete physiological function (Bender et al, 1997;Schubiger et al, 1998;Schubiger and Truman, 2000;Lee et al, 2000;Choi et al, 2006;Parthasarathy and Palli, 2007;Tan and Palli, 2008).…”

Phenotypic plasticity in threeDaphniagenotypes in response to predator kairomone: evidence for an involvement of chitin deacetylases

“…Using a single clone of D. pulex, Dennis et al (2014) showed a dose-dependent upregulation of the genes EcRb, HR3 and HB2 in response to three different concentrations of Chaoborus kairomone; this represents a pattern of expression that is in good agreement with the juvenoid expression profile. EcRb and HR3 have been shown to be essential for moulting in Tribolium (Tan and Palli, 2008) with EcRb and HR3 being nuclear receptors and HB2 being a haemoglobin gene. Even though our data do not support the involvement of juvenile hormone signalling in neck-teeth induction, EcRb, HB2 and HR3 were not investigated in the present study, which might explain diverging results.…”