Cloning and characterization of CcEcR - An ecdysone receptor homolog from the Mediterranean fruit fly Ceratitis capitata

In order to understand the role that 20-hydroxyecdysone plays during develo pment of the Mediterranean fruit fly Ceratitis capitata (medfly), a major a gricultural pest, we have cloned a Ceratitis ecdysone receptor (CcEcR) and studied its expression and its binding properties to an ecdysone response e lement. Using the conserved DNA binding region of the Drosophila melanogast er ecdysone receptor (DmEcR) B1 cDNA as a probe, we isolated a medfly cDNA clone containing the coding region, a part of the 5'-untranslated region an d the complete 3'-untranslated region of a CcEcR. The deduced CcEcR polypep tide contained all five domains typical of a nuclear receptor. Alignment co mparisons and phylogenetic analyses indicated that CcEcR most closely resem bled the B1 isoform of DmEcR and Lucilia cuprina EcR homolog (LcEcR) relati ve to all other known ecdysone receptors. In situ hybridization analysis sh owed that the CcEcR gene is mapped in the region 53B of the 4R chromosome a rm, while Northern hybridization analysis showed that CcEcR transcripts hav e a size of approximately 8 kb. Significant levels of CcEcR transcripts wer e detected in eggs, middle and late embryos, late third instar larvae and m iddle prepupae. The levels of the CcEcR transcripts during the other larval stages as well as during pupal and adult stages were much lower, while dur ing the early stages of embryogenesis were very low. Electrophoretic mobili ty shift assays indicated that CcEcR binds specifically to the Drosophila h sp27 ecdysone response element as a heterodimer with Drosophila USP, the pr oduct of the ultraspiracle gene. Our structural and biochemical data sugges t that CcEcR is the functional homolog of the B1 isoform of DmEcR.