title: Nuclear receptor HR4 plays an essential role in the ecdysteroid-triggered gene cascade in the development of the hemimetabolous insect Blattella germanica.
abstract: Despite the differences in the developmental strategies between hemimetabolous and holometabolous insects, a common feature between both types of development is that periodic pulses of the steroid hormone 20-hydroxyecdysone (20E) dictate each developmental transition. Although the molecular action of 20E has been extensively studied in holometabolous insects, data on hemimetabolous is scarce. To address this, we have used the German cockroach Blattella germanica to show that 20E signals through a transcriptional cascade of the nuclear hormone receptor-encoding genes BgE75, BgHR3 and BgFTZ-F1. Here, we report the isolation and functional characterization of BgHR4, another nuclear receptor involved in this cascade. Expression studies along with tissue incubations and RNAi experiments show that cross-regulation between BgE75 and BgHR3 directs the expression of BgHR4. Finally, we have also shown that BgHR4 is an essential gene required for successfully completing nymphal-nymphal and nymphal-adult transitions, by allowing the appropriate delay in the induction of BgFTZ-F1.
authors.affiliation: Institute of Evolutionary Biology (CSIC-UPF), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Mané-Padrós
authors.forename: Ferran
authors.initials: F
authors.lastname: Borràs-Castells
authors.forename: Xavier
authors.initials: X
authors.lastname: Belles
authors.forename: David
authors.initials: D
authors.lastname: Martín
mesh_terms: D000818:Animals; D020048:Blattellidae / Q000235:genetics / Q000254:growth & development*; D003001:Cloning, Molecular; D004441:Ecdysterone / Q000378:metabolism*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D053263:Gene Regulatory Networks; D019476:Insect Proteins / Q000502:physiology*; D008969:Molecular Sequence Data; D009758:Nymph / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
chemical_list: D019476:Insect Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D004441:Ecdysterone