title: The rapid divergence of the ecdysone receptor is a synapomorphy for Mecopterida that clarifies the Strepsiptera problem.
abstract: In arthropods, the regulation by ecdysteroids is mediated by the heterodimer between the ecdysone receptor (ECR; NR1H1) and ultraspiracle (USP/RXR; NR2B4) nuclear receptors. Both ECR and USP/RXR ligand-binding domains experienced a strong acceleration of evolutionary rate in Diptera and Lepidoptera, which belong to the superorder Mecopterida. We performed a phylogenetic analysis of 28 ECR and 30 USP/RXR protein sequences from 36 arthropod species, including representatives from Trichoptera, Mecoptera and Siphonaptera. Our data show that the acceleration of ECR and USP/RXR was a unique event in the ancestor of Mecopterida. Our analysis shows further that Strepsiptera ECR and USP/RXR sequences are unambiguously placed outside of the Mecopterida clade. Protein alignments reveal that eight of 11 synapomorphies support an affinity between Strepsiptera and Coleoptera sequences. The affiliation of Strepsiptera to Diptera should therefore be rejected.
authors.affiliation: Laboratoire de Biologie Moléculaire de la Cellule, UMR 5161 du CNRS, INRA LA 1237, IFR128 BioSciences Lyon-Gerland, Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, Lyon, France. Francois.Bonneton@ens-lyon.fr
authors.forename: F
authors.initials: F
authors.lastname: Bonneton
authors.forename: F G
authors.initials: FG
authors.lastname: Brunet
authors.forename: J
authors.initials: J
authors.lastname: Kathirithamby
authors.forename: V
authors.initials: V
authors.lastname: Laudet
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001517:Coleoptera; D004268:DNA-Binding Proteins / Q000235:genetics*; D029721:Drosophila Proteins; D005260:Female; D007313:Insecta / Q000145:classification*; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D011987:Receptors, Steroid / Q000235:genetics*; D017385:Sequence Homology; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D011987:Receptors, Steroid; D014157:Transcription Factors; C066030:USP protein, Drosophila; C055469:ecdysone receptor