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Communication Dans Un Congrès Année : 2010

Evolution of nuclear receptors in insects

Evolution des récepteurs nucléaires chez les insectes

Résumé

In insects, the nuclear receptor family comprises 19 transcription factors, among which a majority play a crucial role in ecdysteroid signaling, notably the receptor of ecdysone itself (ECR). A small network of regulators that control the ecdysone cascade during the onset of metamorphosis underwent an increase of evolutionary rate in a large group of insects, Mecopterida (1/3 of insect species), which includes Diptera and Lepidoptera. This network contains at least five nuclear receptors that probably coevolved together: ECR, USP, HR3, E75 and HR4. By comparing sequences and structures between Drosophila and a non-Mecopterida species, the flour beetle Tribolium castaneum, we try to understand the coevolution between ECR and USP. The crystal structure of the Tribolium USP has revealed a novel type of ligand-independent USP-RXR, with no ligandbinding pocket. The ECR-USP heterodimerisation surface is symmetric and 30%larger in Mecopterida. This innovation may have been associated with a loss of homodimerisation for both USP and ECR and a reinforcement of their heterodimerisation. These results indicate that the coevolution between ECR and USP occurred, at least in part, through intra-molecular epistasis and adaptation of the heterodimerisation surface. In order to test the hypothesis that selection has shaped the USP ligand-binding domain during the evolution of insects, we analysed the evolutionary rate at different time scales. We also tested the possibility that GC-biased gene conversion played a role in the increase of nucleotide substitution rate observed for USP. Our results suggest that adaptation, drift and molecular drive shaped the structure of the nuclear receptor USP in insects. The structural evolutionary plasticity of nuclear receptors is a determinant factor for the maintenance of hormonal regulations of insect development, growth, reproduction and physiology.
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Dates et versions

hal-02593438 , version 1 (15-05-2020)

Identifiants

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François Bonneton, Arnaud Chaumot, T. Iwema, I. Billas, D. Moras, et al.. Evolution of nuclear receptors in insects. 18th International Ecdysone Workshop 2010, Jul 2010, Ceske Budejovice, Czech Republic. pp.1. ⟨hal-02593438⟩
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