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Putative transcription factor binding sites and polymorphisms in the proximal promoter of the PRL-A gene in percomorphs and European sea bass (Dicentrarchus labrax)

Authors

  • Isabelle Boutet,

    1.  UMR CNRS 5554, Station Méditerranéenne de l’Environnement Littoral, Université Montpellier II, Sète, France
    2.  Present address: UMR CNRS Université Pierre et Marie Curie 7144, Adaptation et Diversité en Milieu Marin, Evolution et Génétiques des Populations Marines, Station Biologique de Roscoff, Roscoff, France
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  • Nolwenn Quéré,

    1.  UMR CNRS 5554, Station Méditerranéenne de l’Environnement Littoral, Université Montpellier II, Sète, France
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  • Frédéric Lecomte,

    1.  UMR CNRS 5554, Station Méditerranéenne de l’Environnement Littoral, Université Montpellier II, Sète, France
    2.  Present address: UMR ECOBIOP, Ecologie Comportementale et Biologie des Populations de Poissons, Pôle d’Hydrobiologie de Saint Pée sur Nivelle, INRA, Saint Pée sur Nivelle, France
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  • Jean-François Agnèse,

    1.  UMR CNRS 5554, Station Méditerranéenne de l’Environnement Littoral, Université Montpellier II, Sète, France
    2.  Institut de Recherche pour le Développement, Institut des Sciences de l’Evolution de Montpellier, Biologie Intégrative, UMR CNRS 5554, Montpellier, France
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  • Bruno Guinand

    1.  UMR CNRS 5554, Station Méditerranéenne de l’Environnement Littoral, Université Montpellier II, Sète, France
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Bruno Guinand, Station Méditerranéenne de l’Environnement Littoral, Université Montpellier II, UMR CNRS 5554, 1 Quai de la Daurade, 34200 Sète, France. E-mail: bruno.guinand@univ-montp2.fr

Abstract

There is an increasing interest in exploring how the mechanisms that regulate gene expression might generate diversity in phenotypes as a function of habitat utilisation (at both inter- and intra-specific levels). Prolactin (PRL) is the main hormone involved in adaptation to low salinity in teleosts. Several mechanisms regulating PRL-A gene expression have been described. The main mechanisms involve Pit-1 binding sites and length polymorphism of a short sequence repeat (SSR) located in the proximal promoter (PP) of the gene. Together, these processes may generate phenotypes with potentially distinct physiological responses to salinity. To gain insight into their relative roles and importance, we sequenced the PP of the PRL-A gene in the euryhaline European sea bass (Dicentrarchus labrax) and in the stenohaline sister species, Dicentrarchus punctatus. Then, we assessed the presence of both SSR and binding elements in PP among several teleost lineages, by checking available data from the literature and GenBank. The sequence of PRL-A PP was completely distinct between the percomorphs and other lineages such as salmoniform, siluriform and cypriniform, except for short stretches of nucleotides that were highly conserved across all species, also including mammals. Most of them were identified as putative cis-regulatory elements, including Pit-1, but also δEF1, c-ETS, CEBP, and GATA binding factor 2, previously unreported as regulating PRL-A transcription in teleosts, but involved in gene regulation in mammals. This result suggests that there is greater conservation of PRL-A regulatory mechanisms across vertebrate lineages than previously thought, and offers new perspectives for future studies. The presence and homology of an SSR in the PP of PRL-A gene of percomorphs was demonstrated, but no SSR polymorphisms were found amongst the two Dicentrarchus species, or within natural D. labrax populations covering the known range of natural genetic variation, including marine, brackish water and freshwater populations.

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