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Variation in gene expression along a salinity gradient in wild populations of the euryhaline black-chinned tilapia Sarotherodon melanotheron

Authors

  • M. Tine,

    Corresponding author
    1. Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, D-14195 Berlin, Germany
    2. Université Montpellier II, CNRS-UMR 5554 (Institut des Sciences de l’Evolution de Montpellier), Station Méditerranéenne de l’Environnement Littoral, Sète 34200, France
      Tel.: +49 30 8413 1556; email: tine@molgen.mpg.de; mbtine@hotmail.fr
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  • B. Guinand,

    1. Université Montpellier II, CNRS-UMR 5554 (Institut des Sciences de l’Evolution de Montpellier), Station Méditerranéenne de l’Environnement Littoral, Sète 34200, France
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  • J.-D. Durand

    1. IRD, UMR 5119 ECOSYM, route des hydrocarbures BP 1386 18524 Dakar, Senegal
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Tel.: +49 30 8413 1556; email: tine@molgen.mpg.de; mbtine@hotmail.fr

Abstract

This study evaluated variation in expression of 11 genes within and among six wild populations of the black-chinned tilapia Sarotherodon melanotheron distributed along a salinity gradient from 0 to 100. Previous laboratory studies had shown that expression of these genes was sensitive to water salinity; the current study confirmed that a number of them also varied in expression in wild populations along the salinity gradient. Principal component analysis (PCA) first distinguished two, not mutually exclusive, sets of genes: trade-off genes that were highly expressed at one or other extreme of the salinity gradient and stress genes that were up-regulated at the two salinity extremes (i.e. a U-shaped expression pattern). The PCA clearly partitioned the populations into three groups based on their gene expression patterns and their position along the salinity gradient: a freshwater (GL; 0) population, four brackish and seawater (GB, HB, SM, SF; ranging from 20 to 50) populations and a hypersaline (SK, 100) population. Individual variation in gene expression was significantly greater within the populations at the extreme compared to intermediate salinities. These results reveal phenotypically plastic regulation of gene expression in S. melanotheron, and greater osmoregulatory and plasticity costs at extreme salinities, where fitness-related traits are known to be altered.

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