The population genetic structure of sea bass (Dicentrarchus labrax) along a transect from the Atlantic Ocean (AO) to the Eastern Mediterranean (EM) Sea differs from that of most other marine taxa in this area. Three populations (AO, Western Mediterranean [WM], EM) are recognized today, which were originally two allopatric populations. How two ancestral genetic units have evolved into three distinct units has not been addressed yet. Therefore, to investigate mechanisms that lead to the emergence of the central WM population, its current status, and its connectivity with the two parental populations, we applied 20 nuclear loci that were either gene associated or gene independent. Results confirmed the existence of three distinct gene pools, with higher differentiation at two transitional areas, the Almeria-Oran Front (AOF) and of the Siculo-Tunisian Strait (STS), than within any population. Significant linkage disequilibrium and heterozygote excess indicated that the STS is probably another tension zone, as already described for the AOF. Neutrality tests fail to reveal marker loci that could be driven by selection within or among metapopulations, except for locus DLA0068. Collectively, results support that the central WM population arose by trapping two tensions zones at distinct geographic locations of limited connectivity. Population assignment further revealed that WM individuals were more introgressed than individuals from the other two metapopulations. This suggests that this population might result from hybrid swarming, and was or is still seeded by genes received through the filter of each tension zone.

-The completion of genomic sequences of physiologically important genes frequently reveals non-coding genetic elements such as tandem repeats (micro-and minisatellites) that are often more polymorphic than nearby coding sequences. We obtained the complete genomic sequences of three hormone genes in sea bass Dicentrarchus labrax: growth hormone (dlGH), somatolactin (dlSL) and insulin-like growth factor-1 (dlIGF-1), including 5 -and 3 -untranslated regions. Mini-and microsatellites were discovered in both flanking and intron regions. Some were partially conserved across Perciformes. To assess the usefulness and relevance of these gene-associated markers for understanding population structure, an investigation was made on genetic diversity and differentiation at four of them in (i) five wild populations from the North Sea, the Bay of Biscay and the Western Mediterranean, and (ii) two samples of hatchery-bred individuals from a freshwater-acclimation experiment. Gene and allelic diversities were lower in cultured individuals than in wild ones. Significant genetic differentiation was demonstrated between Bay of Biscay + North Sea and Mediterranean populations (F st > 0.06, p < 0.001), primarily due to dlGH-associated markers. Significant genetic differentiation was also detected among the Atlantic and North Sea samples, but restricted to the locus associated with dlSL. Significant genetic differentiation was also found among experimental individuals before and after a salinity challenge (F st ≈ 0.05, p < 0.001), but was due to dlSL and dlIGF-1 loci. Gene-associated markers proved to be more efficient than formerly used anonymous microsatellite markers in providing a clear picture of genetic differentiation.Key words: Growth hormone / Somatolactin / Insulin-like growth factor-1 / Non-coding regions / European sea bass / Microsatellites / Minisatellites Résumé -Connaître les séquences génomiques de gènes d'importance physiologique permet de déceler des élé-ments génétiques non-codants tels que des répétitions en tandem (micro -et minisatellites), souvent porteurs de davantage de polymorphismes que les séquences codantes voisines. Des séquences génomiques complètes ainsi que celles de leurs régions flanquantes en 5 et 3 sont établies pour trois gènes codants pour des hormones chez le bar, Dicentrarchus labrax : l'hormone de croissance (dlGH), la somatolactine (dlSL) et le facteur de croissance apparenté à l'insuline (dlIGF-1). Ainsi, un mini-et des microsatellites partiellement conservés chez les Perciformes ont été trouvés. Pour évaluer la pertinence de ces marqueurs pour des études de structure génétique des populations, leur diversité et leur différenciation génétiques sont examinées chez (i) cinq populations sauvages de la mer du Nord, du golfe de Gascogne et de la Méditerranée occidentale, ainsi que dans ( Resour. 23, 285-296 (2010) pour le locus associé à dlSL. Enfin, pour les marqueurs associés à dlSL et dlIGF-1, une différenciation génétique significative est mise en évidence entre individus expérim...

International audienceWe describe a simple protocol to reduce the number of cloning reactions of nuclear DNA sequences in population genetic studies of diploid organisms. Cloning is a necessary step to obtain correct haplotypes in such organisms, and, while traditional methods are efficient at cloning together many genes of a single individual, population geneticists rather need to clone the same locus in many individuals. Our method consists of marking individual sequences during the polymerase chain reaction (PCR) using 5'-tailed primers with small polynucleotide tags. PCR products are mixed together before the cloning reaction and clones are sequenced with universal plasmid primers. The individual from which a sequence comes from is identified by the tag sequences upstream of each initial primer. We called our protocol mark-recapture (MR) cloning. We present results from 57 experiments of MR cloning conducted in four distinct laboratories using nuclear loci of various lengths in different invertebrate species. Rate of capture (proportion of individuals for which one or more sequences were retrieved) and multiple capture (proportion of individuals for which two or more sequences were retrieved) empirically obtained are described. We estimated that MR cloning allowed reducing costs by up to 70% when compared to conventional individual-based cloning. However, we recommend to adjust the mark:recapture ratio in order to obtain multiple sequences from the same individual and circumvent inherent technical artefacts of PCR, cloning and sequencing. We argue that MR cloning is a valid and reliable high-throughput method, providing the number of sequences exceeds the number of individuals initially amplified

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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 dEF1, 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.

Abstract. In a geopolitical very complex context as the Gaza Strip it has to be dealt with an enhancement of an archaeological site. This site is the monastery of St. Hilarion. To enable a cultural appropriation of a place with several identified phases of occupation must undertake extensive archaeological excavation. Excavate in this geographical area is to implement emergency excavations, so the aim of such a project can be questioned for each mission. Real estate pressure is also a motivating setting the documentation because the large population density does not allow systematic studies of underground before construction projects. This is also during the construction of a road that the site was discovered. Site dimensions are 150 m by 80 m. It is located on a sand dune, 300 m from the sea. To implement the survey, four different levels of detail have been defined for terrestrial photogrammetry. The first level elements are similar to objects, capitals, fragment of columns, tiles for example. Modeling of small objects requires the acquisition of very dense point clouds (density: 1 point / 1 mm on average). The object must then be a maximum area of the sensor of the camera, while retaining in the field of view a reference pattern for the scaling of the point cloud generated. The pictures are taken at a short distance from the object, using the images at full resolution. The main obstacle to the modeling of objects is the presence of noise partly due to the studied materials (sand, smooth rock), which do not favor the detection of points of interest quality. Pretreatments of the cloud will be achieved meticulously since the ouster of points on a surface of a small object results in the formation of a hole with a lack of information, useful to resulting mesh. Level 2 focuses on the stratigraphic units such as mosaics. The monastery of St. Hilarion identifies thirteen floors of which has been documented years ago by silver photographs, scanned later. Modeling of pavements is to obtain a three-dimensional model of the mosaic in particular to analyze the subsidence, which it may be subjected. The dense point cloud can go beyond by including the geometric shapes of the pavement. The calculation mesh using high-density point cloud colorization allows cloud sufficient to final rendering. Levels 3 and 4 will allow the survey and representation of loci and sectors. Their modeling can be done by colored mesh or textured by a generic pattern but also by geometric primitives. This method requires the segmentation simple geometrical elements and creates a surface geometry by analysis of the sample points. Statistical tools allow the extraction plans meet the requirements of the operator can monitor quantitatively the quality of the final rendering. Each level has constraints on the accuracy of survey and types of representation especially from the point clouds, which are detailed in the complete article.

International audienceLarge-scale mortality events have been observed in Pacific oyster Crassostrea gigas on the west coast of France since the early 1980s, particularly during summer. In order to understand the causes of this mortality, two generations of oysters from single-pair matings were studied in three sites on the French Atlantic coast (Baie-des-Veys, Auray and Ronce-les-Bains). The present paper examines the role of two candidate genes in the susceptibility of oysters to summer mortality, and the selective pressure exerted by such mortality on their polymorphism. Glutamine synthetase (amino-acid metabolism) and delta-9 desaturase (lipid metabolism) genes were studied in the successive generations, using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP). Observed and expected genotypic frequencies were compared. Three different alleles were detected for the glutamine synthetase gene and two for delta-9 desaturase. Allele C of glutamine synthetase seemed to be counter-selected in some second generation families. Allele B of delta-9 desaturase gene was potentially counter-selected at Auray in the families showing higher mortality, and strong selection against BB homozygotes was observed. These observations led us to conclude that any selective effect of summer mortality on allele C of glutamine synthetase gene or allele B of delta-9 desaturase gene could be mediated either directly or via linkage to other loci involved in physiological pathways affecting susceptibility

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