A Genetic Linkage Map of the Hermaphrodite Teleost Fish Sparus aurata L.

Abstract

The gilthead sea bream (Sparus aurata L.) is a marine fish of great importance for fisheries and aquaculture. It has also a peculiar sex-determination system, being a protandrous hermaphrodite. Here we report the construction of a first-generation genetic linkage map for S. aurata, based on 204 microsatellite markers. Twenty-six linkage groups (LG) were found. The total map length was 1241.9 cM. The ratio between sex-specific map lengths was 1:1.2 (male:female). Comparison with a preliminary radiation hybrid (RH) map reveals a good concordance, as all markers located in a single LG are located in a single RH group, except for Ad-25 and CId-31. Comparison with the Tetraodon nigroviridis genome revealed a considerable number of evolutionary conserved regions (ECRs) between the two species. The mean size of ECRs was 182 bp (sequence identity 60-90%). Forty-one ECRs have a known chromosomal location in the pufferfish genome. Despite the limited number of anchoring points, significant syntenic relationships were found. The linkage map presented here provides a robust comparative framework for QTL analysis in S. aurata and is a step toward the identification of genetic loci involved both in the determination of economically important traits and in the individual timing of sex reversal. T HE gilthead sea bream (Sparus aurata L.) is a marine teleost fish that belongs to the family Sparidae. This family contains .100 species, which are divided into two large clades (groups A and B) according to the most recent molecular data (Orrell and Carpenter 2004). Sparids (porgies or sea breams) are demersal fish commonly found in temperate and tropical waters, with a maximum of diversity in the northeast Atlantic and the Mediterranean region (Bauchot and Hureau 1986), and they represent a key element of the coastal marine ecosystem. Sparids are also of great importance for fisheries and aquaculture, being excellent food fish, with high commercial value. S. aurata is the most prominent, with an average cultured production of 100 million metric tons per year. The great importance of the gilthead sea bream for marine aquaculture has fueled an increasing number of studies in many different areas such as immunology, endocrinology, bone morphology, and muscle physiology. Moreover, the genomic tool kit for S. aurata has been constantly improving, as a firstgeneration cDNA microarray was recently reported (Sarropoulou et al. 2005), a preliminary radiation hybrid (RH) map has been constructed (Senger et al. 2006), and a medium-scale expressed sequence tag (EST) sequencing project has been recently completed (A. Canario, personal communication). An improved RH map with .1000 markers (G. Kotoulas, personal communication) and an oligo array representing .10,000 unique transcripts (L. Bargelloni, personal communication) are expected by the end of 2006. Therefore, the genome of the gilthead sea bream is rapidly becoming one of the best characterized among teleost species, apart from classical models such as Brachydanio rerio (zebrafish...

A Microsatellite Genetic Map of the Turbot (Scophthalmus maximus)

“…Recombination rate has been reported to be lower in male than in female meioses in several teleost fish (Sakamoto et al 2000;Waldbieser et al 2001;Wang et al 2007). The female:male recombination rate in this study (1.6:1) is similar to the ratios observed in microsatellite-based maps in D. labrax (1.5:1; Chistiakov et al 2005) and Sparus aurata (1.2:1; Franch et al 2006), but quite different from the AFLP-based map in other flatfish species ½1:7.4, Paralichthys olivaceous (Coimbra et al 2003). In other fish species, such as Xiphophorus spp.…”

“…Very similar results were obtained using different BLAST thresholds (10 À5 -10 À10 ) for other Acantopterygii against Tetraodon genome sequences ½11%, Oreochromis niloticus (Lee et al 2005); 45%, Cottus gobio (Stemshorn et al 2005); 30%, S. aurata (Franch et al 2006); 23%, L. calcarifer (Wang et al 2007). The observed syntenic relationships, together with the sequence similarities between the turbot and Tetraodon sequences, suggest true homology of the associated regions.…”

“…The observed syntenic relationships, together with the sequence similarities between the turbot and Tetraodon sequences, suggest true homology of the associated regions. While it is interesting to speculate about the functional role of these sequences (Gaffney and Keightley 2004;Franch et al 2006), they also provide highly useful tools for linking genome information between species. Synteny among species or genera may bring the opportunity to complement initial QTL experiments with candidate gene approaches from homologous chromosomal locations identified in related model organisms (Erickson et al 2004).…”

Exploring neutral and adaptive processes in expanding populations of gilthead sea bream, Sparus aurata L., in the North-East Atlantic

“…We used a recently published linkage map for S. aurata (Franch et al, 2006;Sarropoulou et al, 2007) as a platform for the choice of markers and selected a suite of 38 markers: 23 EST-SSRs and 15 putatively neutral microsatellites (SSRs), which were multiplexed in six different reactions (Table 1, Supplementary Material). All the markers employed were from Franch et al (2006) and Vogiatzi et al (2011), apart from SauD182, SauE82 and SauI47 (Launey et al, 2003).…”

“…All the markers employed were from Franch et al (2006) and Vogiatzi et al (2011), apart from SauD182, SauE82 and SauI47 (Launey et al, 2003). PCR amplifications were carried out in a final volume of 10-12 ml containing: 20 ng of genomic DNA; 1Âreaction buffer (10 mM Tris-HCl, 1 mM MgCl 2 , 50mM KCl); 1 U of Taq DNA Polymerase and dNTPs and Mg 2+ according to conditions described in Supplementary Table S1, Supplementary Material.…”