(CT)n and (GT)n microsatellites: a new class of genetic markers for Salmo trutta L. (brown trout)

Abstract

Thirteen (GT ) and four (CT ), microsatellite loci (n = 10 or more and n =20 or more, respectively) have been isolated from a partial genomic library of brown trout and sequenced. On average, a (GT ) repeat sequence occurs approximately every 23 kb and a (CT ) repeat sequence every 76 kb in brown trout genome. Primers for DNA amplifications using the polymerase chain reaction (PCR) were synthesized for three single locus microsatellites. Mendelian inheritance of the observed polymorphisms was confirmed in full-sib families. Four brown trout populations (10 unrelated individuals per population) were screened for polymorphism with these three microsatellite loci. The total number of alleles detected in the four populations is five at one locus, six at the other two microsatellite loci and is three, on average, per population. Heterozygosities range from 0.18 to 0.74. The largest differences in allelic frequencies occurred between the Mediterranean and the Atlantic populations: this result is congruent with previous allozymic data. The gene-centromere distances of the three microsatellite markers were determined on gynogenetic lines: post-reduction rates range from 0.17 to 0.60. For all the three microsatellite loci, the primers designed from brown trout sequences can be used in another closely related species of salmonid, the rainbow trout (Oncorhynchus mykiss). This last aspect supports the view that microsatellite markers may have wide application in genetic studies in salmonid species and fishes in general.

Genetic differentiation in populations of the cestode Bothriocephalus acheilognathi (Cestoda, Pseudophyllidea) as revealed by eight microsatellite markers

“…Although the 8 microsatellites used in the present study exhibited PIC values slightly lower than those found for vertebrates and insects (Estoup et al 1993 ;Macaranas et al 2001), the present study demonstrated for the first time the usefulness of microsatellite markers to characterize the population structure of bothriocephalid cestodes.…”

Protein and microsatellite single locus variability in Salmo salar L. (Atlantic salmon)

“…Although two protocols have been recently adapted to analyse new allozyme loci (Verspoor & Jordan, 1994;Wilson et a!., 1995), it is apparent that a greater number of new allozyme loci will not be available for analysis in the short-term. In contrast, the total number of (dG-dT) microsatellites in the salmon haploid genome has been estimated to be 6.3 x (Slettan et a!., 1993) and other microsatellites with different repeat motifs or isolated from other related species may also be useful for salmon studies (Estoup et al, 1993, Presa et a!., 1994.…”

“…Microsatellite loci, regions of DNA containing tandem repeats of a short sequence motif, have been shown to be a rich source of of highly polymorphic genetic markers in humans and in other mammalian species and they appear to be promising markers for the detection of genetic variation in species where other methods have only revealed low variation levels (Estoup et a!., 1993;Hughes & Queller, 1993;Presa et al, 1994). In this study, all the microsatellite loci screened were polymorphic, showing between four and nine alleles per locus, with an average of 6 1.53 alleles per locus.…”

“…The PCR amplification products are then examined and sized after electrophoresis on agarose or polyacrylamide gels. In all investigated species, microsatellites have been found to be highly variable among individuals (Hamada et a!., 1982;Hearne et al, 1992;Wintero et al, 1992;Estoup et a!., 1993;Hughes & Queller, 1993). The high degree of polymorphism and random distribution in the genome make microsatellite loci promising candidates for use as genetic markers in a large scope of genetic studies such as linkage analysis, genome mapping, population structure and stock composition (Estoup et al, 1993;Hughes & Queller, 1993).…”

“…One type of repetitive element, referred to as microsatellites, corresponds to tandemly repeated DNA motifs of one to five base pairs in length evenly distributed in the genome of all investigated eukaryotic species (Hamada et a!., 1982;Weber, 1990;Wong et a!., 1990;Wintero et a!., 1992; Estoup et al, 1993;Slettan et a!., 1993).…”