Gen-Bo Xu

Eighteen novel microsatellite markers for the Chinese sea perch, Lateolabrax maculatus.

Chinese sea perch (Lateolabrax maculates) is one of the most important commercial species of mariculture in China. In this study, we constructed a repeat-enriched genomic DNA library of L. maculates. Eighteen dinucleotide microsatellite markers were characterized by genotyping 32 samples. The number of alleles ranged from three to nine, and the observed and expected heterozygosities ranged from 0.4516 to 1.0000 and from 0.4045 to 0.8676, respectively. Significant deviations from Hardy–Weinberg expectations were detected at four loci and linkage disequilibrium between two loci was significant after applying Bonferroni correction. The 18 highly polymorphic microsatellite markers should provide sufficient level of genetic diversity to investigate the population structure and evaluate the breeding strategy in L. maculates.

A new method for SNP discovery

Single nucleotide polymorphisms (SNPs) are high-density natural sequence variations in genomes. They are considered to be the major genetic source of phenotypic variability within a given species and serve as excellent genetic markers. SNPs are useful in identifying candidate genes that contribute to disease and phenotypic traits. In non-model organisms, the application of SNPs has been limited, because of the expense and technical difficulties entailed in currently available SNP isolation techniques. In the present study, we have developed a rapid and effective method to isolate SNPs throughout the genome randomly. The DNA fragments containing SNPs could be isolated efficiently from background DNA. We analyzed ten isolated DNA fragments with this method in half-smooth tongue sole (Cynoglossus semilaevis)--a newly exploited and commercially important cultured marine flatfish in China--and found that nine of the fragments contained SNPs. The findings were confirmed successfully in different individuals. The method presented here is cost-effective and applicable to essentially any organism.

Isolation and charaterization of polymorphic microsatellite loci from so-iuy mullet (Mugil soiuy Basilewsky 1855)

The first set of polymorphic microsatellite markers were developed from so-iuy mullet (Mugil soiuy Basilewsky 1855). From a (GT)n-enriched genomic library, 53 microsatellites were selected for designing microsatellite primers, of which 36 gave working primer pairs. Ten of these loci were polymorphic in a test population of 24 individuals with alleles ranging from 3 to 9, and observed and expected heterozygosities from 0.2083 to 0.9167 and from 0.2651 to 0.8812, respectively. No significant linkage disequilibrium between pairs of loci was found, but two loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. These polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate the fine-scale population structure and evaluate the breeding strategy in Mullet.

Isolation and characterization of 10 polymorphic microsatellite loci from small yellow croaker (Pseudosciaena polyactis)

Small yellow croaker (Pseudosciaena polyactis) is an economically important marine fish species. About 43 microsatellite loci were isolated from two enriched genomic library of Pseudosciaena polyactis. Ten of these loci were polymorphic in a test population with alleles per locus ranging from two to six, and observed and expected heterozygosities per locus from 0.3750 to 0.8750 and from 0.3112 to 0.8121, respectively. No loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction and no significant linkage disequilibrium was found between pairs of loci. These polymorphic microsatellite loci would be useful for investigating genetic diversity of Pseudosciaena polyactis.

New polymorphic microsatellite markers for bluefin leatherjacket (Navodon septentrionalis Gunther, 1877)

A microsatellite-enriched genomic DNA library of Navodon septentrionalis was generated and screened by sequencing. Ten dinucleotide microsatellite loci were characterized by genotyping 24 samples. The observed number of alleles ranged from two to seven with an average of 4.40, while the effective number of alleles ranged from 1.49 to 5.70 with an average of 3.31. The observed and expected heterozygosities ranged from 0.2917 to 0.9167 and from 0.3369 to 0.8422, respectively. No significant linkage disequilibrium between pairs of loci was found, but one loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. These polymorphic microsatellite loci would be useful for investigating genetic population structure and molecule-assisted breeding for N. septentrionalis.

Isolation and charaterization of 12 dinucleotide microsatellite loci from Belenger’s jewfish ( Johnius belengerii Cuvier 1830)

We describe the first isolation of 12 polymorphic microsatellite markers from Belenger’s jewfish (Johnius belengnerii Cuvier 1830). From a (GT)n-enriched genomic library, 54 microsatellites were selected for designing microsatellite primers, of which 36 gave working primer pairs. 12 of these loci were polymorphic in a test population of 21 individuals with alleles ranging from 3 to 18, and expected and observed heterozygosities from 0.5772 to 0.9449 and from 0.4286 to 0.9231, respectively. No significant linkage disequilibrium between pairs of loci was found, however, loci Jobe24 significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. These polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate population structure in Belenger’s jewfish.

Isolation and characterization of 30 novel polymorphic microsatellite loci from Japanese halfbeak, Hyporhamphus sajori (Temminck et Schlegel, 1846)

The construction of genetic linkage map and evaluation of population genetic diversity both require large numbers of polymorphic molecular markers. In the study, 60 microsatellite loci were isolated from a dinucleotide-enriched genomic library of Japanese halfbeak (Hyporhamphus sajori). And 30 polymorphic microsatellite loci were found to be polymorphic between 2 and 11 alleles. The number of observed, expected heterozygosity and polymorphism information content per locus in 24 individuals ranged from 0.1667 to 1.000, 0.1828 to 0.9220, 0.1828 to 0.8945, respectively. Three loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction analysis and there was no significant linkage disequilibrium found between pairs of loci. As a result, 30 microsatellite loci probably should provide sufficient level of genetic diversity to investigate the fine-scale population structure, stock management and enhancement, genetic linkage map construction and molecular marker-assisted breeding in H. sajori.

Ten polymorphic microsatellite loci for the Atlantic halibut (Hippoglossus hippoglossus) and cross-species application in related species

In the present study, 10 polymorphic microsatellite DNA loci from Atlantic halibut (Hippoglossus hippoglossus) were isolated and characterized. The number of alleles for these loci ranged from 2 to 4 in tested 24 individuals. Observed and expected heterozygosities per locus varied from 0.21 to 0.70 and from 0.31 to 0.65, respectively. Most of these 10 microsatellite loci were successfully amplified and showed polymorphic in five related species. These loci will be useful for the assessment of genetic diversity and population structure of Atlantic halibut.

Isolation and characterization of polymorphic microsatellite loci from bluefin leatherjacket ( Navodon septentrionalis Gunther, 1877)

The first set of 18 polymorphic microsatellite markers were developed from bluefin leatherjacket (Navodon septentrionalis Gunther, 1877). From a (GT)n-enriched genomic library, we got 121 microsatellites, of which 60 were randomly selected for designing microsatellite primers. Eighteen of these loci were polymorphic in a test population of 32 individuals with alleles ranging from 2 to 9, and expected and observed heterozygosities from 0.1463 to 0.8517 and from 0.1562 to 1.0000, respectively. No significant linkage disequilibrium between pairs of loci was found, but three loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction. These polymorphic microsatellite loci should provide sufficient level of genetic diversity to investigate population structure in bluefin leatherjacket.

New polymorphic microsatellite markers for the summer flounder, Paralichthys dentatus

Given the ecological and commercial importance of the summer flounder (Paralichthys dentatus), there is a surprising paucity of information on the molecular genetics of this species. Some studies published to date are concentrated on the reproduction biology. To address this shortcoming, a microsatellite-enriched genomic DNA library of P. dentatus was generated and screened by sequencing. Twelve dinucleotide microsatellite loci were characterized by genotyping 24 samples. The observed number of alleles ranged from three to thirteen with an average of 8.25, while the effective number of alleles ranged from 2.21 to 8.28 with an average of 5.06. The observed and expected heterozygosities ranged from 0.0833 to 0.9583 and from 0.5594 to 0.8980, respectively. Significant deviations from Hardy–Weinberg expectations were detected at three loci and linkage disequilibrium between two loci was significant after applying Bonferroni correction. In cross-species amplification, three species showed at least two polymorphic loci. The 12 highly polymorphic microsatellite markers represent a powerful molecular tool, which will allow for detailed population genetic analyses on this important marine fish.