RESUMO
ß2-Microglobulin (ß2m) is related to major histocompatibility complex class I alpha chains, and forms cell-surface glycoproteins that mediate a variety of functions in immune defense. In general, ß2m has no isoforms and is not polymorphic in higher vertebrates, but polymorphisms between different alleles have been found in some fish species. In this study, full-length ß2m cDNA and genomic sequences were cloned from the miiuy croaker (Miichthys miiuy). The miiuy croaker ß2m gene shares many of the same characteristics as other fish species. Three exons and two introns were identified in the miiuy croaker ß2m gene; these genomic structural features are similar to those present in other fish. The deduced ß2m amino acid sequence exhibited 34.7-90.1% identity with mammal and teleost ß2m amino acid sequences. Sequence polymorphism analysis in six individuals identified three alleles that encoded two proteins, confirming that ß2m polymorphisms exist in this species. Phylogenetic analysis elucidated the evolutionary history of the ß2m protein among warm-blooded vertebrates and bony fish.
Assuntos
Variação Genética , Genoma , Perciformes/genética , Microglobulina beta-2/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Dados de Sequência Molecular , Filogenia , Alinhamento de Sequência , Microglobulina beta-2/químicaRESUMO
Genetic diversity and patterns of population structure of the miiuy croaker were investigated using SSR markers. A set of 10 microsatellite loci revealed 40 alleles; the number of alleles varied from 2 to 10 for each marker. A relatively high level of genetic variability was observed between miiuy croaker individuals. Genetic diversity was relatively high within populations with corresponding high average gene flow. There were genealogical branches or clusters corresponding to sampling localities according to the UPGMA tree and principal component analysis. Knowledge of the genetic diversity and population structure will be crucial for establishing appropriate fishery management stocks for this species.
Assuntos
Variação Genética , Repetições de Microssatélites , Perciformes/genética , Alelos , Animais , China , População/genéticaRESUMO
The small yellow croaker (Larimichthys polyactis) is a highly valued fish for human consumption found in the Western Pacific that was considered endangered until recently because of overfishing. We selected microsatellite markers for this species from markers developed for Miichthys miiuy, also of the family Sciaenidae. Among 43 markers polymorphic for M. miiuy, 11 were found to be polymorphic for L. polyactis. Characterization of these 11 loci was made based on 30 L. polyactis individuals collected by trawling in the Zhoushan Fishing Ground, Zhejiang Province, China. Total genomic DNA was isolated from fin clips. The number of alleles per locus ranged from 4 to 10, with a mean of 5.82, while the effective number of alleles ranged from 1.64 to 10.00, with a mean of 3.22. Observed and expected heterozygosities ranged from 0.17 to 0.72 and from 0.39 to 0.81, respectively. Significant deviation from Hardy-Weinberg equilibrium was found at four loci, after applying Bonferroni's correction. There was no significant association between any of the pairs of microsatellite loci, hence allelic variation at these loci was considered independent. These 11 polymorphic microsatellite loci will be useful for genetic diversity analysis and molecular-assisted breeding for L. polyactis.
Assuntos
Repetições de Microssatélites/genética , Perciformes/genética , Alelos , Animais , Variação Genética/genética , Heterozigoto , Polimorfismo Genético/genéticaRESUMO
The genetic diversity of Setipinna taty, which is commercially fished in the China Sea, was studied based on mitochondrial DNA control region sequences. PCR was used to amplify the control region fragment in 100 individuals of S. taty collected from Weihai (WH), Yantai (YT), Zhoushan (ZS), Xiangshan (XS), and Ninghai (NH) in China. A control region fragment of 656 bp was successfully sequenced in these 100 individuals. The A+T content of this S. taty control region was 71.7%; 172 variable sites and 62 haplotypes were found. Nucleotide diversity in the WH, YT, ZS, XS, and NH groups was 0.0228, 0.0247, 0.0441, 0.0126, and 0.0238, respectively. The haplotype diversity was 0.984, 0.911, 0.989, 0.926, and 0.979, respectively. Analysis of molecular variance showed that 97.95% of genetic variation was within populations, and only 2.05% among populations. The neighbor-joining phylogenetic tree obtained based on genetic distance showed that no significant genealogical structure exists throughout this range of S. taty. These results indicate no apparent geographical differentiation in the comparison of Yellow Sea and East China Sea populations of S. taty. Within the control region, we identified an extended termination-associated sequence domain, a central conserved sequence block domain and a conserved sequence block domain; insertions of short tandem repeat sequence segments were found at the 5' end of the control region.
Assuntos
DNA Mitocondrial/genética , Peixes/genética , Variação Genética , Animais , Sequência de Bases , Primers do DNA , Haplótipos , Dados de Sequência Molecular , Reação em Cadeia da PolimeraseRESUMO
The Venus clam, Cyclina sinensis, is one of the most important bivalves in China marine aquaculture. Using (CA)(15)-enriched genomic libraries of this species, nine novel polymorphic microsatellite loci were isolated and characterized. The mean number of observed alleles per locus was 16 (range 8-24). The observed and expected heterozygosity ranged from 0.119 to 0.872 and from 0.626 to 0.931, respectively. Three loci had significant departure from Hardy-Weinberg equilibrium and non-significant linkage disequilibrium was found among all nine loci. These highly informative microsatellite markers should be useful for population genetic analyses of C. sinensis.
Assuntos
Bivalves/genética , Repetições de Microssatélites/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Animais , Desequilíbrio de Ligação , Polimorfismo Genético/genéticaRESUMO
The Bombay duck, or bummalo (Harpadon nehereus), is a lizardfish native to the Arabian sea, but also common in the China sea. It is normally dried and salted before consumption and export. To provide molecular information on this economically important fish species, we developed and characterized microsatellite markers. Ninety positive clones from the (CA)(15)-enriched genomic library were sequenced; 62 sequences contained sufficient repeat motifs (di-, tri- and tetra-nucleotide). Twenty-eight primer pairs were designed and 21 were successfully amplified; five loci were polymorphic, but with a low number of alleles (three or four). The observed and expected heterozygosities ranged from 0.3500 to 0.8421 and from 0.5244 to 0.6244, respectively. All of the five polymorphic loci were at Hardy-Weinberg equilibrium (adjusted), while linkage disequilibrium between Hane-97 and Hane-175 (P< 0.05, adjusted P value = 0.01) was significant. The low degree of polymorphism of microsatellite markers may be due to the large size of the repeat motifs. These markers will be useful for genetic diversity analysis of H. nehereus.
Assuntos
Peixes/genética , Repetições de Microssatélites , Alelos , Animais , Variação Genética , Genoma , Desequilíbrio de LigaçãoRESUMO
Scartelaos viridis (walking goby) is a small edible fish that inhabits warm inshore environments. To provide molecular information of S. viridis, we developed and characterized microsatellite markers for this species. Using (CA)15-enriched genomic libraries of Scartelaos viridis, 44 positive clones were sequenced; 34 sequences contained multiple repeat motifs (di-, tri- and tetra-nucleotide). In all, 23 primer pairs were designed and 15 were successfully amplified. Forty-two S. viridis individuals collected from the East China Sea were used to characterize the polymorphism at each locus. Three loci (13%) were polymorphic, with three to six alleles. The observed and expected heterozygosity ranged from 0.1000 to 0.4500 and from 0.4487 to 0.7580, respectively. The polymorphism information content per locus ranged from 0.4214 to 0.7510. Three loci significantly deviated from the Hardy-Weinberg equilibrium (adjusted P value=0.017); the pairwise tests for linkage disequilibrium between Scvi-1-13 and Scvi-2-11 were significant (P<0.05, adjusted P value=0.017). The low number of polymorphic microsatellite loci may be due to the close genetic relationship of the individuals that we collected and the large size of the motifs.
Assuntos
Repetições de Microssatélites/genética , Perciformes/genética , Animais , Desequilíbrio de Ligação/genética , Reação em Cadeia da Polimerase , Polimorfismo Genético/genéticaRESUMO
Major histocompatibility complex (MHC) genes play an important role in the immune response of vertebrates. Allelic polymorphism and evolutionary mechanism of MHC genes have been investigated in many mammals, but much less is known in teleosts. We examined the polymorphism, gene duplication and balancing selection of the MHC class II DAB gene of the half-smooth tongue sole (Cynoglossus semilaevis); 23 alleles were found in this species. Gene duplication manifested as three to six distinct sequences at each domain in the same individuals. Non-synonymous substitutions occurred at a significantly higher frequency than synonymous substitutions in the PBR domain, suggesting balancing selection for maintaining polymorphisms at the MHC II DAB locus. Many positive selection sites were found to act very intensely on antigen-binding sites of MHC class II DAB gene.
Assuntos
Linguados/genética , Duplicação Gênica , Antígenos de Histocompatibilidade Classe II/genética , Polimorfismo Genético , Seleção Genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Éxons , Linguados/classificação , Linguados/imunologia , Modelos Genéticos , Dados de Sequência Molecular , Filogenia , Alinhamento de SequênciaRESUMO
Using an (AG)13 enriched genomic library of Mugil cephalus, 12 polymorphic microsatellite loci were isolated and characterized in a test population; the number of alleles ranged from 2 to 11. The observed and expected heterozygosities ranged from 0.2593 to 0.8966 and from 0.3047 to 0.8454, respectively. Two loci deviated from Hardy-Weinberg equilibrium; linkage disequilibrium among the 12 loci was non-significant. These polymorphic microsatellite loci will be useful for genetic diversity analysis and molecule-assisted breeding of the gray mullet.
Assuntos
Repetições de Microssatélites/genética , Polimorfismo Genético/genética , Smegmamorpha/genética , AnimaisRESUMO
Mytilus coruscus is one of the most important cultured species of marine shellfish in China. Using an expressed sequence tag-library and two microsatellite-enriched genomic libraries of M. coruscus, we isolated and characterized 12 polymorphic microsatellites in a test population; the number of alleles ranged from three to seven, and the observed and expected heterozygosities ranged from 0.0333 to 0.8571 and from 0.3452 to 0.8267, respectively. Four loci deviated from Hardy-Weinberg equilibrium. These polymorphic microsatellite loci can be employed in genetic diversity analysis and molecular marker-assisted breeding of M. coruscus.