title: Exploiting EST databases for the development and characterization of EST-SSRs in the Pacific oyster (Crassostrea gigas).
abstract: A total of 147 microsatellite-containing expressed sequence tags (ESTs) (3.63%) were detected from 4053 ESTs of the Pacific oyster (Crassostrea gigas) in GenBank. The average density of simple sequence repeats (SSRs) was 1 per 8.25 kb of EST after redundancy elimination. Dinucleotide repeat motifs appeared to be the most abundant type. Sixteen new polymorphic EST-SSRs were developed. The number of alleles per locus varied from 3 to 12, with an average of 5.9 alleles per locus. Marker transferability was tested on 2 other Crassostrea species, and 14 loci gave successful amplifications in both species. Twenty EST-SSRs were tested on 3 families of C. gigas for examination of inheritance mode of EST-SSRs. Thirty-five tests of segregation ratios revealed 5 significant departures from expected Mendelian ratios, 4 of which confirmed Mendelian expectations when accounting for the presence of null alleles. Null alleles were detected at 3 loci (15.0%) of the 20 loci, and the frequency of null alleles at EST-SSRs was lower than that in genomic SSRs in C. gigas. The results obtained in this study suggest that C. gigas EST-SSRs will complement the currently available genomic SSR markers and may be useful for comparative mapping, marker-assisted selection, and evolutionary studies.
authors.affiliation: Department of Aquaculture, Fisheries College, Ocean University of China, Yushan Road 5, Qingdao 266003, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Yu
authors.forename: Qi
authors.initials: Q
authors.lastname: Li
mesh_terms: D000818:Animals; D030541:Databases, Genetic; D020224:Expressed Sequence Tags; D005819:Genetic Markers; D010125:Ostreidae / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic
chemical_list: D005819:Genetic Markers