A preliminary study on microsatellite markers screening from EST sequences of Litopenaeus vannamei

EST-SSR marker development by screening and mining the SSR repeats in the EST database of Litopenaeus vannamei,161 075 EST sequences were downloaded from EST sequences in the database of GenBank.EST sequences were analyzed and the SSR was screened with SSIRT(http:∥www.gramene.org/db/markers.ssrtoo).As a result,12 600(7.8%)SSRs were identified from the EST resources,among which there were 10 104(80.2%)dinucleotide,2 036(16.1%)trinucleotide,336(2.7%)tetranucleotide,35(0.3%)pentanucleotide and 89(0.7%)hexanucleode SSRs.Among the dinucleotide sequences,AG/CT repeat motif accounted for 4 820(47.8%),3 584(35.4%)AC/GT repeat motif,AT/TA,CG/GC repeat motif was 1 673(6.6%),27(0.2%)respectively.77 pairs of primers were designed with Primer Premier 5.0.Fifty four primer pairs obtained expected product,with the success rate of 70.1%.And 28 of them showed polymorphism among 10 individuals,polymorphism rate was 51.9%.Number of alleles ranged from 2 to 5,and PCR product size was 140-600 bp.This implies that the polymorphism EST-SSR developed from NCBI could work in genetic mapping,gene clone and gene functional research.