Microsatellites in the silkworm, Bombyx mori: abundance, polymorphism, and strain characterization

Abstract

We have isolated and characterized microsatellites (simple sequence repeat (SSR) loci) from the silkworm genome. The screening of a partial genomic library by the conventional hybridization method led to the isolation of 28 microsatellites harbouring clones. The abundance of (CA)_n repeats in the silkworm genome was akin to those reported in the other organisms such as honey bee, pig, and human, but the (CT)_n repeat motif is less common compared to bumble bee and honey bee genomes. Detailed analysis of 13 diverse silkworm strains with a representative of 15 microsatellite loci revealed a number of alleles ranging from 3 to 17 with heterozygosity values of 0.66-0.90. Along with strain-specific microsatellite markers, diapause and non-diapause strain-specific alleles were also identified. The repeat length did not show any relationship with the degree of polymorphism in the present study. The co-dominant inheritance of microsatellite markers was demonstrated in F₁ offspring. A list of primer sequences that tag each locus is provided. The availability of microsatellite markers can be expected to enhance the power and resolution of genome analysis in silkworm.