Screening potential SSR markers of the anadromous fish Coilia nasus by de novo transcriptome analysis using Illumina...

RNA-Seq technology has been widely applied to transcriptomics, genomics, molecular marker development, and functional gene studies. In the genome, microsatellites are simple sequence repeats (SSR) with a high degree of polymorphism that are used as DNA markers in many molecular genetic studies. Using traditional methods such as magnetic bead enrichment, only a few microsatellite markers have been isolated. Coilia nasus is an anadromous, small-to-moderately sized fish species that is famous as an important fishery resource. Here, we have identified a large number of microsatellites from the fish brains by using Illumina sequencing. About 20 million Illumina reads were assembled into 148,845 unigenes. A total of 13,038 SSR motifs were identified via analysis of 3,958,293,117 (3.96 Gb) nucleotides to produce a comprehensive transcript dataset for the C. nasus brain, including mono-, di-, tri-, tetra-, and penta-repeat motifs. The most abundant type of repeat motif was di-nucleotide (42.97%), followed by mono-nucleotide (38.86%), tri-nucleotide (16.21%), tetra-nucleotide (1.83%), and penta-nucleotide (0.05%) repeat units, which is similar to the results obtained in studies in other species. These data provide a base of sequence information to improve molecular-assisted markers to study C. nasus genetic diversity.