Abstract
BackgroundPhlebotomus papatasi is a natural vector of Leishmania major, which causes cutaneous leishmaniasis in many countries. Simple sequence repeats (SSRs), or microsatellites, are common in eukaryotic genomes and are short, repeated nucleotide sequence elements arrayed in tandem and flanked by non-repetitive regions. The enrichment methods used previously for finding new microsatellite loci in sand flies remain laborious and time consuming; in silico mining, which includes retrieval and screening of microsatellites from large amounts of sequence data from sequence data bases using microsatellite search tools can yield many new candidate markers.ResultsSimple sequence repeats (SSRs) were characterized in P. papatasi expressed sequence tags (ESTs) derived from a public database, National Center for Biotechnology Information (NCBI). A total of 42,784 sequences were mined, and 1,499 SSRs were identified with a frequency of 3.5% and an average density of 15.55 kb per SSR. Dinucleotide motifs were the most common SSRs, accounting for 67% followed by tri-, tetra-, and penta-nucleotide repeats, accounting for 31.1%, 1.5%, and 0.1%, respectively. The length of microsatellites varied from 5 to 16 repeats. Dinucleotide types; AG and CT have the highest frequency. Dinucleotide SSR-ESTs are relatively biased toward an excess of (AX)n repeats and a low GC base content. Forty primer pairs were designed based on motif lengths for further experimental validation.ConclusionThe first large-scale survey of SSRs derived from P. papatasi is presented; dinucleotide SSRs identified are more frequent than other types. EST data mining is an effective strategy to identify functional microsatellites in P. papatasi.
Highlights
Phlebotomus papatasi is a natural vector of Leishmania major, which causes cutaneous leishmaniasis in many countries
One Simple sequence repeats (SSRs) was found in every 15.55 kb of expressed sequence tags (ESTs), and the total length of the regions containing repeats was 0.079% of the total ESTs size
A total of 93 ESTs were found to have more than one SSR motifs
Summary
Phlebotomus papatasi is a natural vector of Leishmania major, which causes cutaneous leishmaniasis in many countries. Simple sequence repeats (SSRs), or microsatellites, are common in eukaryotic genomes and are short, repeated nucleotide sequence elements arrayed in tandem and flanked by non-repetitive regions. Simple sequence repeats (SSRs) or microsatellites, are common components of eukaryotic genomes and are short, repeated nucleotide sequence elements arrayed in tandem and flanked by non-repetitive regions [3,4]. SSRs often harbour high levels of polymorphism, in terms of repeat number, and have been developed into one of the most common classes of genetic markers due to their high degree of ubiquity, Parallel to the rapid increase in availability of diverse DNA sequence data, which resulted from the huge advancement of sequencing techniques, labour-intensive methods for the generation of microsatellite markers have been replaced gradually by in silico data mining of genomic and expressed sequence tag (EST) datasets [19,20,21]. SSRs are physically linked to expressed genes and represent functional markers
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