Authors
L Calarco1; J Barratt1; J T Ellis1; 1 School of Life Sciences, University of Technology Sydney, Australia Discussion
Comparative studies have shown extreme differences in pathogenicity between isolates of the parasite Neospora caninum which causes abortion in cattle. These observations led to the hypothesis that intrinsic genetic differences may exist amongst N. caninum isolates that contribute to phenotypic differences. To investigate this, the present study employed a pipeline for the identification of single nucleotide polymorphisms (SNPs) in the N. caninum genome using RNA-seq data. RNA-seq data from two phenotypically different isolates of N. caninum; NC-Liverpool and NC-Nowra, were analysed using VarScan 2 to identify genetic differences between the two, using an assembled transcriptome from NC-Liverpool as a reference. PCR and DNA sequencing of SNP-containing loci were then used to extend the SNP data to additional N. caninum isolates in order to investigate patterns of genetic diversity within the species. Variant analysis identified 3130 SNPs of high confidence, and Sanger sequencing of PCR amplicons captured 56 variants, confirming 86% of these as true variants, supporting the accuracy of the variants called using the pipeline. The multilocus sequence typing results for ten isolates of N. caninum revealed a population structure reflecting two main clades that contain geographically dispersed isolates. The link to parasite virulence will be discussed.
