Authors

V L Hunt⁶; I J TsaiA J Reid⁸; T KikuchiA Coghlan⁸; N Holroyd⁸; J A Cotton⁸; N Randle⁵; N Brattig¹; J Wastling⁴; M Berriman⁸; M Viney³;  ¹ Bernhard Nocht Institue for Tropcial Medicine;  ² Biodiversity Research Center, Academia Sinica., Taiwan;  ³ University of Bristol;  ⁴ University of Keele; University of Liverpool;  ⁵ University of Liverpool;  ⁶ University of Liverpool; University of Bristol;  ⁷ University of Miyazaki, Japan;  ⁸ Wellcome Trust Sanger Institute

Discussion

The Strongyloides nematodes are gastrointestinal parasites of humans and other animals.  The life cycle of Strongyloides includes a parasitic female-only stage, which inhabits the small intestine of its host, and a free-living adult generation.  These adult life cycle stages are genetically identical, so that comparing parasitic and free-living stages offers an almost unique opportunity to discover the molecular adaptations required to be a successful parasitic nematode.  We have sequenced the genomes of four Strongyloides species, and two closely related species, the parasitic Parastrongyloides trichosuri and the free-living Rhabditophanes.  Using comparative analyses of the transcriptome and proteome of the parasitic and free-living stages of the Strongyloides life cycle we have identified key gene and protein families with a putative role in parasitism. Astacins, SCP/TAPS and acetylcholinestaerases are some of the most dominant gene and protein families upregulated in the parasitic adult stage.  Analysis of these three families across fourteen nematodes species has revealed that these key families have expanded coinciding with the evolution of parasitism in the Strongyloides-Parastrongyloides-Rhabditophanes nematode clade. The expansion of the astacin and SCP/TAPS families are derived from the expansion of a single gene by tandem duplication and these tandemly duplicated genes are arranged in physical clusters within the genome.