The genome of Eimeria falciformis--reduction and specialization in a single host apicomplexan parasite.

Emanuel Heitlinger,Christoph Dieterich,Richard Lucius,Simone Spork

doi:10.1186/1471-2164-15-696

Emanuel Heitlinger, Christoph Dieterich + Show 2 more

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https://doi.org/10.1186/1471-2164-15-696

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Abstract

BackgroundThe phylum Apicomplexa comprises important unicellular human parasites such as Toxoplasma and Plasmodium. Eimeria is the largest and most diverse genus of apicomplexan parasites and some species of the genus are the causative agent of coccidiosis, a disease economically devastating in poultry. We report a complete genome sequence of the mouse parasite Eimeria falciformis. We assembled and annotated the genome sequence to study host-parasite interactions in this understudied genus in a model organism host.ResultsThe genome of E. falciformis is 44 Mb in size and contains 5,879 predicted protein coding genes. Comparative analysis of E. falciformis with Toxoplasma gondii shows an emergence and diversification of gene families associated with motility and invasion mainly at the level of the Coccidia. Many rhoptry kinases, among them important virulence factors in T. gondii, are absent from the E. falciformis genome. Surface antigens are divergent between Eimeria species. Comparisons with T. gondii showed differences between genes involved in metabolism, N-glycan and GPI-anchor synthesis. E. falciformis possesses a reduced set of transmembrane transporters and we suggest an altered mode of iron uptake in the genus Eimeria.ConclusionsReduced diversity of genes required for host-parasite interaction and transmembrane transport allow hypotheses on host adaptation and specialization of a single host parasite. The E. falciformis genome sequence sheds light on the evolution of the Coccidia and helps to identify determinants of host-parasite interaction critical for drug and vaccine development.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-696) contains supplementary material, which is available to authorized users.

Highlights

The phylum Apicomplexa comprises important unicellular human parasites such as Toxoplasma and Plasmodium
The five longest contigs of the assembly cover a combined length of 4.6 Mb and could very well represent some of the typically 14 chromosomes found in Eimeria species and other Coccidia [21]
With this size the genome of E. falciformis is smaller than those of other Eimeria species [18]. It ranges between the size of the strongly reduced genomes of Cryptosporidium parvum and the relatively large one of T. gondii (Table 1)

Summary

Introduction

The phylum Apicomplexa comprises important unicellular human parasites such as Toxoplasma and Plasmodium. Eimeria is the largest and most diverse genus of apicomplexan parasites and some species of the genus are the causative agent of coccidiosis, a disease economically devastating in poultry. We report a complete genome sequence of the mouse parasite Eimeria falciformis. We assembled and annotated the genome sequence to study host-parasite interactions in this understudied genus in a model organism host. The taxon Eimeria is the largest genus of the phylum Apicomplexa with more than 1,800 species [1]. The Apicomplexa are obligate intracellular parasites and the phylum contains many well-known pathogens of humans and livestock. Plasmodium species causing malaria can be regarded as the most threatening eukaryotes to human [2]. The family comprises human pathogenic parasites like Isospora belli

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