Comparative genomics of the pathogenic ciliate Ichthyophthirius multifiliis, its free-living relatives and a host species provide insights into adoption of a parasitic lifestyle and prospects for disease control

Authors

Robert S. Coyne, J Craig Venter Institute
Linda Hannick, J Craig Venter Institute
Dhanasekaran Shanmugam, University of Pennsylvania
Jessica B. Hostetler, J Craig Venter Institute
Daniel Brami, J Craig Venter Institute
Vinita S. Joardar, J Craig Venter Institute
Justin Johnson, J Craig Venter Institute
Diana Radune, J Craig Venter Institute
Irtisha Singh, J Craig Venter Institute
Jonathan H. Badger, J Craig Venter Institute
Ujjwal Kumar, University of California - San Diego
Milton Saier, University of California - San Diego
Yufeng Wang, University of Texas at San Antonio
Hong Cai, University of Texas at San Antonio
Jianying Gu, CUNY College of Staten IslandFollow
Michael W. Mather, Drexel University
Akhil B. Vaidya, Drexel University
David E. Wilkes, Indiana University at South Bend
Vidyalakshmi Rajagopalan, Indiana University South Bend
David J. Asai, Howard Hughes Medical Institute
Chad G. Pearson, University of Colorado, Denver
Robert C. Findly, University of Georgia
Harry W. Dickerson, University of Georgia
Martin Wu, University of Virginia
Cindy Martens, Ghent University
Yves Van de Peer, Ghent University
David S. Roos, University of Pennsylvania
Donna M. Cassidy-Hanley, Cornell University
Theodore G. Clark, Cornell University

Document Type

Article

Publication Date

8-11-2011

Abstract

Background

Ichthyophthirius multifiliis, commonly known as Ich, is a highly pathogenic ciliate responsible for 'white spot', a disease causing significant economic losses to the global aquaculture industry. Options for disease control are extremely limited, and Ich's obligate parasitic lifestyle makes experimental studies challenging. Unlike most well-studied protozoan parasites, Ich belongs to a phylum composed primarily of free-living members. Indeed, it is closely related to the model organism Tetrahymena thermophila. Genomic studies represent a promising strategy to reduce the impact of this disease and to understand the evolutionary transition to parasitism.

Results

We report the sequencing, assembly and annotation of the Ich macronuclear genome. Compared with its free-living relative T. thermophila, the Ich genome is reduced approximately two-fold in length and gene density and three-fold in gene content. We analyzed in detail several gene classes with diverse functions in behavior, cellular function and host immunogenicity, including protein kinases, membrane transporters, proteases, surface antigens and cytoskeletal components and regulators. We also mapped by orthology Ich's metabolic pathways in comparison with other ciliates and a potential host organism, the zebrafish Danio rerio.

Conclusions

Knowledge of the complete protein-coding and metabolic potential of Ich opens avenues for rational testing of therapeutic drugs that target functions essential to this parasite but not to its fish hosts. Also, a catalog of surface protein-encoding genes will facilitate development of more effective vaccines. The potential to use T. thermophila as a surrogate model offers promise toward controlling 'white spot' disease and understanding the adaptation to a parasitic lifestyle.

Comments

This article was originally published in Genome Biology, available at DOI: 10.1186/gb-2011-12-10-r100.

This is an open access article distributed under the terms of the Creative Commons Attribution License 2.0 (CC BY 2.0).