Common inheritance of chromosome Ia associated with clonal expansion of Toxoplasma gondii

Asis Khan, Ulrike Böhme, Krystyna A. Kelly, Ellen Adlem, Karen Brooks, Mark Simmonds, Karen Mungall, Michael A. Quail, Claire Arrowsmith, Tracey Chillingworth, Carol Churcher, David Harris, Matthew Collins, Nigel Fosker, Audrey Fraser, Zahra Hance, Kay Jagels, Sharon Moule, Lee Murphy, Susan O'NeilMarie Adele Rajandream, David Saunders, Kathy Seeger, Sally Whitehead, Thomas Mayr, Xuenan Xuan, Junichi Watanabe, Yutaka Suzuki, Hiroyuki Wakaguri, Sumio Sugano, Chihiro Sugimoto, Ian Paulsen, Aaron J. Mackey, David S. Roos, Neil Hall, Matthew Berriman, Bart Barrell, L. David Sibley, James W. Ajioka*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)

Abstract

Toxoplasma gondii is a globally distributed protozoan parasite that can infect virtually all warm-blooded animals and humans. Despite the existence of a sexual phase in the life cycle, T. gondii has an unusual population structure dominated by three clonal lineages that predominate in North America and Europe, (Types I, II, and III). These lineages were founded by common ancestors ∼10,000 yr ago. The recent origin and widespread distribution of the clonal lineages is attributed to the circumvention of the sexual cycle by a new mode of transmission - asexual transmission between intermediate hosts. Asexual transmission appears to be multigenic and although the specific genes mediating this trait are unknown, it is predicted that all members of the clonal lineages should share the same alleles. Genetic mapping studies suggested that chromosome Ia was unusually monomorphic compared with the rest of the genome. To investigate this further, we sequenced chromosome Ia and chromosome Ib in the Type I strain, RH, and the Type II strain, ME49. Comparative genome analyses of the two chromosomal sequences revealed that the same copy of chromosome Ia was inherited in each lineage, whereas chromosome Ib maintained the same high frequency of between-strain polymorphism as the rest of the genome. Sampling of chromosome Ia sequence in seven additional representative strains from the three clonal lineages supports a monomorphic inheritance, which is unique within the genome. Taken together, our observations implicate a specific combination of alleles on chromosome Ia in the recent origin and widespread success of the clonal lineages of T. gondii.

Original languageEnglish
Pages (from-to)1119-1125
Number of pages7
JournalGenome Research
Volume16
Issue number9
DOIs
Publication statusPublished - 2006
Externally publishedYes

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