COMPOSITE GENOME MAP AND RECOMBINATION PARAMETERS DERIVED FROM THREE ARCHETYPAL LINEAGES OF TOXOPLASMA GONDII

Authors: KHAN, ASIS - ST.LOUIS, MO; TAYLOR, SONYA - ST.LOUIS, MO; SU, CHUNLEI - ST.LOUIS, MO; MACKEY, AARON - U PENN, PA; BOYLE, JON - STANFORD, CA; COLE, ROBERT - ST.LOUIS, MO; GLOVER, DARIUS - ST.LOUIS, MO; TANG, KELIANG - ST.LOUIS, MO; PAULSEN, IAN - ROCKVILLE, MD; Dubey, Jitender

Submitted to: Nucleic Acids Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2005
Publication Date: 7/2/2005
Citation: Khan, A., Taylor, S., Su, C., Mackey, A.J., Boyle, J., Cole, R., Glover, D., Tang, K., Paulsen, I.T., Dubey, J.P. 2005. Composite genome map and recombination parameters derived from three archetypal lineages of Toxoplasma gondii. Nucleic Acids Research. 33:2980-2992.

Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating undercooked meat from infected animals and food and water contaminated with oocysts. Scientists at the Beltsville Agricultural Research Center and Washington University School of Medicine report the genetic map of T. gondii. The results will be of interest to biologists, parasitologists, and veterinarians.

Technical Abstract: Toxoplasma gondii is a highly successful protozoan parasite in the phylum Apicomplexa, which contains numerous animal and human pathogens. T. gondii is amenable to cellular, biochemical, molecular and genetic studies, making it a model for the biology of this important group of parasites. To facilitate forward genetic analysis we have developed a high-resolution genetic linkage map for T. gondii. The genetic map was used to assemble the scaffolds from a 10X shotgun whole genome sequence, thus defining 14 chromosomes with markers spaced at ~ 300 kb intervals across the genome. Fourteen chromosomes were identified comprising a total genetic size of ~592 cM and an average map unit of ~104 kb / cM. Analysis of the genetic parameters is T. gondii revealed a high frequency of closely adjacent, apparent double crossover events that may represent gene conversions. In addition, we detected large regions of genetic homogeneity among the archetypal clonal lineages, reflecting the relatively few genetic outbreeding events that have occurred since their recent origin. Despite these unusual features, linkage analysis proved to be effective in mapping the loci determining several drug resistances. The resulting genome map provides a framework for analysis of complex traits such as virulence and transmission, and for comparative population genetic studies.