Selection at a single locus leads to widespread expansion of toxoplasma gondii lineages that are virulent in mice

Khan, A., Taylor, S., Ajioka, J.W., Rosenthal, B.M. and Sibley, L.D. (2009) Selection at a single locus leads to widespread expansion of toxoplasma gondii lineages that are virulent in mice. PLoS Genetics, 5(3), e1000404. (doi: 10.1371/journal.pgen.1000404)

Abstract

The determinants of virulence are rarely defined for eukaryotic parasites such as T. gondii, a widespread parasite of mammals that also infects humans, sometimes with serious consequences. Recent laboratory studies have established that variation in a single secreted protein, a serine/threonine kinase known as ROPO18, controls whether or not mice survive infection. Here, we establish the extent and nature of variation in ROP18among a collection of parasite strains from geographically diverse regions. Compared to other genes, ROP18 showed extremely high levels of diversification and changes in expression level, which correlated with severity of infection in mice. Comparison with an out-group demonstrated that changes in the upstream region that regulates expression of ROP18 led to an historical increase in the expression and exposed the protein to diversifying selective pressure. Surprisingly, only three atypically distinct protein variants exist despite marked genetic divergence elsewhere in the genome. These three forms of ROP18 are likely adaptations for different niches in nature, and they confer markedly different virulence to mice. The widespread distribution of a single mouse-virulent allele among geographically and genetically disparate parasites may have consequences for transmission and disease in other hosts, including humans.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Taylor, Dr Sonya
• Authors: Khan, A., Taylor, S., Ajioka, J.W., Rosenthal, B.M., and Sibley, L.D.
• College/School: College of Medical Veterinary and Life Sciences; College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Journal Name: PLoS Genetics
• Publisher: Public Library of Science
• ISSN: 1553-7390
• ISSN (Online): 1553-7404
• Published Online: 06 March 2009
• Copyright Holders: Copyright © 2009 The Authors.
• First Published: First published in PLoS Genetics 2009 5(3): e1000404
• Publisher Policy: Open Access article distributed under the terms of the Creative Commons Attribution License