Open AccessA Pseudouridine Synthase Homologue Is Critical to Cellular Differentiation in Toxoplasma gondii
Author(s) -
Matthew Anderson,
Jeremy L. Brewer,
Upinder Singh,
John C. Boothroyd
Publication year - 2009
Publication title -
eukaryotic cell
Language(s) - English
Resource type - Journals
eISSN - 1535-9778
pISSN - 1535-9786
DOI - 10.1128/ec.00329-08
Subject(s) - biology , complementation , mutant , toxoplasma gondii , insertional mutagenesis , genetics , gene , phenotype , mutagenesis , antibody
Toxoplasma gondii is a haploid protozoan parasite infecting about one in seven people in the United States. Key to the worldwide prevalence ofT. gondii is its ability to establish a lifelong, chronic infection by evading the immune system, and central to this is the developmental switch between the two asexual forms, tachyzoites and bradyzoites. A library of mutants defective in tachyzoite-to-bradyzoite differentiation (Tbd− ) was created through insertional mutagenesis. This library contains mutants that, compared to the wild type, are between 20% and 74% as efficient at stage conversion. Two mutants, TBD5 and TBD8, with disruptions in a gene encoding a putative pseudouridine synthase, PUS1, were identified. The disruption in TBD8 is in the 5′ end of thePUS1 gene and appears to produce a null allele with a 50% defect in differentiation. This is about the same switch efficiency as obtained with an engineeredpus1 deletion mutant (Δpus1 ). The insertion in TBD5 is within thePUS1 coding region, and this appears to result in a more extreme phenotype of only ∼10% switch efficiency. Complementation of TBD8 with the genomicPUS1 allele restored wild-type differentiation efficiency. Infection of mice withpus1 mutant strains results in increased mortality during the acute phase and higher cyst burdens during the chronic infection, demonstrating an aberrant differentiation phenotype in vivo due toPUS1 disruption. Our results suggest a surprising and important role for RNA modification in this biological process.