title: Genetic analysis of tachyzoite to bradyzoite differentiation mutants in Toxoplasma gondii reveals a hierarchy of gene induction.
abstract: Developmental switching in Toxoplasma gondii, from the virulent tachyzoite to the relatively quiescent bradyzoite stage, is responsible for disease propagation and reactivation. We have generated tachyzoite to bradyzoite differentiation (Tbd-) mutants in T. gondii and used these in combination with a cDNA microarray to identify developmental pathways in bradyzoite formation. Four independently generated Tbd- mutants were analysed and had defects in bradyzoite development in response to multiple bradyzoite-inducing conditions, a stable phenotype after in vivo passages and a markedly reduced brain cyst burden in a murine model of chronic infection. Transcriptional profiles of mutant and wild-type parasites, growing under bradyzoite conditions, revealed a hierarchy of developmentally regulated genes, including many bradyzoite-induced genes whose transcripts were reduced in all mutants. A set of non-developmentally regulated genes whose transcripts were less abundant in Tbd- mutants were also identified. These may represent genes that mediate downstream effects and/or whose expression is dependent on the same transcription factors as the bradyzoite-induced set. Using these data, we have generated a model of transcription regulation during bradyzoite development in T. gondii. Our approach shows the utility of this system as a model to study developmental biology in single-celled eukaryotes including protozoa and fungi.
authors: D305 Fairchild Building, Department of Microbiology and Immunology, Stanford University School of Medicine, CA 94305-5124, USA.
authors: Upinder
authors: U
authors: Singh
authors: Jeremy L
authors: JL
authors: Brewer
authors: John C
authors: JC
authors: Boothroyd
mesh_terms: D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology; D053626:Atovaquone; D002454:Cell Differentiation / Q000235:genetics; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D017125:Genes, Protozoan; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D016296:Mutagenesis; D009285:Naphthoquinones / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D015800:Protozoan Proteins / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D012641:Selection, Genetic; D014122:Toxoplasma / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D014124:Toxoplasmosis, Animal / Q000469:parasitology; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D000981:Antiprotozoal Agents; D008164:Luminescent Proteins; D009285:Naphthoquinones; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D053626:Atovaquone