title: The plastid of Toxoplasma gondii is divided by association with the centrosomes.
abstract: Apicomplexan parasites harbor a single nonphotosynthetic plastid, the apicoplast, which is essential for parasite survival. Exploiting Toxoplasma gondii as an accessible system for cell biological analysis and molecular genetic manipulation, we have studied how these parasites ensure that the plastid and its 35-kb circular genome are faithfully segregated during cell division. Parasite organelles were labeled by recombinant expression of fluorescent proteins targeted to the plastid and the nucleus, and time-lapse video microscopy was used to image labeled organelles throughout the cell cycle. Apicoplast division is tightly associated with nuclear and cell division and is characterized by an elongated, dumbbell-shaped intermediate. The plastid genome is divided early in this process, associating with the ends of the elongated organelle. A centrin-specific antibody demonstrates that the ends of dividing apicoplast are closely linked to the centrosomes. Treatment with dinitroaniline herbicides (which disrupt microtubule organization) leads to the formation of multiple spindles and large reticulate plastids studded with centrosomes. The mitotic spindle and the pellicle of the forming daughter cells appear to generate the force required for apicoplast division in Toxoplasma gondii. These observations are discussed in the context of autonomous and FtsZ-dependent division of plastids in plants and algae.
authors.affiliation: Department of Cellular Biology and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA. striepen@cb.uga.edu
authors.forename: B
authors.initials: B
authors.lastname: Striepen
authors.forename: M J
authors.initials: MJ
authors.lastname: Crawford
authors.forename: M K
authors.initials: MK
authors.lastname: Shaw
authors.forename: L G
authors.initials: LG
authors.lastname: Tilney
authors.forename: F
authors.initials: F
authors.lastname: Seeber
authors.forename: D S
authors.initials: DS
authors.lastname: Roos
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002467:Cell Nucleus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D002502:Centrioles / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D018385:Centrosome / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D020090:Chromosome Segregation / Q000187:drug effects; D004261:DNA Replication; D016678:Genome; D008854:Microscopy, Electron; D018715:Microscopy, Video; D008954:Models, Biological; D018087:Plastids / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D014122:Toxoplasma / Q000166:cytology* / Q000187:drug effects / Q000235:genetics
chemical_list: D000814:Aniline Compounds; D018809:Proliferating Cell Nuclear Antigen; C010934:2,4-dinitroaniline