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  • 1
    Online Resource
    Online Resource
    Just one cross appears capable of dramatically altering the population biology of a eukaryotic pathogen like Toxoplasma gondii
    Proceedings of the National Academy of Sciences ; 2006
    In:  Proceedings of the National Academy of Sciences Vol. 103, No. 27 ( 2006-07-05), p. 10514-10519
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 103, No. 27 ( 2006-07-05), p. 10514-10519
    Abstract: Toxoplasma gondii , an obligate intracellular protozoan of the phylum Apicomplexa, is estimated to infect over a billion people worldwide as well as a great many other mammalian and avian hosts. Despite this ubiquity, the vast majority of human infections in Europe and North America are thought to be due to only three genotypes. Using a genome-wide analysis of single-nucleotide polymorphisms, we have constructed a genealogy for these three lines. The data indicate that types I and III are second- and first-generation offspring, respectively, of a cross between a type II strain and one of two ancestral strains. An extant T. gondii strain (P89) appears to be the modern descendant of the non-type II parent of type III, making the full genealogy of the type III clonotype known. The simplicity of this family tree demonstrates that even a single cross can lead to the emergence and dominance of a new clonal genotype that completely alters the population biology of a sexual pathogen.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0510319103
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2006
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  • 2
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    Online Resource
    Dissecting Apicoplast Targeting in the Malaria Parasite Plasmodium falciparum
    American Association for the Advancement of Science (AAAS) ; 2003
    In:  Science Vol. 299, No. 5607 ( 2003-01-31), p. 705-708
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 299, No. 5607 ( 2003-01-31), p. 705-708
    Abstract: Transit peptides mediate protein targeting into plastids and are only poorly understood. We extracted amino acid features from transit peptides that target proteins to the relict plastid (apicoplast) of malaria parasites. Based on these amino acid characteristics, we identified 466 putative apicoplast proteins in the Plasmodium falciparum genome. Altering the specific charge characteristics in a model transit peptide by site-directed mutagenesis severely disrupted organellar targeting in vivo. Similarly, putative Hsp70 (DnaK) binding sites present in the transit peptide proved to be important for correct targeting.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1078599
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2003
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
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  • 3
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    Nuclear-encoded proteins target to the plastid in Toxoplasma gondii and Plasmodium falciparum
    Proceedings of the National Academy of Sciences ; 1998
    In:  Proceedings of the National Academy of Sciences Vol. 95, No. 21 ( 1998-10-13), p. 12352-12357
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 95, No. 21 ( 1998-10-13), p. 12352-12357
    Abstract: A vestigial, nonphotosynthetic plastid has been identified recently in protozoan parasites of the phylum Apicomplexa. The apicomplexan plastid, or “apicoplast,” is indispensable, but the complete sequence of both the Plasmodium falciparum and Toxoplasma gondii apicoplast genomes has offered no clue as to what essential metabolic function(s) this organelle might perform in parasites. To investigate possible functions of the apicoplast, we sought to identify nuclear-encoded genes whose products are targeted to the apicoplast in Plasmodium and Toxoplasma . We describe here nuclear genes encoding ribosomal proteins S9 and L28 and the fatty acid biosynthetic enzymes acyl carrier protein (ACP), β-ketoacyl-ACP synthase III (FabH), and β-hydroxyacyl-ACP dehydratase (FabZ). These genes show high similarity to plastid homologues, and immunolocalization of S9 and ACP verifies that the proteins accumulate in the plastid. All the putatively apicoplast-targeted proteins bear N-terminal presequences consistent with plastid targeting, and the ACP presequence is shown to be sufficient to target a recombinant green fluorescent protein reporter to the apicoplast in transgenic T. gondii . Localization of ACP, and very probably FabH and FabZ, in the apicoplast implicates fatty acid biosynthesis as a likely function of the apicoplast. Moreover, inhibition of P. falciparum growth by thiolactomycin, an inhibitor of FabH, indicates a vital role for apicoplast fatty acid biosynthesis. Because the fatty acid biosynthesis genes identified here are of a plastid/bacterial type, and distinct from those of the equivalent pathway in animals, fatty acid biosynthesis is potentially an excellent target for therapeutics directed against malaria, toxoplasmosis, and other apicomplexan-mediated diseases.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.95.21.12352
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1998
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  • 4
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    Online Resource
    Evolutionary cell biology: Two origins, one objective
    Proceedings of the National Academy of Sciences ; 2014
    In:  Proceedings of the National Academy of Sciences Vol. 111, No. 48 ( 2014-12-02), p. 16990-16994
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 111, No. 48 ( 2014-12-02), p. 16990-16994
    Abstract: All aspects of biological diversification ultimately trace to evolutionary modifications at the cellular level. This central role of cells frames the basic questions as to how cells work and how cells come to be the way they are. Although these two lines of inquiry lie respectively within the traditional provenance of cell biology and evolutionary biology, a comprehensive synthesis of evolutionary and cell-biological thinking is lacking. We define evolutionary cell biology as the fusion of these two eponymous fields with the theoretical and quantitative branches of biochemistry, biophysics, and population genetics. The key goals are to develop a mechanistic understanding of general evolutionary processes, while specifically infusing cell biology with an evolutionary perspective. The full development of this interdisciplinary field has the potential to solve numerous problems in diverse areas of biology, including the degree to which selection, effectively neutral processes, historical contingencies, and/or constraints at the chemical and biophysical levels dictate patterns of variation for intracellular features. These problems can now be examined at both the within- and among-species levels, with single-cell methodologies even allowing quantification of variation within genotypes. Some results from this emerging field have already had a substantial impact on cell biology, and future findings will significantly influence applications in agriculture, medicine, environmental science, and synthetic biology.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1415861111
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2014
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  • 5
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    Online Resource
    Apicomplexan Parasites Co-Opt Host Calpains to Facilitate Their Escape from Infected Cells
    American Association for the Advancement of Science (AAAS) ; 2009
    In:  Science Vol. 324, No. 5928 ( 2009-05-08), p. 794-797
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 324, No. 5928 ( 2009-05-08), p. 794-797
    Abstract: Apicomplexan parasites, including Plasmodium falciparum and Toxoplasma gondii (the causative agents of malaria and toxoplasmosis, respectively), are responsible for considerable morbidity and mortality worldwide. These pathogenic protozoa replicate within an intracellular vacuole inside of infected host cells, from which they must escape to initiate a new lytic cycle. By integrating cell biological, pharmacological, and genetic approaches, we provide evidence that both Plasmodium and Toxoplasma hijack host cell calpain proteases to facilitate parasite egress. Immunodepletion or inhibition of calpain-1 in hypotonically lysed and resealed erythrocytes prevented the escape of P. falciparum parasites, which was restored by adding purified calpain-1. Similarly, efficient egress of T. gondii from mammalian fibroblasts was blocked by either small interfering RNA–mediated suppression or genetic deletion of calpain activity and could be restored by genetic complementation.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1171085
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2009
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  • 6
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    Measuring tubulin content in Toxoplasma gondii : A comparison of laser-scanning confocal and wide-field fluorescence microscopy
    Proceedings of the National Academy of Sciences ; 2002
    In:  Proceedings of the National Academy of Sciences Vol. 99, No. 4 ( 2002-02-19), p. 2014-2019
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 99, No. 4 ( 2002-02-19), p. 2014-2019
    Abstract: Toxoplasma gondii is an intracellular parasite that proliferates within most nucleated cells, an important human pathogen, and a model for the study of human and veterinary parasitic infections. We used a stable yellow fluorescent protein-α-tubulin transgenic line to determine the structure of the microtubule cytoskeleton in T. gondii . Imaging of living yellow fluorescent protein-α-tubulin parasites by laser-scanning confocal microscopy (LSCM) failed to resolve the 22 subpellicular microtubules characteristic of the parasite cytoskeleton. To understand this result, we analyzed sources of noise in the LSCM and identified illumination fluctuations on time scales from microseconds to hours that introduce significant amounts of noise. We confirmed that weakly fluorescent structures could not be imaged in LSCM by using fluorescent bead standards. By contrast, wide-field microscopy (WFM) did visualize weak fluorescent standards and the individual microtubules of the parasite cytoskeleton. We therefore measured the fluorescence per unit length of microtubule by using WFM and used this information to estimate the tubulin content of the conoid (a structure important for T. gondii infection) and in the mitotic spindle pole. The conoid contains sufficient tubulin for ≈10 microtubule segments of 0.5-μm length, indicating that tubulin forms the structural core of the organelle. We also show that the T. gondii mitotic spindle contains ≈1 microtubule per chromosome. This analysis expands the understanding of structures used for invasion and intracellular proliferation by an important human pathogen and shows the advantage of WFM combined with image deconvolution over LSCM for quantitative studies of weakly fluorescent structures in moderately thin living cells.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.022554999
    RVK:
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2002
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  • 7
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    A Plastid of Probable Green Algal Origin in Apicomplexan Parasites
    American Association for the Advancement of Science (AAAS) ; 1997
    In:  Science Vol. 275, No. 5305 ( 1997-03-07), p. 1485-1489
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 275, No. 5305 ( 1997-03-07), p. 1485-1489
    Abstract: Protozoan parasites of the phylum Apicomplexa contain three genetic elements: the nuclear and mitochondrial genomes characteristic of virtually all eukaryotic cells and a 35-kilobase circular extrachromosomal DNA. In situ hybridization techniques were used to localize the 35-kilobase DNA of Toxoplasma gondii to a discrete organelle surrounded by four membranes. Phylogenetic analysis of the tufA gene encoded by the 35-kilobase genomes of coccidians T. gondii and Eimeria tenella and the malaria parasite Plasmodium falciparum grouped this organellar genome with cyanobacteria and plastids, showing consistent clustering with green algal plastids. Taken together, these observations indicate that the Apicomplexa acquired a plastid by secondary endosymbiosis, probably from a green alga.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.275.5305.1485
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 1997
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  • 8
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    Bioinformatics--Trying to Swim in a Sea of Data
    American Association for the Advancement of Science (AAAS) ; 2001
    In:  Science Vol. 291, No. 5507 ( 2001-02-16), p. 1260-1261
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 291, No. 5507 ( 2001-02-16), p. 1260-1261
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.291.5507.1260
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2001
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  • 9
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    O -fucosylated glycoproteins form assemblies in close proximity to the nuclear pore complexes of Toxoplasma gondii
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 41 ( 2016-10-11), p. 11567-11572
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 41 ( 2016-10-11), p. 11567-11572
    Abstract: Toxoplasma gondii is an intracellular parasite that causes disseminated infections in fetuses and immunocompromised individuals. Although gene regulation is important for parasite differentiation and pathogenesis, little is known about protein organization in the nucleus. Here we show that the fucose-binding Aleuria aurantia lectin (AAL) binds to numerous punctate structures in the nuclei of tachyzoites, bradyzoites, and sporozoites but not oocysts. AAL also binds to Hammondia and Neospora nuclei but not to more distantly related apicomplexans. Analyses of the AAL-enriched fraction indicate that AAL binds O -linked fucose added to Ser/Thr residues present in or adjacent to Ser-rich domains (SRDs). Sixty-nine Ser-rich proteins were reproducibly enriched with AAL, including nucleoporins, mRNA-processing enzymes, and cell-signaling proteins. Two endogenous SRDs-containing proteins and an SRD-YFP fusion localize with AAL to the nuclear membrane. Superresolution microscopy showed that the majority of the AAL signal localizes in proximity to nuclear pore complexes. Host cells modify secreted proteins with O -fucose; here we describe the O -fucosylation pathway in the nucleocytosol of a eukaryote. Furthermore, these results suggest O -fucosylation is a mechanism by which proteins involved in gene expression accumulate near the NPC.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1613653113
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
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  • 10
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    Themes and Variations in Apicomplexan Parasite Biology
    American Association for the Advancement of Science (AAAS) ; 2005
    In:  Science Vol. 309, No. 5731 ( 2005-07), p. 72-73
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 309, No. 5731 ( 2005-07), p. 72-73
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1115252
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2005
    detail.hit.zdb_id: 128410-1
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    detail.hit.zdb_id: 2060783-0
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