Abstract

The coccidian subgroup of Apicomplexa possesses an apical complex harboring a conoid, made of unique tubulin polymer fibers. This enigmatic organelle extrudes in extracellular invasive parasites and is associated to the apical polar ring (APR). The APR serves as microtubule-organizing center for the 22 subpellicular microtubules (SPMTs) that are linked to a patchwork of flattened vesicles, via an intricate network composed of alveolins. Here, we capitalize on ultrastructure expansion microscopy (U-ExM) to localize the Toxoplasma gondii Apical Cap protein 9 (AC9) and its partner AC10, identified by BioID, to the alveolin network and intercalated between the SPMTs. Parasites conditionally depleted in AC9 or AC10 replicate normally but are defective in microneme secretion and fail to invade and egress from infected cells. Electron microscopy revealed that the mature parasite mutants are conoidless, while U-ExM highlighted the disorganization of the SPMTs which likely results in the catastrophic loss of APR and conoid.

Data availability

All data generated or analysed during this study are included in the manuscript and supplementary file 1

Article and author information

Author details

  1. Nicolò Tosetti

    Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
    Competing interests
    No competing interests declared.
  2. Nicolas Dos Santos Pacheco

    Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-1959-194X
  3. Eloïse Bertiaux

    Department of Cell Biology, University of Geneva, Geneva, Switzerland
    Competing interests
    No competing interests declared.
  4. Bohumil Maco

    Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
    Competing interests
    No competing interests declared.
  5. Lorène Bournonville

    Department of Cell Biology, University of Geneva, Geneva, Switzerland
    Competing interests
    No competing interests declared.
  6. Virginie Hamel

    Department of Cell Biology, University of Geneva, Geneva, Switzerland
    Competing interests
    No competing interests declared.
  7. Paul Guichard

    Department of Cell Biology, University of Geneva, Geneva, Switzerland
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-0363-1049
  8. Dominique Soldati-Favre

    Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
    For correspondence
    Dominique.Soldati-Favre@unige.ch
    Competing interests
    Dominique Soldati-Favre, Senior editor, eLife.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-4156-2109

Funding

Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (310030_185325 and PP00P3_187198)

  • Dominique Soldati-Favre

H2020 European Research Council (695596 and 695596)

  • Dominique Soldati-Favre

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Copyright

© 2020, Tosetti et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

Metrics

  • 3,587
    views
  • 473
    downloads
  • 94
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Nicolò Tosetti
  2. Nicolas Dos Santos Pacheco
  3. Eloïse Bertiaux
  4. Bohumil Maco
  5. Lorène Bournonville
  6. Virginie Hamel
  7. Paul Guichard
  8. Dominique Soldati-Favre
(2020)
Essential function of the alveolin network in the subpellicular microtubules and conoid assembly in Toxoplasma gondii
eLife 9:e56635.
https://doi.org/10.7554/eLife.56635

Share this article

https://doi.org/10.7554/eLife.56635

Further reading

    1. Ecology
    2. Microbiology and Infectious Disease
    Benedikt M Mortzfeld, Shakti K Bhattarai, Vanni Bucci
    Short Report

    Interspecies interactions involving direct competition via bacteriocin production play a vital role in shaping ecological dynamics within microbial ecosystems. For instance, the ribosomally produced siderophore bacteriocins, known as class IIb microcins, affect the colonization of host-associated pathogenic Enterobacteriaceae species. Notably, to date, only five of these antimicrobials have been identified, all derived from specific Escherichia coli and Klebsiella pneumoniae strains. We hypothesized that class IIb microcin production extends beyond these specific compounds and organisms. With a customized informatics-driven approach, screening bacterial genomes in public databases with BLAST and manual curation, we have discovered 12 previously unknown class IIb microcins in seven additional Enterobacteriaceae species, encompassing phytopathogens and environmental isolates. We introduce three novel clades of microcins (MccW, MccX, and MccZ), while also identifying eight new variants of the five known class IIb microcins. To validate their antimicrobial potential, we heterologously expressed these microcins in E. coli and demonstrated efficacy against a variety of bacterial isolates, including plant pathogens from the genera Brenneria, Gibbsiella, and Rahnella. Two newly discovered microcins exhibit activity against Gram-negative ESKAPE pathogens, i.e., Acinetobacter baumannii or Pseudomonas aeruginosa, providing the first evidence that class IIb microcins can target bacteria outside of the Enterobacteriaceae family. This study underscores that class IIb microcin genes are more prevalent in the microbial world than previously recognized and that synthetic hybrid microcins can be a viable tool to target clinically relevant drug-resistant pathogens. Our findings hold significant promise for the development of innovative engineered live biotherapeutic products tailored to combat these resilient bacteria.

    1. Microbiology and Infectious Disease
    Francesca Torelli, Diogo M da Fonseca ... Moritz Treeck
    Research Article

    Toxoplasma gondii is an intracellular parasite that subverts host cell functions via secreted virulence factors. Up to 70% of parasite-controlled changes in the host transcriptome rely on the MYR1 protein, which is required for the translocation of secreted proteins into the host cell. Mice infected with MYR1 knock-out (KO) strains survive infection, supporting a paramount function of MYR1-dependent secreted proteins in Toxoplasma virulence and proliferation. However, we have previously shown that MYR1 mutants have no growth defect in pooled in vivo CRISPR-Cas9 screens in mice, suggesting that the presence of parasites that are wild-type at the myr1 locus in pooled screens can rescue the phenotype. Here, we demonstrate that MYR1 is not required for the survival in IFN-γ-activated murine macrophages, and that parasites lacking MYR1 are able to expand during the onset of infection. While ΔMYR1 parasites have restricted growth in single-strain murine infections, we show that the phenotype is rescued by co-infection with wild-type (WT) parasites in vivo, independent of host functional adaptive immunity or key pro-inflammatory cytokines. These data show that the major function of MYR1-dependent secreted proteins is not to protect the parasite from clearance within infected cells. Instead, MYR-dependent proteins generate a permissive niche in a paracrine manner, which rescues ΔMYR1 parasites within a pool of CRISPR mutants in mice. Our results highlight an important limitation of otherwise powerful in vivo CRISPR screens and point towards key functions for MYR1-dependent Toxoplasma-host interactions beyond the infected cell.