Fig. 1.

Three-dimensional organization of the apical complex in Toxoplasma tachyzoites reveals the subpellicular microtubule and conoid architecture. (A) Cartoon of the Toxoplasma tachyzoite, the life stage of which has been imaged by cryo-ET in B and annotated in E. (B) Tomographic slice of a representative apical complex of an intact tachyzoite recorded with VPP optics in a 200-kV electron microscope. The dotted and solid rectangles show the regions of the apical complex represented in greater detail in C and D using different z slices (scale bar, 100 nm). (C) A zoomed-in view of a tomographic slice in the dashed black rectangle of B, showing two CFs in the xy plane, their anterior ends extending toward a PCR (white bracket) with filamentous density (a white arrowhead) between them (scale bar, 25 nm). (D) Portion of a tomographic slice in the black rectangle of B, showing the SPMTs in the xy plane, and their association with the APR (white bracket). Note columnar densities (white arrows) emerging from the APR and positioned between the SPMTs (scale bar, 25 nm). (E) Three-dimensional segmentation of the tomogram shown in B including the PCR (red), CFs (cyan), APRs (golden), SPMTs (blue), intraconoidal microtubules (red), micronemes (pink), rhoptries (yellow), and plasma membrane (pale pink) (scale bar, 100 nm). A movie with the complete tomogram is available in SI Appendix, Movie S1.