Loss of CSAR1 protects the conoid upon ERK7 degradation. (A–D) Maximum intensity Z-projections of confocal stacks of the indicated parasite strains grown in ±IAA and visualized with GFP-tubulin (green) and an antibody against the apical cap marker ISP1 (magenta). Apical ends of parasites are indicated with orange arrows. Retained cytoskeleton in the Δcsar1 residual body is indicated with gray arrows. Scale bars are 5 μm. (E) Stills from live cell imaging of GFP-tubulin in dividing ERK7^AID parasites grown in ±IAA. The time before (−) and after (+) cytokinesis is indicated. Maternal conoid is indicated with an orange arrow (or orange star when degraded). Daughter conoids are indicated with gold stars at point of degradation. (F) Stills from Δcsar1 parasites imaged as in E. Scale bars in E and F are 2 μm. Annotations as above; yellow arrows indicate viable daughter conoids at end of division in +IAA media. (G–I) Negative-stained TEM of detergent-extracted cytoskeleton “ghosts” from the indicated strains and grown in ±IAA. (Representative of n ≥ 30 TEM images.)