Fig. 7. Plastid fission concurs with the last mitosis and cytokinesis. (A-D) In order to precisely time plastid fission the micronemal protein SnMic10 was used as molecular marker. Infected cultures were fixed 72 hours post-infection and labeled with antibodies to SnMIC10 (red), ACP (green) and DAPI (blue). (A) Three S. neurona stages: (1) developing schizont, (2) late schizont initiating budding and (3) final stage schizont with emerging daughter cells. (B) Expression of SnMIC10 coincides with budding and daughter cell formation and is undetectable in developing schizont (see also Hoane et al., 2003). (C,D) In the absence of SnMIC10 expression, plastids are always tubular (D, 1) and plastid fission concurs with the onset of SnMIC10 expression (C). (E-H) Cultures were also triple labeled for plastid, microtubules and DNA. Concurrent with the formation of daughter cell buds (red halos in inset in F), the plastid labeled with anti-ACP antibody starts to fragment (E). Merged images of anti--tubulin and anti-ACP staining (G) revealed that plastid spindle pole association is maintained through this last division similar to plastid segregation in T. gondii (Striepen et al., 2000). Note that the nuclear DNA is still unsegregated. The emerging fully separated merozoites each contain a nucleus and a plastid (D 3).