Fig. 3. MORN1 is associated with the nucleus and undergoes cell cycle dependent changes. (A-C) Combined MORN1 antibody (green) and DNA staining using DAPI (blue) reveals a structure (arrowhead) associated with the nucleus that doubles (B, note higher DNA content) and associates with the daughters during division (C). (D) DNA content of nuclei was measured by image analysis of DAPI-stained preparations and plotted against the number of nuclear MORN1 dots (n=105, P<0.0001). (E-G) Co-staining of MORN1 with anti--tubulin antibody resulted in colocalization of nuclear MORN1 (arrowhead) and tubulin (F). (H-K) In vivo labeling using a MORN1-YFP transgene (see 3D projection of this dataset as Movies 1 and 2 in the supplementary material). These parasites were transfected with (I) GRASP55-RFP (Golgi), (J) FNR-RFP (apicoplast) and (K) centrin-RFP (centrosome). (L-Q) Immunoelectron microscope analysis of MORN1 structures. (L) Gold particles mark the posterior end of a tachyzoite (arrowheads), higher magnification of the same area (M) shows the labeling at the inside of the IMC. In parasite cross sections the MORN1 antibody labels a ring structure (N). O shows a tachyzoite early in division. White arrowheads highlight the newly forming daughter IMC apical of the nucleus (N). The centrocone (black arrow) appears electron dense in the lumen and below the membrane that separates it from the nucleoplasm (see Fig. 7E for a schematic view of this structure). (P,Q) Higher magnifications show gold particles located with this dense material. The edge of the daughter IMC (white arrowheads) is equally labeled.