Fig. 6. Overexpression of MORN1-RFP abolishes parasite cell division. (A-D) Expression of MORN1-RFP driven by the strong -tubulin promoter results in ring-shaped accumulations of RFP signal (24 hours after transfection) and morphological defects of the parasite. Note large size of cell (B) and nucleus (C) along with changes in shape when compared to untransfected controls (D). (E) Nuclear DNA content in transfected (+) and untransfected (-) parasites was quantified using image analysis 48 hours after transfection (arbitrary units of DAPI fluorescence; n=120, P<0.0001, error bar show standard deviation). (F-M) Parasites expressing IMC3-YFP (F-I, green) or YFP-tubulin (J-M, green) were transiently transfected with tubMORN1-RFP (red). Untransfected controls are shown in I and M. Some IMC3-YFP colocalized with MORN1 (arrows) but no discernable buds were formed. Multiple daughter tubulin baskets have been initiated and extended in the mutant, however, microtubules are not constricted at the posterior end as observed in the wild type (dotted lines in L and M). (N-P) RH-infected cultures were treated with 0.05 µM oryzalin and stained with anti-MORN1 (N) and anti-IMC1 (O) antibody. Note multiple overlapping MORN1 and IMC1 structures (arrowheads) and a single centrocone in the nucleus (arrow, P).