Abnormal morphology of MCs is observed in RBCs infected with mature-stage parasites. (A) Immunofluorescence analysis of 3D7 or 3D7ΔPf332 (11G7 or 13E2) schizont-infected RBCs containing 8 or more DAPI-stained nuclei. MCs were visualized with antibodies raised against SBP1. Greater than 60% of transgenic Pf332KO iRBCs showed fewer and abnormally large MCs compared with 3D7 iRBCs. A total of 2 typical iRBCs are shown for each parasite line. (B) Electron micrographs of thin sections through RBCs infected with late-stage parasites (P), either the parental line (3D7) or the Pf332 KO clone (11G7), showing the ultrastructure and arrangement of Maurer clefts (MC) underlying the RBC membrane (RBCM). Note that MCs are stacked and aggregated in the absence of Pf332.