iGAMA knockdown parasites are defective in host cell attachment. (A) Red-green invasion assay of tachyzoites after 20 min of incubation with HFF cells. (B) Attachment of cytochalasin D-treated tachyzoites to HFF cells. Parasites were preloaded with calcein green AM and then incubated with cytochalasin D and allowed to attach to host cells for 15 min with cytochalasin D. BAPTA-AM-treated Δku80:Tati parasites are a negative control for attachment. (C) Timed invasion assay. Shown are the results of a red-green invasion assay of tachyzoites after 0.5, 1, 2, 4, or 8 h of incubation with HFF cells. (D) Induced-egress assay. Egress from vacuoles grown for 28 h in chamber slides was induced with the calcium ionophore A23187, and occupied versus unoccupied vacuoles were enumerated. (E) Modes of gliding motility. Parental and iGAMA+ATc tachyzoites with different types of gliding motility were enumerated by video microscopy. Data are the average ± the standard error of the mean of at least three independent experiments for all graphs. *, P < 0.05; ns, not significant.