FIGURE 5: The Δtgpts strain is deficient in the storage of subcellular calcium. Calcium-induced fluorescence in the two GECI-strains following exposure to 8 % ethanol (A) or to 5 µM A23187 (B) (42 hrs post-infection). Human fibroblasts were infected with transgenic parental or Δtgpts strains. As shown in Fig. 4B, the number of intracellular tachyzoites was equivalent in the two strains. Note that EGFP fluorescence signals just prior to drug exposure (0 min) are nearly equal, indicating a comparable number of vacuoles (and thus GECI activity) in both strains. Graphs show the mean ± SEM from 6 assays (student’s t-test, ***p<0.001).