Fig 4. Knockdown of PfVP1 alters the cytosolic pH and PPi levels.

A, In the 3D7-PfVP2KO-PfVP1-3HA^apt line, pH was measured in the control culture (aTc, +), the knockdown culture after aTc removal for 48 h from the schizont stage (aTc, -), and the addback culture after aTc re-administration for 48 h from day 2 to day 4 (aTc, -/+). pH was measured using BCECF in a spectrofluorometer (Hitachi F-7000). Mean±s.d. of 6 measurements are shown. B, pH measurement of aTc plus and minus cultures challenged with IDP (imidodiphosphate). At 48 h post knockdown, IDP (0.2 mM) was added to the saponin treated parasites before pH measurement. Mean±s.d. of 3 measurements are shown. C, PPi measurement in the knockdown parasites after aTc removal for 72, 84, and 96 h from the schizont stage. Mean±s.d. of 3–4 measurements are shown. In A-C, statistical analysis was done by Student t-test. P values are shown in each panel. Experiments of A and B were repeated twice. Experiments of C were repeated three times.