Fig. 5. PtdIns(4,5)P₂ synthesis is a consequence of exocytosis. (A) Changes in [Ca²⁺]_i and PH-GFP distribution at fertilization in an egg treated with 100 nM jasplakinolide. Similar results were obtained in six eggs. (B) Changes in [Ca²⁺]_i and PH-GFP distribution at fertilization in an egg injected with 5 µM BoNT/A-LC. Similar results were obtained in nine eggs. (C) To illustrate the effect of jasplakinolide and BoNT/A on the kinetics of the rise in PtdIns(4,5)P₂, the traces obtained in the control experiment shown in Fig. 1C (red trace), and in the two experiments described above (green, jasplakinolide; blue, BoNT/A-LC) were aligned according to the first peak in [Ca²⁺]_i and superimposed. For abbreviations, see Fig. 2 legend. (D) FITC-LCA labelling on (i) unfertilized MII oocyte; (ii) control fertilized egg; and (iii) jasplakinolide (100 nM)-treated fertilized egg. For each condition, the equatorial plane (left) and another focal plane close to the surface (right) of the same cell are displayed. Note the incomplete ring of fluorescence in the equatorial planes, illustrating the cortical granule-free domain in the animal pole. Exocytosis is indicated by an increased fluorescence in the equatorial plane and by a punctate fluorescence in the section close to the surface. Similar patterns of staining were observed in at least 20 cells, for each condition.