Fig. 3. The increase in PtdIns(4,5)P₂ is polarized to the vegetal pole. (A) Changes in [Ca²⁺]_i and PH-GFP distribution at fertilization in an egg in which the confocal slice was taken through both the animal and vegetal poles. Drawing on right illustrates the regions selected for measurements of PM and C fluorescence in the animal (dark/light blue) and vegetal (dark/light green) poles. Changes in PM/C in the vegetal and animal poles are illustrated by a red or orange trace, respectively. For abbreviations, see Fig. 2 legend. (B) GFP images corresponding to selective time points (arrowheads numbered 1-3 in A) for the experiment described in A. The lower region of the egg (red box) was expanded and displayed in pseudocolor to show more clearly the changes in fluorescence intensity.