Figure 2.

Confocal sections through living embryos after injection with WGA–Alexa488. All pictures show the embryo from the side. N, nuclei. The embryos were grown at 25°C, a temperature that increases the rate of invagination compared with 20°C as shown in Fig. 1. (A and B) WGA label of the same embryo at different time points shown in different colors. At time 0 (A), WGA is broadly distributed at the plasma membrane surface. 14 min later, WGA is only detected between nuclei, and the apical membrane (dashed line) is unlabeled. This staining persists throughout invagination (B) and is shown 2 min apart in phase 2 (+12′ and +14′), phase 3 (+33′ and +35′) and phase 4 (+56′ and +58′). (C) Another embryo where WGA (arrowhead, top) colocalizes with the FC (bottom, arrowhead). (D) Scheme illustrating the changing distribution of the initial label (red) from its apical distribution to the FC. The green membrane represents the newly inserted unlabeled membrane. Bar, 5 μm.