Fig. 1. Translocation of dorsal determinants and GBP-GFP during cortical rotation. (A) Diagram of translocation events during cortical rotation. Before cortical rotation (left), dorsal determinants are present in the vegetal shear zone. After cortical rotation (top right), the cortex has rotated 30° relative to the core cytoplasm toward the prospective dorsal side, and dorsal determinants have translocated in the same direction beyond the extent of cortical displacement. In an experimental situation (bottom right), the cortex is immobilized, and eggs are imaged from the vegetal pole with an inverted scanning laser confocal microscope. From the perspective of the viewer, the core cytoplasm appears to undergo a reverse rotation following activation, and the dorsal determinants translocate in the opposite direction. Note that the relative displacement of the core cytoplasm, cortex and determinants after rotation is the same in the normal and experimental situations. (B) GBP-GFP particles exhibit fast transport opposite the direction of the yolk during cortical rotation. Time-lapse images of the vegetal shear zone of an activated egg showing movements of GBP-GFP (green) during cortical rotation. Position of yolk platelets was inferred from dark areas in the GFP channel. First frame of sequence shows starting position of three GBP-GFP particles (yellow circles) and three yolk platelets (asterisks). (B') Same field of view 90 seconds later showing paths (yellow arrows) taken by the GBP-GFP particles moving from left to right and yolk platelets (Y) moving from right to left. See Movie 1 (http://dev.biologists.org/supplemental/) to view time-lapse movie of GBP-GFP particle translocation during cortical rotation.