Fig. 7. Distribution of mitochondria, microfilaments, microtubules and aPKC protein in CAB-containing blastomeres. (A) B5.2 cells labelled for mitochondria (posterior view). Dotted white line indicates plasma membranes between blastomeres. The dome-shaped CAB is apparent as a mitochondria-free domain (arrow). (B,C) B5.2 cells double labelled for aPKC (green) and mitochondria (red); vegetal views. Arrowhead indicates the cortical face of the CAB; arrow indicates the mitochondria-free space occupied by the cER-mRNA domain and dense granules as in A. Movie 3 in supplementary material displays a series of confocal z sections through a similarly labelled embryo. (D) 8-cell stage embryo double labelled for aPKC (green) and actin microfilaments (red). Posterior vegetal portion of B4.1 cell is shown. (E-G) Isolated cortical fragments from posterior face of 8-cell stage embryo, double-labelled for aPKC (green) and ER (red). (E) One CAB; the aPKC protein (green) is concentrated in particles filling part of the space between ER sheets and tubes (red) which are densely packed in the CAB. (F) Thin confocal sections taken of a pair of CABs, proceeding from the plasma membrane (z1) into the cell (z3, z5), in increments of 0.16 µm, showing that the aPKC-rich layer is closer to the plasma membrane than the ER. (G) Intensity profile of the two signals along the x-z axis; plasma membrane is on the bottom; cytoplasm on top. (H-M) Posterior vegetal blastomeres double-labelled for aPKC (green) and tubulin (red); c, centrosome. (H-J) B5.2 cells in interphase; dotted white lines indicate the position and shape of the nuclei (n) as projected from other focal planes. (K) B4.1 cell in prophase; n, nucleus. Movie 4 in supplementary material shows the complete series of confocal z sections through this cell. (L) B5.2 cells in prometaphase. (M) B5.2 cells in metaphase (above) and anaphase (below). DNA is labelled in blue. Bars, 10 µm.