Fig. 1. Immunolocalisation of tubulin. (A) tubulin localisation and cell cycle progression. Cells are arranged in order of mitotic progression from G₂ (1) through mitosis (2,3) to septation (4-7), and back into G₂ once more (8). tubulin was found on the SPB throughout the cell cycle, appeared at the cell equator during anaphase B (3) and persisted (cells 4-7) until septation was complete (compare 7 and 8). Note that fission yeast do not extrude a structure containing tubulin as mammalian cells do with a mid-body, instead they retain medial tubulin and divide it between the two new daughter cells (7). (B,C) Wild-type cells were stained with a mixture of rabbit anti--tubulin (red) and mouse anti--tubulin (green) antibodies and then processed to stain with DAPI (blue) before imaging. Optical sections were processed by the application of deconvolution algorithms. In each panel, the left hand figure shows a projection of all of the images into a single plane of view, whereas the smaller numbered panels show sections through the series that produced this image from top (1) to bottom (2). (B) Not all regions of the EMTOC that contain tubulin staining are associated with the ends of microtubules (arrow). (C) The upper large arrowhead shows the EMTOC. The two small arrowheads highlight cortical spots of tubulin staining that are associated with microtubule ends. (D) 3D deconvolution of tubulin staining shows that the EMTOC is not a continuous ring. The left hand panel shows a projection of a cell that contains an EMTOC, whereas the right hand, numbered, panels show four snap shots, as a 3D reconstruction of this structure was rotated through 360° in the direction indicated by the red arrow. The EMTOC in this cell is composed of two crescents of tubulin staining that face each other from opposite sides of the cell equator.

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