Post‐mitotic cellular reorganisation in the diatom Cymatopleura solea: The role of microtubules and the microtubule centre

This is the authors' abstract. We don't add key points for this paper.

Cell division in Cymatopleura requires precise and major relocations of the nucleus and chioroplast which have been followed by time‐lapse cinematography and with the electron microscope. These movements are (1) the premitotic nucleus migrating to one end of the cell; (2) after cytokinesis, the daughter nuclei moving back to the cell centre, often oscillating several times while establishing their final location; (3) the single chloroplast folding over and sandwiching the central nucleus; and (4) the folded end of the chloroplast stretching back to fill the empty half of the cell. In all cases, straight, actively moving, transient strands of cytoplasm are associated with the movement of the nucleus and chloroplast, and these often appear to be pulling on the surface or the fold of the chloroplast which undergoes transient distortion. These movements are rapid and colchicine‐sensitive. Ultrastructurally, they appear to be mediated by the prominent microtubule centre (MC) and its associated cytoskeleton of microtubules (MTs) although MTs do not attach directly to either nucleus or chloroplast. The MC is located close to the moving nucleus. Later, it moves ahead of the moving chloroplast and its MTs ensheath the tip. Later still, it is seen embedded in the fold of the chloroplast. In all three situations, MTs from it are seen in the strands of cytoplasm radiating from this area across the vacuole. After these events, the MC resumes its usual interphase situation on the nuclear surface.