Cell separation and the maintenance of cell integrity during cytokinesis in yeast: the assembly of a septum.

The cell division programme included in each cell specifies that, after anaphase, cytokinesis completes the process of producing two cells. With the exception of plant cells, whose peculiarities are out of the scope of this review, in all eukaryotic cells the cleavage furrow that forms late in anaphase bisects the mitotic spindle. Ingression of the furrow and the consequent synthesis of the new membrane are driven by a cortical actomyosin contractile ring (AMR or CAR). The complete contraction of this ring leads to cell separation. While this process is sufficient for cell separation in animal cells, fungal cells are surrounded by a cell wall structure, whose continuity must be maintained to preserve cell integrity during cytokinesis. This maintenance requires the production of a specialized region of the fungal cell wall called the septum, which physically separates mother and daughter cells. Throughout this review, we shall try to highlight the different molecular cues involved in septum formation in yeast, from the initial site selection to the final action of hydrolytic enzymes that produce cell separation.