Comparative biology of cell division in the fission yeast clade

Abstract

Cytokinesis must be regulated in time and space in order to preserve genome integrity during cell proliferation and to allow daughter cells to adopt distinct fates and geometries during differentiation. The fission yeast Schizosaccharomyces pombe has been a popular model organism for understanding spatiotemporal regulation of cytokinesis in a symmetrically dividing cell. Recent work on another member of the same genus, Schisozaccharomyces japonicus, suggests that S. pombe may have evolved an unusual division site placement mechanism based on a recently duplicated anillin paralog. Here we discuss an extraordinary evolutionary plasticity of cytokinesis within the fission yeast clade and argue that the comparative cell biology approach may provide functional insights beyond those afforded by scrutinizing individual model species.

Figure 1. Diagrams summarizing the modes of mitosis and cytokinesis in S. pombe (left) and S. japonicus (right).

Pictorial legend is included.

Figure 2. A diagram describing two modes of myosin II recruitment (Mid1- and Cdc15-dependent) to the equatorial cortex and ring assembly in fission yeasts.

Core cytokinetic ring components (in black) include the anillin-like protein Mid1, F-BAR domain protein Cdc15, IQGAP protein Rng2, myosin II heavy chain Myo2, myosin essential light chain Cdc4 and the cytokinetic formin Cdc12. Direction of black arrows indicates hierarchical organization of ring components according to protein localization dependency in cortical recruitment. Regulatory cascades controlling ring assembly and function are shown in grey outer area. The Polo kinase Plo1 and Septation Initiation Network coordinate actomyosin ring assembly and constriction through controlling phosphorylation status of core ring components. The tip-localized DYRK family protein kinase Pom1 prevents ring assembly at cell ends by inhibiting clustering of Mid1/Cdr2 nodes and likely keeping the mitotic myosin anchor Cdc15 in its inactive, “closed” conformation. Direct (solid lines) and genetic (dotted lines) interactions are mostly based on S. pombe data.