Abstract
The conserved small Rho GTPase Cdc42 has recently reported to play a role in cytokinesis in fission yeast, Schizosaccharomyces pombe. While the role of Cdc42 in cell polarity has been widely studied, little is known about its role in the regulation of cytokinesis. Here we investigate specific roles of Cdc42 during cytokinesis in fission yeast. Cytokinesis in fission yeast involves the coupling of actomyosin ring constriction to division cell wall (septum) synthesis. Cdc42 activators have been shown to promote timely initiation of septum synthesis and proper septum morphology. However, direct evidence supporting a role for Cdc42 in these events are lacking. Using a thermosensitive cdc42 allele (cdc42-1625), we investigated the direct role of Cdc42 in cytokinesis. We show that Cdc42 is essential for recruitment of the major primary septum synthesizing enzyme Bgs1 during cytokinesis; and that disruption of Cdc42 activity, prevented the initiation of ring constriction. Further, we find that Cdc42 is required for proper localization of the septum digesting enzymes Eng1 and Agn1 at the division site. Thus, we demonstrate that Cdc42 is required during cytokinesis to enable primary septum synthesis, and proper cell separation.