title: The fission yeast cytokinetic contractile ring regulates septum shape and closure.
abstract: During cytokinesis, fission yeast and other fungi and bacteria grow a septum that divides the cell in two. In fission yeast closure of the circular septum hole by the β-glucan synthases (Bgs) and other glucan synthases in the plasma membrane is tightly coupled to constriction of an actomyosin contractile ring attached to the membrane. It is unknown how septum growth is coordinated over scales of several microns to maintain septum circularity. Here, we documented the shapes of ingrowing septum edges by measuring the roughness of the edges, a measure of the deviation from circularity. The roughness was small, with spatial correlations indicative of spatially coordinated growth. We hypothesized that Bgs-mediated septum growth is mechanosensitive and coupled to contractile ring tension. A mathematical model showed that ring tension then generates almost circular septum edges by adjusting growth rates in a curvature-dependent fashion. The model reproduced experimental roughness statistics and showed that septum synthesis sets the mean closure rate. Our results suggest that the fission yeast cytokinetic ring tension does not set the constriction rate but regulates septum closure by suppressing roughness produced by inherently stochastic molecular growth processes.
authors.affiliation: Department of Physics, Columbia University, New York, NY 10027, USA.
authors.forename: Sathish
authors.initials: S
authors.lastname: Thiyagarajan
authors.affiliation: Department of Microbiology & Immunology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
authors.forename: Emilia Laura
authors.initials: EL
authors.lastname: Munteanu
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Arasada
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA Department of Cell Biology, Yale University, New Haven, CT 06520, USA.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Pollard
authors.affiliation: Department of Chemical Engineering, Columbia University, New York, NY 10027, USA bo8@columbia.edu.
authors.forename: Ben
authors.initials: B
authors.lastname: O'Shaughnessy
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D048749:Cytokinesis / Q000235:genetics / Q000502:physiology; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029702:Schizosaccharomyces pombe Proteins
keywords: Cell wall growth; Cytokinesis; Mechanosensitivity; Schizosaccharomyces pombe; Septation