Rewiring of cellular division site selection in evolution of fission yeasts

Ying Gu,Candice Yam,Snezhana Oliferenko

doi:10.1016/j.cub.2015.02.056

Abstract

SummaryStrategies to position the division apparatus exhibit a bewildering diversity [1], but how these mechanisms evolve remains virtually unknown. Here, we explore the plasticity of division site positioning in fission yeasts Schizosaccharomyces pombe and Schizosaccharomyces japonicus. We demonstrate that, whereas both species divide in the middle, only S. pombe uses the anillin Mid1 as a primary nucleus-derived cue to assemble the actomyosin ring at the equatorial cortex. We trace this variance to the divergence in subcellular targeting of Mid1 and show that duplication of an ancestral anillin early in the Schizosaccharomyces lineage may have led to subfunctionalization of the Mid1 orthologs. In contrast to S. pombe, medial assembly of the actomyosin ring in mitotic S. japonicus relies on the cortical anchor protein Cdc15 regulated by the tip-localized kinase Pom1. Our data suggest that division site placement is determined by cortical positioning of the actomyosin-plasma membrane linkers and that both identity of the linker and control of its subcellular targeting are highly modular.

Highlights

S. japonicus did not initiate equatorial actin assembly until late anaphase, consistent with early observations of fixed cells [3]
In the related species S. japonicus, the myosin II marked by the regulatory light chain Rlc1-GFP formed an equatorial band of cortical nodes already in interphase
In line with bipolar F-actin distribution, mitotic S. japonicus cells elongated until the actomyosin ring assembly (Figure S1C; 2 ± 1.1 mm/hr; n = 8 cells)

Summary

Introduction

S. japonicus did not initiate equatorial actin assembly until late anaphase, consistent with early observations of fixed cells [3]. Whereas S. japonicus Mid1 serves as an interphase cortical anchor for myosin, it is dispensable for ring assembly at the cellular equator. The fact that myosin is recruited to the equatorial cortex during cytokinesis in S. japonicus cells lacking the interphase scaffold Mid1 suggested the existence of other cortical actomyosin anchor(s).

Results

Conclusion