TY - JOUR T1 - Flow-independent accumulation of motor-competent non-muscle myosin II in the contractile ring is essential for cytokinesis JF - bioRxiv DO - 10.1101/333286 SP - 333286 AU - DS Osorio AU - FY Chan AU - J Saramago AU - J Leite AU - AM Silva AU - AF Sobral AU - R Gassmann AU - AX Carvalho Y1 - 2018/01/01 UR - http://biorxiv.org/content/early/2018/05/31/333286.abstract N2 - Cytokinesis in animal cells requires the assembly of a contractile actomyosin ring, whose subsequent constriction physically separates the two daughter cells. Non-muscle myosin II (myosin) is essential for cytokinesis, but the role of its motor activity remains poorly defined. Here, we examine cytokinesis in C. elegans one-cell embryos expressing myosin motor mutants generated by genome editing. Motor-dead myosin, which is capable of binding F-actin, does not support cytokinesis, and embryos co-expressing motor-dead and wild-type myosin are delayed in cytokinesis. Partially motor-impaired myosin also delays cytokinesis and renders contractile rings more sensitive to reduced myosin levels. Thus, myosin motor activity, rather than its ability to cross-link actin filaments, drives contractile ring assembly and constriction. We further demonstrate that myosin motor activity is required for long-range cortical actin flows, but that flows per se play a minor role in contractile ring assembly. Our results suggest that flow-independent recruitment of motor-competent myosin to the cell equator is both essential and rate-limiting for cytokinesis. ER -