Summary: During cytokinesis, a contractile ring consisting of unbranched filamentous actin (F-actin) and myosin II 70 qt storage bin constricts at the cell equator.Unbranched F-actin is generated by formin, and without formin no cleavage furrow forms.In Caenorhabditis elegans, depletion of septin restores furrow ingression in formin mutants.How the cleavage furrow ingresses without a detectable unbranched F-actin ring is unknown.
We report that, in this setting, anillin (ANI-1) forms a meshwork of circumferentially aligned linear structures decorated by non-muscle myosin II (NMY-2).Analysis of ANI-1 deletion mutants reveals that its disordered N-terminal half is required for linear structure formation and sufficient for furrow ingression.NMY-2 promotes the circumferential alignment 2.75x100 of the linear ANI-1 structures and interacts with various lipids, suggesting that NMY-2 links the ANI-1 network with the plasma membrane.Collectively, our data reveal a compensatory mechanism, mediated by ANI-1 linear structures and membrane-bound NMY-2, that promotes furrowing when unbranched F-actin polymerization is compromised.