The Ndc80-Ska module is essential for recovery from mono-orientation induced by kinetochore dynein following PP4 inhibition. (A and E) Selected images from time-lapse movies of one-cell embryos co-expressing GFP::histone H2B (HIS-11) and γ-tubulin::GFP (TBG-1). Time is relative to NEBD. A kymograph for ∆ska-1 + smk-1(RNAi) is also shown in A. Cartoon in E shows recruitment hierarchy at the outer kinetochore relevant for this figure. Arrows in E point to separating sister chromatids. Scale bars, 5 µm. (B) Chromosome span (mean of n embryos ± SEM) versus time relative to NEBD. Measurements were performed in embryos such as those shown in A. Conditions are color-coded as in A and E. (C) Successive frames from a time-lapse movie of a one-cell embryo expressing endogenous GFP::CENP-A (HCP-3) to mark centromeres. Top frame corresponds to late prometaphase. Arrows point to a pair of co-segregated sister chromatids which later separate. Scale bar, 2 µm. (D) Top left: Cartoon illustrating that phosphorylation site mutations in NDC-80's N-terminal tail promote Ska recruitment to kinetochores. Top right: Selected images from time-lapse movies of one-cell embryos expressing transgene-encoded WT or mutant (4A) NDC-80 in the background of GFP::histone H2B (HIS-58) and GFP::γ-tubulin (TBG-1). Time is relative to NEBD. Scale bar, 5 µm. Bottom: Chromosome span (mean of n embryos ± SEM) versus time relative to NEBD, measured in embryos such as those shown above the graph.