Dynamics of separase and securin during meiosis I. (A) Endogenously tagged SEP-1::mScarlet (green) and IFY-1::GFP (magenta) colocalize on the spindle at the metaphase to anaphase transition. Securin is rapidly degraded while separase relocalizes to the midbivalent (yellow caret) at anaphase onset (time shown in seconds, t = 0 is anaphase onset). (B) Cortical images of SEP-1::mScarlet (magenta) and IFY-1::GFP (green). IFY-1::GFP colocalizes with SEP-1::mScarlet on linear elements (yellow arrow) until it is degraded before separase relocalizes to vesicles (time shown in seconds, t = 0 marks vesicle localization). (C) Quantification of cytoplasmic securin levels in different WT or mutant securin GFP lines (t = 0 denotes anaphase onset). (C′) Cytoplasmic GFP levels measured in embryos 300 s before anaphase showing similar expression in WT1 and DM1 lines used throughout the manuscript. (D) Images of endogenously tagged SEP-1::mScarlet (green) and Tubulin::mCherry (magenta) show polar enriched separase within the tubulin cage and midbivalent separase (yellow caret) between microtubule bundles. (E–H) Endogenously tagged SEP-1::mScarlet (green) colocalizes with CZW-1::GFP (magenta, Yamamoto et al., 2008) at kinetochores during prometaphase I, partially colocalizes with CZW-1::GFP at the spindle pole (yellow caret) before midbivalent localization in anaphase. Scale bars: 5 µm.