RGA-3/4 localizes to the equatorial cortex and contractile ring in Xenopus embryos. (A) Time course of F-actin and RGA-3/4^WT-3xGFP in Xenopus embryo epithelial cell undergoing cytokinesis. Time in min:s, F-actin (mCherry-UtrCH, top) and RGA-3/4^WT-3xGFP (bottom). RGA-3/4 signal accumulates at equatorial cortex coincident with F-actin localization and persists throughout cytokinesis (see also Video 6). Scale bar = 25 µm. (B) GAP-dead RGA-3/4 localizes to cortical waves, the equatorial cortex and contractile ring in Xenopus embryos. Time course of single cell in early frog embryo undergoing cytokinesis. Tagged, GAP-dead RGA-3/4 (RGA-3/4^R80E-3xGFP) localizes to cortical waves (29:44, 33:36), equatorial cortex (36:52), and contractile ring (37:48 and 42:56); see also Video 7. Scale bar = 25 µm. (B′) Kymograph generated from region indicated by dotted line in B. Positions of still frames in B indicated on kymograph with white dashes. Waves in furrow region are labeled with white arrowheads. x scale bar = 25 µm, y scale bar = 2 min. (C) RGA-3/4 and actin colocalize in furrow waves. Time course of cell in dividing frog embryo expressing mCherry-UtrCH (actin; top) and RGA-3/4^R80E-3XGFP (bottom). Scale bar = 25 µm. (C′) Kymographs correspond to dotted yellow line (panel 1). Kymographs generated from raw data (left) and difference subtraction data (right); x scale bar = 5 µm, y scale bar = 2 min. Inset from box 1 is magnified 1.4×; x scale bar = 5 µm, y scale bar = 2 min.