Figure 2.
Reduced levels of CYK-1 lead to ruptures, small discontinuities, and detached fibers in the contractile ring. (A) Instantaneous ring perimeter change versus ring perimeter in ABa/p cells. Each circle represents the ring perimeter change between two time points that are 10 s apart. 11 contractile rings were analyzed per condition. (B) Images of NMY-2::GFP in cyk-1(RNAi) rings showing a large rupture that leads to a transient regression (top row, blue arrow), small discontinuities that lead to a transient regression (second row, orange arrows), and small discontinuities that result in no or minimal ring ingression (third and fourth rows, orange arrows). Overlaid images are shown on the right (first time point in red, second in green, and third in blue). (C) Stills of cyk-1(RNAi) rings showing a small discontinuity. (D) Plot of myosin intensity profile along the ring peripheral arc before, during, and 40 s after rupture. Overlaid images are shown on top (before rupture in red, rupture in green, and 40 s after rupture in magenta). (E) Individual curves of mean NMY-2::GFP signal intensity over time, before and after ruptures, in five contractile rings. Intensity signal was measured as indicated on the schematic. (F) Images of cyk-1(RNAi) rings showing fibers detaching from the contractile ring (green arrows) at different time points during constriction. (G) Images of a contractile ring expressing LifeAct::GFP after treatment with 2.5 µM jasplakinolide. The contour of the ring before breaking is indicated with an orange dashed line. The orange and green arrows point at the site where the ring breaks and at the splayed fibers, respectively; see Video 3. Scale bars in B–F, 5 µm.