Ordered degradation of APC/C substrates in oocyte meiosis I. (A and B) Cyclin B3 was degraded after securin or cyclin A2. mRNA encoding cyclin B3–RFP and either securin-YFP (A; 20 oocytes) or cyclin A2–GFP (B; 19 oocytes) were coinjected into GV oocytes of CD-1 mice. Each panel shows selected frames from a video of a representative oocyte, with an overlay of DIC and RFP channels in the top rows, and DIC and YFP or GFP channels in the bottom rows. (C) The D box of cyclin B3 is required for degradation. CD-1 GV oocytes (10 oocytes) were injected with mRNA encoding cyclin B3–RFP with the D box deleted (ΔDbox). Frames from a representative video are shown, with the DIC channel on top and RFP at the bottom. All panels: Time points after GVBD (BD) are indicated as hours:minutes. Scale bars, 20 µm. White asterisks: PBs. Quantification of fluorescence intensities is shown on the right (mean ± SD of the indicated number of oocytes from three independent experiments).