Microtubule assembly is not required to recruit SAS-4 to centrioles but is required for its stable incorporation during late prophase. (A) Kinetic profiles for recruitment of GFP:SAS-4 in embryos depleted of β-tubulin (tbb-1/2[RNAi]). Because tubulin-depleted embryos do not undergo cytokinesis, sequences were aligned relative to nuclear envelope breakdown, which occurs ∼257 s before cytokinesis onset in control embryos and with normal timing with respect to earlier events when microtubule assembly is inhibited (). (B) High-resolution images of control, tbb-1/2(RNAi), and sas-5,tbb-1/2 (RNAi) embryos expressing GFP:SAS-4, generated by mating as described in . Times (in seconds relative to nuclear envelope breakdown), correspond to meiosis (−1,364 to −1,099s), early (−940 to −873 s) and mid (−686 to −593 s) S phase, and late prophase/prometaphase (−27 to +94 s). Note that, although GFP:SAS-4 is not enriched at centrioles in SAS-5,TBB-1/2–depleted embryos, it still accumulates in the PCM (arrowhead). (C) Analysis of the central and peripheral GFP:SAS-4 signal in control, tbb-1/2(RNAi), and sas-5,tbb-1/2 (RNAi) embryos in prometaphase performed as in . Asterisks denote statistically significant differences relative to control (P < 0.05 by t test). (D) Two representative examples each of photobleached centrosomes in late prophase/prometaphase from control, tbb-1/2(RNAi), and sas-5,tbb-1/2(RNAi) embryos. Times are in seconds after photobleaching. All error bars indicate the 90% confidence interval. Bars, 5 μm.