Figure 4

Loss of emb-8 or pod-2 impairs cortical interaction by the paternal pronucleus which correlates with loss of polarity. Representative wild-type (A-D), emb-8(RNAi) (E-H), and pod-2(ye60) embryos (I-L). In wild type, (A) the paternal pronucleus initially appears in the posterior cytoplasm and (B) moves to the posterior where it closely associates with the cortex. This cortical interaction is maintained for approximately 5 minutes before (C) the pronucleus dissociates and (D) migrates to meet the maternal pronucleus in the posterior cytoplasm. In 8/16 emb-8(RNAi) embryos, (E) the paternal pronucleus appears in the posterior cytoplasm and some posterior movement occurs; however (F-G) contact with the cortex is not made and (H) the paternal and maternal pronuclei meet near the center of the embryo. In pod-2(ye60) mutants, (I-K) the paternal pronucleus does not become juxtaposed with the cortex. Subsequently, (L) the pronuclei meet in the center of the embryo. (M) Correlation between impaired cortical interaction and symmetric division in emb-8(RNAi) embryos. Relative size of the anterior blastomere (cross-sectional area) of individual embryos is indicated on the y-axis. Duration of pronucleus-cortex interaction is indicated along the x-axis. For 8 embryos, no interaction occurred ("no contact"). Symmetric division was defined as two-cell embryos in which the anterior blastomere comprised less than 53% of the total area. Blue bars = symmetric division. Red bars = asymmetric division.