Gastrulation phenotypes in embryos and lip explants. (A and A′) WT and Pk1-MO embryos at early gastrulation. Scale bars, 100 μm. (A′′) Gastrulation is rescued by Pk1 mRNA. Scale bar, 100 μm. (B and B′) Dorsal blastopore lip explants indicated movement defects after Pk1 knockdown. Scale bars, 100 μm. (C) Fractions showing involution of WT, Pk1-MO, and rescued embryos. n, number of embryos.