Fig. 4. PHA-4 expression in wild-type and tbx-37 tbx-38 embryos. Wild-type and tbx-37 tbx-38 embryos are shown in the top and bottom rows, respectively. (A,E) PHA-4::GFP expression at morphogenesis stages as shown and labeled in Fig. 3A,B. PHA-4 is present at high levels in all of the pharyngeal nuclei (brackets) and rectal nuclei (left of arrowhead in each panel), and present at lower levels in the intestinal nuclei. (B,F) Light micrographs of living embryos just prior to morphogenesis; the daughters of the MS cell were killed during early embryogenesis. (C,G) PHA-4::GFP expression in the embryos shown in B and F, respectively. In the wild-type embryo (B,C), cells in the anterior pharyngeal primordium (ant) and the intestinal cells express GFP, but the posterior pharyngeal primordium (pos) has not formed. In the tbx-37 tbx-38 embryo (F,G), no pharyngeal cells are present. (D,H) PHA-4::GFP expression in 44-cell embryos. Both embryos show PHA-4::GFP in the MS granddaughters (top 4 GFP-positive nuclei) but only the wild-type embryo expresses PHA-4::GFP in ABa descendants (arrows indicate ABaraaa and ABarapa).