Figure 7. Expression of a
pha-1:lacZ hybrid protein during embryogenesis. (A-J) Immunofluorescence of
pha-1:lacZ expressing embryos of different stages double stained with anti-beta-galactosidase (left column) and cell type-specific antibodies (right column). All embryos are arranged with the anterior to the left. (A) Expression of the
pha-1:lacZ hybrid protein is first detectable at about 130 minutes of embryonic development in some cells that have positions similar to descendants of the pharynx producing blastomere MS and AB (arrowheads) and all body wall muscle cell precursors at the posterior pole (arrows). (B) Staining of the same embryo with the myoD-specific antiserum HM-1. The arrows point towards cells that express the
pha-1:lacZ hybrid and the myoD protein, indicating that these cells are the body wall muscle cell precursors. (C) Around 200 minutes of embryonic development the
pha-1:lacZ protein is expressed in pharyngeal precursors at the anterior pole of the embryo and in body wall muscle cell precursors that form a U-shaped structure in the posterior half of the embryo. The beta-galactosidase-positive cells at the anterior pole of the embryo have positions similar to the pharyngeal precursors present at that time of development. (D) Positions of the AB- or MS-derived pharyngeal precursors that will contribute to pharyngeal cells (open circles) and C- and D-derived myoblasts (filled circles; adopted from Sulston, 1983). At this time of development 26 pharyngeal precursors are present in the embryo that will contribute to 77 of the 80 embryonic pharyngeal cells (Fig. 8). (E,F) Embryo of the same stage as in C, stained with a monoclonal antibody against beta-galactosidase (E) and with the 48C7 antibody thatstains pharyngeal precursors (F). (G,H) Embryo at about 400 minutes of embryonic development stained with a monoclonal antibody against beta-galactosidase (G) and withthe HM-1 The
pha-1:lacZ hybrid protein (G) is still expressed in the body wall muscle cell precursors. (H) Few cells in the presumptive pharynx region express the hybrid protein (not shown). (I,J) Embryo at 450 minutes, shortly after morphogenesis has started, stained with a monoclonal antibody against beta-galactosidase (I) and with the 3NB12antibody that stains pharyngeal precursors (J). No expression of the
pha-1 hybrid protein is detectable in the pharyngeal cells. (K-N) Analysis of body wall muscle differentiation in
pha-1 mutants. Embryo mutant for the allele
e2123ts raised at the nonpermissive temperature. (K) Normarski micrograph of the embryo. The arrows point at the undifferentiated pharynx primordium. (L) Immunofluorescence micrograph of the embryo. The body wall muscle is differentiated normally in the embryo (mAb NE8 4C6.3; see Schnabel (1994) for a description of the antibody). (M-N) Two focal layers of an embryo that is homozygous for a small deficiency tDf2 deleting the
pha-1 gene (Schnabel and Schnabel, 1990). The staining with the mAb NE8 4C6.3 shows that the body wall muscle has differentiated normally in the absence of
pha-1 activity. Bar, 10 µm.