Fig. 5. Dorsal closure is blocked by prddisco expression. (A) In wild-type stage 13 embryos, note the dorsoventral stripes of EN marking the posterior compartment of each segment. (B) In prddisco embryos the segments expressing disco do not complete dorsal closure. The EN stripes in these segments extend only about halfway up the embryo. Note that the affected segments are curved and resemble the gnathal lobes. (C-D) pnr mRNA distribution in prddisco embryos. (C) In early stage 12 wild-type embryos, pnr mRNA accumulates along the dorsal edge of the segments, beginning in the posterior maxillary and extending posteriorly through the eighth abdominal segment. (D) In prddisco embryos, this continuous line of pnr mRNA is disrupted. Cells expressing prddisco do not accumulate pnr. (E-G) disco expression limits the gnathal contribution to the dorsal ridge. (E) Morphology of a normal wild-type stage 13 dorsal ridge. Note the separation of the dorsal ridge from the labial lobe, from which many of the dorsal ridge cells arise. (F) In embryos expressing prddisco, the dorsal ridge is quite reduced. The few EN-positive cells remaining are those that arise from the posterior maxillary/anterior labial where prddisco is not expressed. (G) In Df(1)XR14/Y embryos, the dorsal ridge is broadened and contiguous with labial, and sometimes as in this case, maxillary lobes. The embryos were stained to detect EN to facilitate identification of prddisco embryos. dr, dorsal ridge. Anterior is towards the left; dorsal is upwards.