Expression pattern of pb in embryos. (A–D) stage 11 embryos, (E–H) stage 17 embryos. (A,E) D. melanogaster,(B,F) D. virilis,(C,G) D. buzzatii, and (D,H) D. repleta. (A–D) Expression on the ectoderm of the maxillary and labial lobes. Later in development (E–H) pb is detected in the derivatives of the maxillary (white arrowhead) and labial (black arrowhead) lobes, and in the ventral nervous system (boxed area). (A–D) pb expression is detected in the mesodermal layer of the mandibular segment (black arrow) in all four species. In D. virilis only (B), pb is also expressed in the mesodermal layer of the maxillary segment (white arrow). The mandibular (mn), maxillary (mx), and labial (lab) segments are shown in A.
