Histochemical detection of pb and LacZ mRNA expression following in situ hybridization in embryos of the indicated genotypes and stages. (A–C). w1118 embryos at stage 11 (A), stage 12 (B), and stage 13 (C). (D–N) Region 2.1-deleted embryos, either as balanced heterozygotes identified by abdominal LacZ expression (D, F, H, J) or homozygotes lacking LacZ (E, G, I, K, L, M, N). (D,E) Ventral view of pb expression in maxillary and labial lobes (bracket) that is present in pb11D/TM3,Ubx-LacZ (D) and absent in pb11D/pb11D embryos at stage 9–10 (E), while expression in the hypopharyngeal lobe is similar for both genotypes (arrowhead). (F,G) By stage 11, expression in the maxillary and labial lobes (bracket) is detectable in both pb11D/TM3,Ubx-LacZ (F) and pb11D/pb11D (G) embryos, but visibly reduced in pb11D/pb11D (G). As in D,E, similar hypopharyngeal lobe expression is detectible in both genotypes (arrowhead). (H) Laterial view of stage 11 embryos, illustrating pb expression in pb11D/TM3,LacZ similar to w1118 (compare with A). (I) pb11D homozygous stage 11 embryos have detectable pb expression in the maxillary and labial lobes (see inset for higher magnificiation), but in a noticeably reduced territory. (J-N) Stage 12 pb11D/TM3,Ubx-LacZ embryos have pb expression comparable to w1118 (J, compare with B), while stage 12–13 pb11D homozygous embryo show similar reduction in expression area relative to w1118 and pb11D/TM3,Ubx-LacZ, (see also insets in K and M for zoom of maxillary and labial lobes, as well as Figure 5—figure supplement 4B,C). (O-U) Embryos from a double deletion of region 2.1 and EO053 (pb11E), either as balanced heterozygotes (O,Q), or homozygotes (P,R–U). Detection of pb mRNA in pb11E heterozygous embryos at stage 11 (O) or stage 12 (Q) is comparable to both w1118 (A,B) and pb11D/TM3,Ubx-LacZ (H,J; See also Figure 5—figure supplement 4A,D). (P) pb mRNA expression is noticeably reduced in stage 11 pb11E/pb11E homozygous embryos, while expression in the hyopharyngeal lobe is unaltered (inset). (R-U) Representative stage 12–13 pb11E/pb11E embryos also demonstrating reduced pb mRNA detection. Compare insets in R and T with K and M, respectively, and also refer to Figure 5—figure supplement 4E,F.