Fig. 1. Reporter gene expression pattern of the kropf^P188 line and location of the P insertions in the innexin 2 transcription unit. (A-F) ß-Gal expression monitored by anti-ß-Gal antibody staining of whole-mount embryos. (A) Stage 10 embryo, showing uniform expression in the germ band (arrow). With the beginning of germ band retraction (B), the ubiquitous expression pattern resolves into localised expression in the ectodermal fore- and hindgut, the endodermal anterior and posterior midgut, and the excretory Malpighian tubule primordia. During germ band retraction, reporter gene expression is maintained in these tissues (C-E) and in stage 17 embryos (E,F), expression occurs predominantly in the endodermal parts of the proventriculus and in the small intestine in the hindgut. (G) The localisation of the P-element insertions is indicated by inverted triangles. The genomic organisation of the transcript is shown below (Stebbings et al., 2000). (H) In situ hybridisation analysis of wild type (H) and of a kropf mutant embryo (I) using antisense probes for innexin 2 (inx2) and orthopedia (otp; internal staining control). Note that the inx2 pattern is abolished in kropf mutants, whereas otp is still expressed. amg, anterior midgut; fg, foregut; hg, hindgut; MT, Malpighian tubules; pmg, posterior midgut; pv, proventriculus; si, small intestine.