Localization of blt mRNA determined by in situ RT-PCR (A, B) and in situ hybridization with a digoxigenin-labeled blt riboprobe (C-H). In stage 8–11 embryos, specific staining was observed in the neuroectoderm (nec) and in the invaginating pole cells (pc) (A). In stage 15–16 embryos, specific staining appears in the developing central nervous system (CNS) (B). In the third instar larvae, blt mRNA is localized in neuromuscular junctions (C and D; arrows), and in the ring gland (RG) (E). (F-H) In adult flies, panel F shows blt mRNA localization in the interneurons of the optic lobe (arrowheads) and in the large cells (arrows), panel G shows specific staining in the corpus allatum (CA) and panel H, in the ovary.