Fig. 1. Homo-dimerisation of DOME as detected by the ßlue-ßlau technique. (A) Wild-type posterior spiracles with an elongated filzkörper (arrow). (B) Zygotic phenotype of dome²¹⁷, the filzkörper is not formed. (C) Rescue of dome²¹⁷ with UAS-dome. Expression of the hybrid receptor in the spiracles using Klu-Gal4 rescues the filzkörper, showing that the hybrid protein is functional. Optical sections through the salivary gland (D,F,H) and the hindgut (E,G,I). White arrowheads point to the apical membrane, black arrowheads to the basal membrane on one side of the tube. Note that the salivary gland is closed at one end whereas the gut tube is open at both ends. (D-E) Anti-ß-gal staining of UAS-dome, UAS-dome expressed using h-Gal4. The hybrid receptors localise mainly to the apical membrane, although the proteins are also detected in the cytoplasm. (F-G) X-gal staining of the same genotype as in D-E. The blue precipitate is formed at the apical side of the cell in both the salivary glands and the hindgut showing that the product of the reaction has a limited diffusion through the cell. (H-I) X-gal staining of UAS-dome expressed using h-Gal4. No coloured precipitate is seen when only one of the two fusion proteins is expressed, proving that the reaction requires complementation of the hybrid receptors.