Figure 2.

Relationship among tsh, ey, so, and dac. (A and B) Expression of ey/lacZ in wild-type and Four eyes eye-antenna discs, respectively. Ectopic ey expression is observed at the ventral region of the antennal disc in Four eyes (marked with asterisk). (C and D) Expression of tsh in wild-type flies and flies of genotype UAS:ey × dpp GAL4, respectively. tsh expression was monitored with a P element enhancer trap tsh allele, tsh¹. tsh is normally expressed only in the eye portion of the eye-antenna disc. Its expression is strongly induced in the ventral antennal region in flies bearing UAS:ey and dpp-GAL4 (marked with asterisk). (E and F) Expression of so in wild-type and Four eyes eye-antenna discs, respectively. so expression was monitored using a P element enhancer trap allele, so⁷. Ectopic so expression is observed at the ventral region of the antennal disc in Four eyes (marked with asterisk). (G and H) Expression of dac in wild-type and Four eyes eye-antenna discs, respectively. dac expression was monitored using a P element enhancer trap dac allele, dac^P. Ectopic dac expression is observed at the ventral region of the antennal disc in Four eyes (marked with asterisk). (I) Expression pattern of tsh in the eye antenna disc as revealed by RNA in situ hybridization. Note that tsh is most strongly expressed anteriorly to the morphogenetic furrow (arrowhead). The tsh/lacZ expression in G and H extends more posteriorly, presumably because of the perdurance of β-galactosidase. (J) Normal ommatidial development in tsh mutant clones. Shown is a section through an adult eye containing a w⁻ clone that is homozygous for a null tsh allele, tsh⁸. The mutant clone, which is located to the left, is recognizable by the lack of pigment granules. Note that the mutant ommatidia show normal number and organization of photoreceptors and accessory cells.