Fig. 5. Toy- and temperature-dependent transcription of ey in the eye-antennal anlagen. A-F are dorsal views of the same embryos focused in two different horizontal planes on ey transcripts in the eye-antennal primordia (left) or the CNS (right). (A-H) Transcription of ey in the eye-antennal primordia depends on Toy and temperature. Transcript levels of the ey gene, assayed by in situ hybridization with a DIG-labeled antisense RNA probe extending from exon 3 to 9 of the ey gene, in late stage 16 embryos derived from toy^hdl/l(4)2C2 (A-F), or Df(4)spa⁶⁶/ci^D spa^pol parents (G,H) are normal in the eye-antennal primordia (EAD) of embryos with one or two wild-type copies of the toy gene (A,B), but clearly reduced in those of homozygous toy^hdl (C-F) and Df(4)spa⁶⁶ (G,H) embryos at 25°C (C,D,G) and 18°C (E,F,H). (I,J) Ectopic ey transcripts in homozygous or heterozygous ey^D embryos. Transcripts of the ey^D gene, detected by in situ hybridization of a probe specific for exons 1-5 of the ey gene, are shown in two different horizontal focal planes as ventral views of a late stage 16 embryo at 18°C derived from ey^D/l(4)2C2 parents. 18 out of 120 late stage 16 embryos developing at 25°C, and 9 out of 63 such embryos at 18°C showed strong ectopic expression of ey transcripts as in J.

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