Otd and unpg form a common interface within the IZ. (a,b) Otd/En-lacZ double labelling. (c,d) unpg mRNA/En-lacZ double labelling in the peripheral head ectoderm (a,c) and deriving brain NBs at stage 11 (b,d). (b,d) Close-ups of regions framed in (a,c), respectively. (b) Note that Dd1 and Dv7 do not express Otd. (d) In the brain, unpg mRNA is detected in only two deutocerebral NBs (Dd1, Dv7) immediately anterior to the antennal en stripe (as) and bordering the Otd domain (b). (e) Summary of the expression of Otd, unpg, and En according to the colour code. Note the complementary expression of Otd and unpg, and that Dd1, Dv7 are part of the NBs of the IZ (IZ NBs). Red dashed lines indicate segmental borders. Other abbreviations are as in Figure 1.