Fig. 5. Expression of Dl, the SOP-E and E(spl)m8-lacZ in Su(H)⁴⁷ mutant wing imaginal disc of the late third larval instar stage. Anterior is towards the left, ventral towards the bottom. (A) Expression of Dl, revealed by anti Dl antibody staining, is elevated in the cells of the proneural clusters (highlighted by the arrows). (B) Expression of the SOP-E in Su(H)⁴⁷ mutant discs indicates that most of the cells of the proneural clusters express this enhancer (arrows). (C) The same Su(H)⁴⁷ mutant wing disc as shown in A and B showing expression of Dl (red) and anti ß-Gal antibody (green) to visualize the expression of E(spl)m8. Expression of E(spl)m8-lacZ is detectable in the cells of the proneural clusters. (D,E) Expression of E(spl)m8-lacZ in the notal region of a wild-type wing imaginal discs. (D) Expression of E(spl)m8-lacZ, (E) Expression of Sens (red) and E(spl)m8-lacZ (green). The comparison between D and E reveals that expression of E(spl)m8-lacZ is switched off in SOPs at the time when they initiate expression of Sens (Nolo et al., 2000). The arrows in D and E indicate the developing SOPs. (F) Results summary. Cells of the proneural cluster in Su(H) mutant notae are present but arrest their development before expression of sens and hnt is initiated.