Dl is expressed throughout the wing primordium of early third instar wing imaginal discs.

<p>(A–C) Expression of Dl in an early third instar wing imaginal disc that express UAS <i>fng</i> with <i>ptc</i>Gal4. (A) Expression of Dl in a disc without clones. Expression in enhanced at the D/V boundary and the ectopic FB (arrow). (B, C) Expression of Dl in a disc bearing <i>Dl^rev10</i> mutant clones. (B) The clones are labelled by the absence of GFP (arrowh in B, C). The arrowhead highlights a clone with cells homozygous for GFP and the Dl wildtype allele (GFP/GFP). (C) Expression of Dl in the same disc as in (B). The comparison of (B) and (C) reveals that the staining is strongly reduced in <i>Dl^rev10</i> mutant clones and enhanced in cell clones homozygous for the wildtype allele. (D–I) Asymmetric Notch signalling at the D/V boundary. (D–G) Expression of Wg and Ap in an early third larval instar wing imaginal disc. (F, G) is a magnification of the D/V region of the disc shown in (D, E). The domain of Wg along the D/V boundary is largely restricted to ventral boundary cells adjacent to the Ap domain (see merge in D). (H, I) In late stages Wg is expressed also in DBCs. However, while it is restricted to DBCs (arrowhead in I), it is expressed in VBCs and the adjacent row of ventral cells (arrows in I).