Fig. 7.
Loss of Xxylt enhances the activation of Notch by ectopic Delta. (A–D) Third instar wing imaginal discs from larvae raised at 25°C. Staining with α-Cut and α-Delta antibodies are shown in red and green, respectively. Anterior is to the left, and dorsal is up. Scale bar in (A) is 50 μm and applies to all panels. (A-A”) Expression of Cut upon Delta overexpression using dpp-GAL4 (dpp > Dl) in a wild-type background. Arrows and the arrowhead indicate trans-activation and cis-inhibition, respectively. (B-B”) Loss of one copy of Xxylt does not alter the Cut expression pattern in a dpp > Dl wing disc. (C-C”) In an XxyltΔcds/Δcds background, dpp > Dl induces ectopic activation of Cut anterior to the Dpp domain (yellow arrowhead). (D-D”) In a shams heterozygous background, dpp > Dl results in ectopic activation of cut comparable to dpp > Dl in an XxyltΔcds/Δcds background (yellow arrowhead). Note that in both C and D, some cells at the anterior border of the dpp expression domain co-express Cut with low levels of Delta, likely because the Delta level in these cells is not sufficient to cis-inhibit Notch (insets).