Fig. 8. Early activation of the EGFR/Ras transduction pathway is sufficient to generate an ectopic D compartment. (A-C) Wing imaginal discs containing clones of cells ectopically expressing either EGFR (A), Ras^V12 (B) or Rho (C), monitored for ap-lacZ (A, red), Ap (B,C, red), Wg (A, blue) or mirr-lacZ (C, blue) expression. Clones were induced during first (A,B) or late second/early third larval instar (C), and are marked either by absence (A,C) or presence (B) of GFP expression. Cells expressing both Ap (or ap-lacZ) and GFP appear yellow. (A) EGFR-expressing cells can form an ectopic D compartment within the V compartment. Note that only some cells within the clone express ap-lacZ and form the ectopic D compartment, and that the ectopic D compartment is encircled by a stripe of Wg-expressing cells that flank the ectopic DV boundary. (B) Early-induced Ras^V12-expressing clones autonomously express ap and form an ectopic D compartment. (C) Late-induced Rho-expressing clones fail to induce ectopic Ap expression, but still retain the ability of inducing ectopic mirr-lacZ expression within the presumptive wing hinge.

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