Fig. 2. Co-expression of dpp and Dl can induce neural differentiation in all regions ahead of the morphogenetic furrow. The white arrows indicate the approximate position of the morphogenetic furrow. (A) Induction of neural differentiation (visualised by Elav expression in red) in clones ectopically expressing Dl alone (green) is limited to a band of cells near of the morphogenetic furrow (arrowhead). (B-F) Clones ectopically expressing Dl and dpp (green). (B,C) Clones co-expressing dpp and Dl can trigger neural differentiation in all regions anterior to the morphogenetic furrow, even in clones far from the morphogenetic furrow (arrowhead); compare with A. (D-F) The first effect caused by these double overexpressing clones is the activation of Atonal (red). Again, this induction occurs in all the cells surrounding the clone even when they are distant from the competent region. In most cases, Atonal expression is observed several cells away from the border of the clone; within the clone, only isolated cells express Atonal. We explain this result as the consequence of the Atonal expression inducing an ectopic morphogenetic furrow (see text).
