Induction of a mirror-image duplication of anterior wing structures by localized hedgehog expression in the anterior compartment of Drosophila melanogaster wing imaginal discs

Abstract

The segment polarity gene hedgehog (hh) encodes a secretory protein involved in cell-cell communication in Drosophila melanogaster. The hh gene is expressed in the posterior compartment and is essential for the establishment and maintenance of the anterior/posterior-compartment boundary of each embryonic parasegment [Ingham, P.W., Nature 366 (1993) 560-562]. To clarify possible hh functions in adult appendage formation, we isolated a fly line (h9D) associated with a wing malformation from among fly lines with an hh transgene whose expression is under the control of trapped enhancers. In h9D flies, the ectopic expression of hh occurred in the anterior edge of wing pouch in the wing disc. This abnormal hh expression resulted in not only a mirror-image duplication and ectopic outgrowth in the anterior wing compartment, but also the ectopic expression of patched and decapentaplegic, strongly suggesting that the hh product serves as a morphogen or an inducer essential for wing development, including the proximal/distal axis formation.