Anterior and posterior compartments in the proboscis of Drosophila.

Genetic techniques for marking single cells and their descendents are used to study the development of the Drosophila proboscis. The proboscis develops from a pair of imaginal discs which form the left and right halves of the adult organ. Each half of the proboscis is subdivided into two compartments, one positioned anterior to the other. The homeotic mutation proboscipedia transforms the distal proboscis into a pair of distal first legs or antennae. Clones of this mutation are restricted to one or the other of the two proboscis compartments and reveal a precise homology between these compartments and the anterior and posterior compartments of the thorax and eye-antenna. These results provide strong support for the hypothesis that anterior and posterior compartments reflect basic subunits of segment development in Drosophila.