Cell interaction between compartments establishes the proximal-distal axis of Drosophila legs

Abstract

THE appendage primordia of Drosophila are subdivided into compartments^1–4 by the localized expression of transcription factors^5–7. Interaction between cells in adjacent compartments establishes organizing centres responsible for generating spatial pattern and promoting cell proliferation in the developing appendages^7–9. Localized expression of hedgehog (hh) in the pos-terior compartment of the leg imaginal disc directs expression of wingless (wg) in ventral–anterior cells and decapentaplegic (dpp) in dorsal–anterior cells near the anterior–posterior compartment boundary⁸; wg then acts to specify ventral cell fate^10–12 and to organize the dorsal–ventral axis of the leg^13,14. Interaction between wg-expressing ventral cells and dorsal cells near the anterior–posterior compartment boundary promotes axis formation in the leg^14,15. Here we show that the combined action of wg-expressing cells in the ventral–anterior compartment and dpp-expressing cells in the dorsal–anterior compartment activates expression of Distalless, a gene required for proximal–distal axis formation in the limbs. These results demonstrate that sequential interaction between anterior–posterior and dorsal–ventral compartments establishes the proximal–distal axis of the limbs.