Integrating Hox and signaling pathways during Drosophila posterior spiracle development. S. Merabet , J. Pradel , Y. Graba. Campus Luminy, CNRS/LGPD, Marseille Provenc, France.

   The functions of Hox proteins and signaling pathways during development have been individually extensively studied. How they act together to specify morphogenetic events is however poorly understood. Most of the interactions described so far relie on cross-regulatory interactions. We used posterior spiracle development as a model system to study the contribution and interaction of both developmental regulators to morphogenesis. The Drosophila posterior spiracle is built of two structures, an internal one called the filzkorper, and an external dome shaped structure, the stigmatophore, both requiring AbdominalB (AbdB) function. We studied in details the spatio-temporal expression and requirement of three signaling pathways, Wingless Hedgehog and EGF, to filzkorper and stigmatophore morphogenesis. We found that they provide distinct signaling sources that are required for normal flizkorper and stigmatophore development. Epistasis experiments further show that all three signaling pathway apparently independently contribute to both morphogenetic processes. Similar experiments are conducted to assess whether these signaling pathways are required upstream or downstream of AbdB. Preliminary observations suggest that, in most cases, the signaling pathway act downstream of AbdB. In summary, we show that several signaling pathways distinctly contribute to AbdB controlled posterior spiracle specification, in a manner that does not necessarily involve cross regulation between Hox and signaling pathways.