Nuclear import of the homeodomain protein Extradenticle in response to Wg and Dpp signalling

IN Drosophila, Decapentaplegic (Dpp)(1) and Wingless (Wg)(2) are two secreted signalling proteins of the transforming growth factor (TGF)-beta and Wnt families, respectively. Although both are often required during development, only a few downstream components of these signalling pathways have been described. Here we present evidence that in the embryonic midgut both signalling pathways control the subcellular localization of the homeodomain protein encoded by the extradenticle (exd) gene. Exd protein is predominantly nuclear in endoderm cells close to Dpp- and Wg-secreting cells of the, visceral mesoderm, but is in the cytoplasm in more distant endoderm cells. Both dpp and log are required for the nuclear localization of Exd in the endoderm.