Fig. 8. A model for the regionalization of AbdA activity: cis-regulatory readouts of a Hox/signaling combinatorial code subdivide the domain of AbdA protein function. Simultaneous requirement of Dpp signaling and AbdA results in localized wg transcriptional activation in PS8 VM cells. The direct convergence of AbdA and Dpp signaling on a wg cis-regulatory region has been established in this study. The model hypothesizes that the regulation of pnt and opa also results from direct cis-regulatory integration of Hox and signaling inputs. In the regulation of pnt, Wg-activated transcription factors synergise with AbdA, ultimately resulting in localized (PS8-10) transcription of pnt. In the regulation of opa that only occurs in the absence of Dpp signaling, Dpp-activated regulators inhibit opa activation through AbdA. According to this model, the cis-regulatory readout of a Hox/signaling combinatorial code is instructive in the regionalization of AbdA transcriptional activity, and thus confers functional diversity to AbdA. WRE, Wg response element; DRE, Dpp response element; HRE, Hox response element.