Fig. 8. Model for the dynamic regulation of Br by EGFR and Dpp pathways. (A) A revised model of Br regulation by EGFR and Dpp signaling. The rising phase of Br expression in the roof cells is due to a feedforward loop activated by EGFR signaling (blue). The shutdown of br expression in the roof cells is due to a negative-feedback loop (red), which is formed by Br and Dpp signaling. See text for details. (B) Schematic diagram of the spatial and temporal patterns of the main components in the model. See text for details.