DPP CONTROLS TRACHEAL CELL-MIGRATION ALONG THE DORSOVENTRAL BODY AXISOF THE DROSOPHILA EMBRYO

We report that DPP signaling is required for directed tracheal cell mi gration during Drosophila embryogenesis. The failure of tracheal cells to receive the DPP signal from adjacent dorsal and ventral cells resu lts in the absence of dorsal and ventral migrations. Ectopic DPP signa ling can reprogram cells in the center of the placode to adopt a dorso ventral migration behavior. The effects observed in response to ectopi c DPP signaling are also observed upon the tracheal-specific expressio n of a constitutive active DPP type I receptor (TKVQ253D), indicating that the DPP signal is received and transmitted in tracheal cells to c ontrol their migration behavior, DPP signaling determines localized ge ne expression patterns in the developing tracheal placode, and is also required for the dorsal expression of the recently identified BRANCHL ESS (BNL) guidance molecule, the ligand of the BREATHLESS (BTL) recept or. Thus, DPP plays a dual role during tracheal cell migration, It is required to control the dorsal expression of the BNL ligand; in additi on, the DPP signal recruits groups of dorsal and ventral tracheal cell s and programs them to migrate in dorsal and ventral directions.