Asymmetric requirement of Dpp/BMP morphogen dispersal in the Drosophila wing disc

Morphogen gradients provide positional information and control growth in developing tissues, but the 24 underlying mechanisms remain largely unknown due to lack of tools manipulating morphogen 25 gradients. Here, we generate two synthetic protein binder tools manipulating different parameters of 26 Decapentaplegic (Dpp), a morphogen thought to control Drosophila wing disc patterning and growth 27 by dispersal; while HA trap blocks Dpp dispersal, Dpp trap blocks Dpp dispersal and signaling in the 28 source cells. Using these tools, we found that while posterior patterning and growth require Dpp 29 dispersal, anterior patterning and growth largely proceed without Dpp dispersal. We show that dpp 30 transcriptional refinement from an initially uniform to a localized expression and persistent signaling 31 in transient dpp source cells render the anterior compartment robust to blocking Dpp dispersal. 32 Furthermore, neither Dpp dispersal nor signaling is critical for lateral wing growth. These results 33 challenge Dpp dispersal-centric mechanisms, and demonstrate the utility of customized protein binder 34 tools to dissect protein functions.