Automorphy as a self-organizing DPP-dependent process that translates patterns into mechanical programs during Drosophila embryogenesis

Morphogens provide developing tissues with positional information to ensure coherent morphogenesis. Bone morphogenetic proteins (BMPs) initially form a gradient to pattern the dorsal domains of the Drosophila embryo. Here, we show that the BMP homolog decapentaplegic (DPP) endows dorsal domains with specific mechanical programs to organize morphogenesis. These domains self-organize using high local DPP activities, a process we call automorphy. Automorphy is key to inducing specific morphological changes while being faithful to the initial positional information. The BMP morphogen therefore uses a series of automorphic events to translate each position into physical potentials that later produce a contractile amnioserosa and a dorsal epidermis displaying plasticity. Plasticity allows cell elongation in wild-type embryos, and perturbations of cellular patterns reveal its crucial role in adapting to mechanical constraints. We propose that gradient formation and automorphy constitute complementary processes that allow BMPs to act as a morphogen in the Drosophila embryo.