Curvature gradient drives polarized tissue flow in the <i>Drosophila</i> embryo

Significance Much is known about how genetic prepatterning of the embryo defines the initial instructions for morphogenesis, but how these instructions are deployed in a specific mechanical and geometrical environment is unknown. In our manuscript, we use Drosophila embryos to explore how genetics, mechanics, and geometry interact to drive polarized (directional) tissue flow. Through a combination of experimental and modeling approaches, we show that previously proposed mechanisms cannot account for the tissue flows observed during the early stages of Drosophila morphogenesis. Instead, we reveal a mechanism whereby polarized flows arise from the interaction between myosindriven tissue contraction and the curvature of the tissue imposed by the shape of the egg