The Spatiotemporal Limits of Developmental Erk Signaling

Abstract

Animal development is characterized by signaling events that occur at precise locations and times within the embryo, yet determining when and where such precision is needed for proper embryogenesis has been a longstanding challenge. Here we address this question for Erk signaling, a key developmental patterning cue. We describe an optogenetic system for activating Erk with high spatiotemporal precision in vivo. Implementing this system in Drosophila, we find that embryogenesis is remarkably robust to ectopic Erk signaling, except from 1 to 4 hours post fertilization when perturbing the spatial extent of Erk pathway activation leads to dramatic disruptions of patterning and morphogenesis. Later in development, the effects of ectopic signaling are buffered, at least in part by combinatorial mechanisms. Our approach can be used to systematically probe the differential contributions of the Erk pathway and concurrent signals, leading to a more quantitative understanding of developmental signaling.