A DPP-mediated feed-forward loop canalizes morphogenesis during Drosophila dorsal closure.

Development is robust because nature has selected various mechanisms to buffer the deleterious effects of environmental and genetic variations to deliver phenotypic stability. Robustness relies on smart network motifs such as feed-forward loops (FFLs) that ensure the reliable interpretation of developmental signals. In this paper, we show that Decapentaplegic (DPP) and JNK form a coherent FFL that controls the specification and differentiation of leading edge cells during Drosophila melanogaster dorsal closure (DC). We provide molecular evidence that through repression by Brinker (Brk), the DPP branch of the FFL filters unwanted JNK activity. Highthroughput live imaging revealed that this DPP/Brk branch is dispensable for DC under normal conditions but is required when embryos are subjected to thermal stress. Our results indicate that the wiring of DPP signaling buffers against environmental challenges and canalizes cell identity. We propose that the main function of DPP pathway during Drosophila DC is to ensure robust morphogenesis, a distinct function from its well-established ability to spread spatial information.