Myc and Tor drive growth and cell competition in the regeneration blastema of Drosophila wing imaginal discs.

During the regeneration of injured or lost tissues, the regeneration blastema serves as a hub for robust growth. Drosophila imaginal discs are a genetically tractable and simple model system for the study of regeneration and organization of this regrowth. Key signals that contribute to regenerative growth in these discs, such as reactive oxygen species, Wnt/Wg, JNK, p38, JAK/STAT and the Hippo pathway, have been identified. However, a detailed exploration of the spatial organization of regrowth, the factors that directly drive this growth, and the consequences of activating drivers of regeneration has not been undertaken. Here, we find that regenerative growth in imaginal discs is controlled by the transcription factor Myc and by Tor signaling, which drive proliferation and translation in the regeneration blastema. The spatial organization of growth in the blastema is arranged into concentric growth zones defined by Myc expression, elevated Tor activity and elevated translation. In addition, the increased Myc expression in the innermost zone induced Xrp1-independent cell competition-like death in the adjacent zones, revealing a delicate balance between driving growth and inducing death in the regenerating tissue.