Maintaining ribosomal DNA (rDNA) copy number is vital for germline integrity. In Drosophila, rDNA expansion relies on R2 retrotransposon-induced DNA breaks. A new paper from the lab identifies the insulin receptor (InR) as a key repressor of R2, preventing unnecessary damage. When rDNA CN is low, male germline stem cells reduce InR expression, activating R2 and promoting CN expansion. Dietary changes also modulate this pathway, suggesting insulin signaling connects environmental cues to heritable genomic regulation.