Filling in the gaps In a plant seed, the embryo lies dormant surrounded by nutritive endosperm while awaiting suitable conditions to germinate. A hydrophobic cuticle around the embryo protects it from catastrophic water loss during the early days of growth. Doll et al. identified a back-and-forth signaling pathway that ensures an intact cuticle. The precursor of a signaling peptide is made in the embryo and transferred to the endosperm, where it is processed into an active form. The activated peptide diffuses back into the embryo to activate receptor-like kinases that drive cuticle development. Serve and return continues until all leaks in the cuticle are filled in and the peptide can no longer cross the barrier. Science , this issue p. 431