Modulation of Avian Iridescence via Malanogenesis

AO_SCPLOWBSTRACTC_SCPLOWThe iridescent colors of birds originate in nanoscale feather structures that interact with light. Although the physical principles governing avian iridescence are well-established, the molecular mechanisms assembling these nanostructures into photonic materials remain unknown. Here, we investigate the genetic and developmental basis of iridescence by analyzing mutations from peafowl domestication and color variation in wild birds. We show that melanogenesis governs diverse geometric aspects of feather photonic nanostructures, enabling gains, shifts, and losses in iridescence. Mutations altering melanin composition collapse multilayered photonic systems and yield non-iridescent tissues, while alterations to melanosome abundance, elongation, or deposition timing generate multilayer architectures of variable periodicity and striking color differences. Notably, transitions from non-iridescent to iridescent plumage can arise from single-nucleotide mutations in melanogenic genes, revealing that minimal genetic change can prompt feathers to organize photonic structures. These results demonstrate that the nanoscale order underlying iridescence is developmentally plastic, emerging from physicochemical self-assembly responsive to the biochemical environment rather than from genetically encoded spatial cues. Single-cell transcriptomes from wild species further uncovered extensive melanocyte-centered regulatory rewiring associated with iridescence. Our findings identify melanogenesis as a key pathway for evolving structural coloration and illustrate how genetic programs harness self-organizing processes to generate biological diversity.