Significance: The yellow, orange, and red colors of birds are produced through the deposition of carotenoid pigments into feathers and skin, and often function as signals in aggressive interactions and mate choice. These colors are hypothesized to communicate information about individual quality because their expression is linked to vital cellular processes through the mechanisms of carotenoid metabolism. To elucidate these mechanisms, we carried out genomic and biochemical analyses of the white recessive canary breed, which carries a heritable defect in carotenoid uptake. We identified a mutation in theSCARB1gene in this breed that disrupts carotenoid transport function. Our study implicates SCARB1 as a key mediator of carotenoid-based coloration and suggests a link between carotenoid coloration and lipid metabolism.

Canaries changing colors: Many animals are sexually dimorphic, with different phenotypes in males and females. To identify the genetic basis of sexual differences in bird coloration, Gazda et al. investigated red coloration in mosaic canaries and related species (see the Perspective by Chen). Using a combination of genetic crosses, genomic mapping, transcriptomics, and comparative analyses, the authors show that trans-regulation of the carotenoid-processing gene BCO2 is involved in sexual dichromatism. Although such variation in coloration among the sexes is common, particularly in birds, there are few candidate genes known to be involved. This study helps to elucidate the molecular mechanisms that underlie the evolution of dichromatism and may aid in uncovering sexually selected traits. Science , this issue p. 1270 ; see also p. 1185