Meeting Abstract
One of the best-studied ornamental traits is carotenoid-based coloration. In many bird species, red coloration is a criterion in female mate choice with females choosing males with red-shifted as opposed to yellow-shifted hue. Few bird species ingest red carotenoid pigments. To produce red feather coloration, most birds ingest yellow carotenoid pigments and biochemically convert them to red ornamental pigments via an oxidation reaction catalyzed by a previously unknown ketolase. In an effort to identify the ketolase, we conducted a comparative genomic study of the common canary (Serinus canaria) which has only yellow feather coloration, the red siskin (Spinus cucullata) which has red feather coloration, and the “red factor” canary which is a hybrid taxon with red feather coloration produced by crossing common canaries with red siskins. Using whole-genome sequencing, we identified two genomic regions introgressed from red siskins into red factor canaries that are required for red coloration. One of these regions contains a gene encoding a cytochrome P450 enzyme, CYP2J19, which is very likely the ketolase that enables yellow-to-red conversion of carotenoids. Transcriptomic analysis demonstrates that CYP2J19 is significantly upregulated in the skin and liver of red factor canaries and that it is also upregulated in the retina where red carotenoid pigments are also produced. The second introgressed region required for red feathers resides within the epidermal differentiation complex, and we speculate that this gene plays a key role in the incorporation of carotenoid pigments into growing feathers. The discovery of the gene responsible for red carotenoid coloration in birds has important implications for understanding the evolution of ornamental traits and female mating preferences.
