Red ketocarotenoid pigmentation in the zebra finch is controlled by a cytochrome P450 gene cluster
Birkhead, Tim R
Elsevier (Cell Press)
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Mundy, N. I., Stapley, J., Bennison, C., Tucker, R., Twyman, H., Kim, K., Burke, T., et al. (2016). Red ketocarotenoid pigmentation in the zebra finch is controlled by a cytochrome P450 gene cluster. Current Biology, 26 1435-1440. https://doi.org/10.1016/j.cub.2016.04.047
Bright red colours in vertebrates are commonly involved in sexual, social and interspecific signalling [1-8], and are largely produced by keto-carotenoid pigments. In landbirds, keto-carotenoids such as astaxanthin are usually metabolically derived via ketolation of dietary yellow carotenoids [9-10]. However, the molecular basis of this gene-environment mechanism has remained obscure. Here we use the yellowbeak mutation in zebra finch (Taenopygia guttata) to investigate the genetic basis of red coloration. Wildtype keto-carotenoids were absent in the beak and tarsus of yellowbeak birds. The yellowbeak mutation mapped to chromosome 8, close to a cluster of cytochrome P450 loci (CYP2J2-like) that are candidates for carotenoid ketolases. The wildtype zebra finch genome was found to have three intact genes in this cluster: CYP2J19A, CYP2J19B and CYP2J40. In yellowbeak, there are multiple mutations: loss of a complete CYP2J19 gene, a modified remaining CYP2J19 gene (CYP2J19yb), and a non-synonymous SNP in CYP2J40. In wildtype birds, CYP2J19 loci are expressed in keto-carotenoid-containing tissues: CYP2J19A only in retina and CYP2J19B in beak and tarsus and to a variable extent in the retina. In contrast, expression of CYP2J19 yb is barely detectable in the beak of yellowbeak birds. CYP2J40 has broad tissue expression and shows no differences between wildtype and yellowbeak. Our results indicate that CYP2J19 genes are strong candidates for the carotenoid ketolase, and imply that ketolation occurs in the integument in zebra finch. Since cytochrome P450 enzymes include key detoxification enzymes, our results raise the intriguing possibility that red coloration may be an honest signal of detoxification ability.
We thank the BBSRC (grant numbers BB/E017509/1 and BB/I02185X/1 to J. Sl., T. B, T. R. B), the EC Marie Curie International Outgoing Fellowship scheme (project 253300 to J. St.), the NERC Biomolecular Analysis Facility (NBAF961 to N.M., J. Sl.) and Murray Edwards College, Cambridge (N. M.) for funding. We thank Simon Griffith for wild zebra finch samples.
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External DOI: https://doi.org/10.1016/j.cub.2016.04.047
This record's URL: https://www.repository.cam.ac.uk/handle/1810/255812
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