A novel genetic study has revealed why chickens have yellow legs, demonstrating that though Charles Darwin was right about many things, his view on the origins of the chicken was not entirely correct. The study, published February 29 in the open-access journal PLoS Genetics, reveals the genetic basis for the appearance of yellow skin in billions of chickens raised worldwide.
Yellow-skinned chickens have a different version of a gene than their white-skinned cousins. Darwin believed that all chickens came from a wild species known as the red junglefowl. When the researchers looked for the yellow-skin gene in the red junglefowl, they only found the genetic variant that codes for white skin. More surprisingly, when they finally did find the yellow-skin version of the gene, it was present in a completely different wild species: the grey junglefowl.
Greger Larson, a Research Fellow at Uppsala University and at Durham University, UK said: “Darwin recognized the importance of studying domestic animals as a model of evolution and this insight has proved enormously influential. The ironic thing is that he believed that dogs were hybrids of several wild ancestors but that chickens only had one, and he was wrong on both counts.”
Yellow coloring comes from pigments found in feed called carotenoids. The gene in question codes for an enzyme that degrades carotenoids into a colorless form. White-skinned chickens express this enzyme in skin. In contrast, yellow–skinned chickens do not express the enzyme in skin, allowing the carotenoids to accumulate and produce yellow coloring. Interestingly, the gene functions normally in other tissues and yellow-skinned chickens have no general defect in carotenoid metabolism.
“This is a beautiful demonstration of how important regulatory mutations are for evolutionary changes” said Leif Andersson, leader of the research team. “What we are interested in knowing now is why yellow skin in chickens is so ubiquitous. It could have been that yellow skin was perceived to be a marker of health or size or egg production, or it could just be that yellow skin was fun to look at. We’re really not sure. Furthermore, the gene we have identified may be important for carotenoid-based pigmentation in other species like the pink color of the flamingo; the yellow legs of many birds of prey including eagles, falcons and hawks; the pink muscles of salmon, and even skin color in humans.”
This project was funded by the European Molecular Biology Organization, the Swedish Foundation for Strategic Research, and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning and the Swedish Research Council.
PLEASE ADD THIS LINK TO THE PUBLISHED ARTICLE IN ONLINE VERSIONS OF YOUR REPORT: http://www.plosgenetics.org/doi/pgen.1000010
CITATION: Eriksson J, Larson G, Gunnarsson U, Bed’hom B, Tixier-Boichard M, et al. (2008) Identification of the Yellow Skin Gene Reveals a Hybrid Origin of the Domestic Chicken. PLoS Genet 4(2): e1000010. doi:10.1371/journal.pgen.1000010
RELATED IMAGE FOR PRESS USE: http://www.plos.org/press/plge-04-02-29-andersson.jpg
This press release refers to an upcoming article in PLoS Genetics. The release is provided by the article authors and/or their institutions. Any opinions expressed in this release or article are the personal views of the journal staff and/or article contributors, and do not necessarily represent the views or policies of PLoS. PLoS expressly disclaims any and all warranties and liability in connection with the information found in the releases and articles and your use of such information.
About PLoS Genetics
PLoS Genetics (http://www.plosgenetics.org) reflects the full breadth and interdisciplinary nature of genetics and genomics research by publishing outstanding original contributions in all areas of biology. All works published in PLoS Genetics are open access. Everything is immediately and freely available online throughout the world subject only to the condition that the original authorship and source are properly attributed. Copyright is retained by the authors. The Public Library of Science uses the Creative Commons Attribution License.
About the Public Library of Science
The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource. For more information, visit http://www.plos.org.
AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.