The gene makes an enzyme that lets the birds convert yellow pigments, which they eat, into red ones, which are deposited in their feathers or beaks. Two separate teams made the discovery, by examining the DNA of birds which either gained or lost their redness. One focussed on a finch which sometimes loses its red beak; the other on a type of canary bred to be entirely red. Both studies are published in the journal Current Biology. "Birds cannot synthesise these red pigments endogenously. They have to obtain them from their diet," Dr Miguel Carneiro from the Universidade do Porto, Portugal, told.
"It was known for a long time that an enzymatic conversion is needed to produce the red pigments. So many groups of geneticists and physiologists, for many decades, have tried to identify the enzyme that does this conversion." Dr Carneiro and his colleagues began their search with the "red factor" canary - a popular pet that originated in the 1920s, when bird fanciers crossed common, yellow canaries with the vibrant South American red siskin.
"By a number of crosses, throughout many generations, they fixed the ability to convert yellow pigments into red pigments, in some breeds of canary.
"What we did… is try to look at sections of the genome in red factor breeds that actually belong to the red siskin - and that's how we got to the gene. Some people consider it to be the first genetically engineered species," Dr Carneiro said."We were studying a loss-of-function mutation, going from red to yellow, whereas they were studying a gain-of-function mutation: canaries aren't normally red, and they'd gained a mutation from another species," he told.
"In science… to demonstrate that a gene, a protein, whatever it is, is involved in something, you want to show that it is both necessary - it's required for that thing to happen - and also that it's sufficient, which means that it, on its own, can do the job. "Here, we've shown that the gene is necessary, and they've shown that it's sufficient."
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