How emus and ostriches lost the ability to fly

Author: Tina Hesman Saey / Source: Science News

Evolutionary tweaks to DNA that bosses genes around may have grounded some birds.

New genetic analyses show that mutations in regulatory DNA caused ratite birds to lose the ability to fly up to five separate times over their evolution, researchers report in the April 5 Science. Ratites include emus, ostriches, kiwis, rheas, cassowaries, tinamous and extinct moa and elephant birds.

Only tinamous can fly.

Regulatory DNA gets its name because it’s involved in regulating when and where genes are turned on and off. It doesn’t contain instructions for making proteins. Researchers have long debated whether big evolutionary changes, such as gaining or losing a trait like flight, occur mostly because of mutations to protein-making genes tied to the trait, or result mainly from tweaks to the more mysterious regulatory DNA.

Revealing the importance of regulatory DNA in shaping evolution could shed light on how closely related species with the same genes, such as chimps and humans or moas and tinamous, can develop vastly different looks and abilities.

Scientists have tended to stress the importance of protein-coding changes affecting the evolution of various traits in many organisms. Examples are relatively easy to find. For instance, a previous study of flightless Galápagos cormorants suggested that mutations in a single gene shrank the birds’ wings (SN: 6/11/16, p. 11).

In general, mutations that alter proteins are likely to be more damaging than changes to regulatory DNA, and thus easier to spot, says Camille Berthelot, an evolutionary geneticist at the French national medical research institute INSERM in Paris. A protein may be involved in many biological processes throughout the body. “So everywhere this protein is [made], there’s going to be consequences,” she says.

By contrast, many pieces of DNA may be involved in regulating a gene’s activity, and each may work in only one or a few types of tissue. That reduces the damage that changing one regulatory segment might have, rendering those bits of DNA easy targets for evolution’s experiments. But, at the same time, it also makes it much harder to determine when regulatory DNA is actually involved in big evolutionary changes, says…

Click here to read more

The post How emus and ostriches lost the ability to fly appeared first on FeedBox.