It’s Not Only the Gene That Counts, But How You Use It

Newswise — Scientists at the University of Idaho have discovered not only that different species sometimes use the same gene to produce the same adaptation, but also that how they use it can lead to different outcomes.

Erica Bree Rosenblum, assistant professor of biology, studied three species of lizards living in the White Sands region of New Mexico. Though the species are quite different from each other, they are similar in that they each evolved bleached backs in response to living in a white environment. She discovered that two of the three species used the same gene to change colors but through different mutations, and that the difference had important consequences for the lizards.

The findings were published last week in a paper titled, “Molecular and functional basis of phenotypic convergence in white lizards at White Sands,” in the Early Edition of the Proceedings of the National Academy of Science (PNAS) Online.

“It’s cool that really different species solve the same problem in a similar way,” said Rosenblum. “But what’s even cooler is that a very slight difference actually has a big effect on the lizards.”

The White Sands region consists of gypsum sand dunes covering a range of 275 square miles of desert. Though the formation of this white desert happened very recently – less than 7,000 years ago – many species have already adapted to the environment, making the region interesting to evolutionary biologists.

One adaptation involves changing colors from dark to light in order to become camouflaged from overhead predators. To find out if the same gene was used by different species to make this change, Rosenblum studied three species of lizards.

What she discovered is that two of the three species – the fence lizard and the whiptail lizard – did indeed use the same gene that controls the production of melanin; the same substance that controls the color of human hair. Other studies have shown mice and birds use this same gene to control color as well.

But Rosenblum took her research deeper. She discovered that the lizards use the gene in different ways, which affects whether a white back is a dominant or recessive trait, and thus the rate of adaptation.

“It shows a difference in the function of a single gene can actually matter,” she said.

The gene in question creates receptors that sit in the membranes of cells that make melanin and transmits a signal that controls melanin production. In fence lizards, the gene mutated so that the receptors no longer sit correctly into the membranes of the melanin cells. In whiptail lizards, the mutation affects how well the receptor transmitted the “on" and "off” signal to make melanin.

Of note, Rosenblum found the mutation causing the misfit receptors is a dominant trait while the mutation that messes up the signal transmission is recessive. This means fence lizards using the first mutation only need one copy of the mutated gene to be white, while whiptail lizards need two.

“What seems like a nitpicky technical detail about how the receptor is compromised actually affects the natural population of lizards,” said Rosenblum. “It changes how fast the white phenotypes spread in the population and whether migrants from one population moving to another can survive. It’s really fascinating.”

Read a summary of Rosenblum’s research by the New York Times at: http://www.nytimes.com/2010/01/05/science/05oblizard.html

For full text of Rosenblum’s research paper, visit PNAS online at: http://www.pnas.org/content/early/2009/12/15/0911042107.full.pdf+html.

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About the University of Idaho

Founded in 1889, the University of Idaho is the state’s flagship higher-education institution and its principal graduate education and research university, bringing insight and innovation to the state, the nation and the world. University researchers attract nearly $100 million in research grants and contracts each year; the University of Idaho is the only institution in the state to earn the prestigious Carnegie Foundation classification for high research activity. The university’s student population includes first-generation college students and ethnically diverse scholars. Offering more than 130 degree options in 10 colleges, the university combines the strengths of a large university with the intimacy of small learning communities. For information, visit www.uidaho.edu.