In a paper published online in Nature Genetics June 11, evolutionary biologist Jianzhi (George) Zhang presents evidence for one such instance in a gene for an enzyme that helps leaf-eating monkeys digest their food.
"We know that parallel, or convergent, evolution is very common at the level of morphology---birds can fly, insects can fly, bats can fly, and they've all evolved this capability independently. But at the DNA and protein sequence level, it's very rare to find parallel evolution. This paper provides a real example," said Zhang, an associate professor of ecology and evolutionary biology.
The new work builds on previous research in which Zhang showed that the duplication of a gene encoding a pancreatic enzyme helped Asian colobine monkeys cope with an unusual diet.
"Colobines are different from other monkeys in that they primarily eat leaves rather than fruit or insects, and leaves are very difficult to digest," Zhang said. The monkeys manage with a digestive system similar to a cow's. Bacteria in the gut ferment the leaves and take up nutrients that are released in the process. The monkeys, in turn, digest the bacteria to recover the nutrients, such as protein and ribonucleic acid (RNA), a particularly important source of nitrogen in leaf eaters.
Zhang focused his attention on RNASE1, a pancreatic enzyme that breaks down bacterial RNA. Most primates have one gene encoding the enzyme, but he found that the douc langur, a colobine from Asia, has two---one encodes RNASE1, and its duplicate encodes a new enzyme, RNASE1B. The duplicate enzyme, it turns out, works better than the original in the acidic conditions of the colo
Source:University of Michigan