A new study published in Nature is elucidating the role that prions may play in the evolution of yeast, reports New Scientist's Andy Coghlan. Researchers at the Whitehead Institute for Biomedical Research show that yeast undergoes a kind of "combinatorial evolution" where it is able to transform a protein called Sup35 into a prion in times of stress, which then leads to the production of new proteins that were previously not needed, some of which may be helpful to the yeast's survival — all without any changes to the yeast's DNA. "[Whitehead researcher Susan] Lindquist grew the yeast in a hostile environment — either oxygen-depleted or abnormally acidic, for example — and then exposed the survivors to a chemical that destroys prions," Coghlan says. "Many colonies withered, showing that the prions were responsible for their competitive edge. What's more, the prions are passed down in mating, so daughter cells will also make the same suite of survivor proteins."
Although it's currently unclear whether this prion method of evolution applies to species other than yeast, the implication, the researchers say, is that not all evolution is driven through changes to DNA.