In order for multicellular organisms to form, most cells need to sacrifice their ability to reproduce, an altruistic action that favors the whole but not the individual, Ratcliff said. For example, all cells in the human body are essentially a support system that allows sperm and eggs to pass DNA along to the next generation. Thus, multicellularity is by its nature extremely cooperative. "Some of the best competitors in nature are those that engage in cooperation, and our experiment bears that out," said Travisano.
Evolutionary biologists have estimated that multicellularity evolved independently in about 25 groups. Travisano and Ratcliff wonder why it didn't evolve more often in nature, since it's not that difficult to recreate it in a lab. Considering that trillions of one-celled organisms lived on the Earth for millions of years, it seems as if it should have, Ratcliff said.
Maybe that's a question they will answer in the future, using the fossil record for thousands of generations of their multicellular clusters, which is stored in a freezer in Travisano's lab. Since the frozen samples contain multiple lines that independently became multicellular, they can compare them to learn if similar or different mechanisms and genes were responsible in each case, Travisano said.
The research duo's next steps will be to look at the role of multicellularity in cancer, aging and other critical areas of biology.
"Our multicellular yeast are a valuable resource for investigating a wide variety of medically and biologically important topics," Travisano said. "Cancer was recently described as a fossil from the origin of multicellularity, which can be directly investigated with the yeast system. Similarly the origins of aging, development, and the
|Contact: Jeff Falk|
University of Minnesota