biology

Random Mutation May Have Started Multi-Celled Life

According to biochemists at the University of Oregon, it was just one mutation about 600 million years ago that may have kick started multicellular life on Earth. With that seemingly random event, a new protein function was formed that helped single-celled life transition into complex organisms.

The research helps to address several important questions scientists have about evolution, like how did life on Earth transition from single-celled to multi-celled?, and how do complex systems like those that allow cells to work together in an organized way, evolve the many different proteins they require? The findings were published in the open access journal eLife.

protein-mutation

The top image is a fluorescent micrograph of a dividing choanoflagellates, with its DNA in blue. The bottom is a colony of choanoflagellates. Image credit: Ken Prehoda

The team first studied choanoflagellates with the help of scientists from the University of California, Berkeley. Choanoflagellates are ocean dwelling, single celled organisms that are considered to be the closest living relative to animals. They then used gene sequences from more than 40 other organisms, and a technique known as ancestral protein reconstruction. This allowed scientists to work backwards through the evolutionary tree, see molecular changes, and infer how proteins formed in the past.

Results showed that the choanoflagellates tail plays a critical role in how they organize multicellular colonies – so much so that scientists think our single-celled ancestors may have had a similar one.

The team suggests the tails role became less important when a single mutation allowed one of the ancestral amoeba to arrange newly made cells. The protein that resulted from this mutation is found in all animals today and their simpler relatives, but absent in other life forms.

“This mutation is one small change that dramatically altered the protein’s function, allowing it to perform a completely different task,” said one of the authors Kenneth Prehoda. “You could say that animals really like these proteins because there are now over 70 of them inside of us,” he added.

Materials provided by the University of Oregon.

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