Although it led to the evolution of multicellulared organisms that eventually became the complex humans that walk the Earth today, the cellular mechanism that began life 600 million years ago was very simple - in fact, researchers from the University of Oregon say it was just a single random mutation that led to the new protein function the helped the evolution of our single-celled ancestors. The research helps scientists better understand the process of evolution and also benefits those studying diseases such as cancer that result in damaged cells conflicting with other kinds of cells in our body and going back to a unicellular state.
"Proteins are the workhorses of our cells, performing a wide variety of tasks such as metabolism," Ken Prehoda, who headed the research, said in a press release. "But how does a protein that performs one task evolve to perform another? And how do complex systems like those that allow cells to work together in an organized way, evolve the many different proteins they require? Our work suggests that new protein functions can evolve with a very small number of mutations. In this case, only one was required."
Prehoda and his team examined choanoflagellates, which are a group of single-celled organisms that are believed to be the closest living relatives of animals. Although they can exist in a single-celled solitary form, these sponge-like, underwater organisms can also exist in multicellular colonies. Using ancestral protein reconstruction in combination with gene sequencing and computational methods, the team moved back in time through the evolutionary tree and were able to pinpoint molecular changes and examine protein roles years ago.
The team discovered a single mutation that was responsible for opening the door for the evolution of multicellular animals and also found that the choanoflagellate flagellum is crucial for the organization of its multicellular colonies, suggesting that this could have been the case for our ancient single-celled ancestor. However, as time went on, this tail became less and less important.
"This mutation is one small change that dramatically altered the protein's function, allowing it to perform a completely different task," Prehoda said. "You could say that animals really like these proteins because there are now over 70 of them inside of us."
The findings were published in the Jan. 7 issue of eLife.
