Researchers found a single gene is responsible for the evolution of multicellular organisms. The study is published in a recent issue of Nature Communications.
 
Researchers were looking for what caused single-celled organisms to evolve into multicellular organisms when they discovered the importance of a single gene, retinoblastoma, or RB. They found that RB, known for being defective in cancer patients, is a critical gene necessary for multicellular life. According to the author, previous theories indicated that multiple genes might be responsible for multicellularity.

"Not only did we find a critical gene for multicellularity, it turns out it turns out to be a tumor suppressor and it is much easier to evolve multicellularity than anticipated," author said.

They compared genomes of multicellular alga called Gonium pectorale and its single-celled alga relative, Chlamydomonas reinhardtii. The RB gene is in both algae but has small differences in structure and how it regulates cell cycles.

Expression of the Gonium retinoblastoma cell cycle regulator in unicellular Chlamydomonas causes it to become colonial. The presence of these changes in undifferentiated Gonium indicates extensive group-level adaptation during the initial step in the evolution of multicellularity.

"RB plays a fundamental role in cell multiplication by regulating cell cycles just before DNA replication starts," author said. "Cancer occurs when this gene is defective. In terms of cell cycle and cancer progression, think of RB like the brakes on your car. When the brakes are defective, there is no way to control how the vehicle stops."

Multicellularity has evolved dozens of times independently, according to the researchers.

http://www.k-state.edu/media/newsreleases/may16/multicellevolve5516.html