Sucrose Utilization in Budding Yeast as a Model for the Origin of Undifferentiated Multicellularity

FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts, United States of America.
PLoS Biology (Impact Factor: 11.77). 08/2011; 9(8):e1001122. DOI: 10.1371/journal.pbio.1001122
Source: PubMed

ABSTRACT Author Summary
The evolution of multicellularity is one of the major steps in the history of life and has occurred many times independently. Despite this, we do not understand how and why single-celled organisms first joined together to form multicellular clumps of cells. Here, we show that clumps of cells can cooperate, using secreted enzymes, to collect food from the environment. In nature, the budding yeast Saccharomyces cerevisiae grows as multicellular clumps and secretes invertase, an enzyme that breaks down sucrose into smaller sugars (glucose and fructose) that cells can import. We genetically manipulate both clumping and secretion to show that multicellular clumps of cells can grow when sucrose is scarce, whereas single cells cannot. In addition, we find that clumps of cells have an advantage when competing against “cheating” cells that import sugars but do not make invertase. Since the evolution of secreted enzymes predates the origin of multicellularity, we argue that the social benefits conferred by secreted enzymes were the driving force for the evolution of cell clumps that were the first, primitive form of multicellular life.

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