But what, precisely, conducts this nuclear traffic?
The flow, Roper and his colleagues discovered, is "propelled by pressure gradients across the colony in a complicated, mutely-directional network." By demonstrating how a variety of different pressures throughout the colony determine the speed and direction of flow, Roper illustrates how the apparently random network of tubes is actually exquisitely engineered to optimally mix the nuclei.
"To understand whether this mixing is engineered into the fungus, we need to figure out mathematically what the alternatives are," said Roper, who received an Alfred P. Sloan Foundation Research Fellowship last year.
To that end, the researchers studied the geometry of the network and then compared it to alternative, mathematically generated networks to see whether the fungus' natural network was optimal for mixing the genetically different nuclei. They found that it was.
To confirm their finding, they muted a gene in the fungus cell, changing the network. They found that in the genetically altered network, the nuclei tended to segregate out that is, nuclei that were the same genetically tended to group together rather than mix.
"The flow helps the fungus tolerate being genetically diverse within itself," Roper said. "That is not something any other class of organism does. There are millions of species of fungi, and many of them have this internal genetic diversity. In a person, we have a word for genetic diversity: cancer. But the fungus doesn't mind; it helps the fungus."
The benefits of being multicellular
Roper's goal is to apply mathematics to make new discoveries about how cells solve physical challenges. Those challenges and the solutions organisms have found for them have left deep imprints on how life has e
|Contact: Stuart Wolpert|
University of California - Los Angeles