We would all like to believe that there is a kind of karma in life that guarantees those who cheat eventually pay for their bad behavior, if not immediately, then somewhere down the line. But a study of a new gene in the amoeba Dictyostelium discoideum suggests that, at least for amoebae, it is possible to cheat and get away with it.
The experimental work was conducted by then graduate student Lorenzo Santorelli as part of a collaboration between evolutionary biologists David C. Queller and Joan E. Strassmann of Rice University and Gadi Shaulsky and Adam Kuspa of Baylor College of Medicine. Santorelli has since moved to Oxford University and his advisors to Washington University in St. Louis, where Queller is the Spencer T. Olin Professor of Biology and Strassmann is a professor of biology, both in Arts & Sciences.
The cheat in question is putting more than your clone's fair share of cells into a communal spore body, so that your genome dominates the next generation of amoebae. The idea has always been that cheating clones pay a price in the form of reduced evolutionary fitness in some other chapter of their lives.
In work described in the Jan. 9 issue of BMC Evolutionary Biology, the scientists tested the fitness of a knockout mutant (an amoeba with one disabled gene) called CheaterB. When mixed with equal parts of a wild-type clone, the cheater clone contributed almost 60 percent of the cells in the spore body, 10 percent more than its fair share.
The scientists ran CheaterB cells through exhaustive tests of their ability to grow, develop, form spores and germinate. CheaterB did just as well in these tests as its ancestor wild strain. Under laboratory conditions, at any rate, CheaterB didn't seem to be paying a fitness cost for cheating.
The study raises important questions about the tension between cooperation and cheating. Why would breaking something that is presumably functional (by knocking out
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Washington University in St. Louis