For pea aphids, the ability to go forth and multiply can depend on a single gene, according to new research.
An overheated aphid with a mutation in that gene can't reproduce.
The gene isn't even in the insect -- it's in tiny symbiotic bacteria housed inside special cells inside the aphid.
"It's the first time a mutation in a symbiont has been shown to have a huge impact on host ecology," said Nancy A. Moran, Regents' Professor of ecology and evolutionary biology at The University of Arizona in Tucson. "One version of the gene is good if the aphids experience heat, and the other version is good if they are in cool conditions."
Neither organism can survive on its own. The Buchnera aphidicola bacteria, which cannot live on their own, supply the aphids, Acyrthosiphon pisum, with essential nutrients.
UA researchers Helen E. Dunbar, a senior research specialist, Alex C. C. Wilson, now at the University of Miami in Coral Gables, Fla., Nicole R. Ferguson, a member of UA's Undergraduate Biology Research Program, and Moran are publishing their findings in the May 2007 issue of PLoS Biology.
Their research paper is titled "Aphid Thermal Tolerance is Governed by a Point Mutation in Bacterial Symbionts." The research was funded by the National Science Foundation and the National Institutes of Health. Howard Hughes Medical Institute provides funding for the UA's Undergraduate Biology Research Program.
Aphids reproduce asexually, so juveniles are clones of their mothers. The symbiotic bacteria are passed on from mother to child. Moran's lab maintains colonies of aphids, each descended from a single ancestral aphid mother.
The scientists found the heat-intolerant gene by accident.
Wilson, then a UA postdoctoral fellow in Moran's lab, was testing the response of some aphid and bacterial genes from one aphid colony. The bacteria's ibpA gene codes for a protein, called a heat-shock protei
Contact: Mari N. Jensen
University of Arizona