The microarrays, with pieces of 40,000 lab rat genes, included 224 biotransformation or detoxification genes already identified in lab rats. Dearing decided to try lab rat microarrays on closely related packrats.
"We never have been able to survey this number of detoxification genes at once," Dearing says. "Prior to the advent of these microarrays, there haven't been techniques where we could look at detox genes comprehensively."
The microarray analysis shows which genes in the woodrats have been "expressed" or activated to produce enzymes that make toxins in creosote and juniper water soluble and thus easily excreted by the rodents.
The researchers collected eight packrats from each of two areas using live animal traps baited with peanut butter and oats. Mojave woodrats came from Lytle Ranch, a Nature Conservancy preserve in southwest Utah. Great Basin woodrats came from the White Rocks area of Tooele County, west of Salt Lake City.
Eight woodrats from each region were fed diets in which rabbit chow was treated either with creosote resin or with finely ground juniper leaves. Then the microarrays were used to determine which genes had been activated on each diet in each group of packrats.
-- "When both populations were fed juniper, we found fewer differences between the two populations in gene expression and also in their ability to eat juniper," Dearing says. "That says the Mojave woodrats haven't completely lost their ability to detoxify juniper yet." Both groups of packrats also lost weight, showing that they can only eat so much of even the more mildly toxic juniper, but must eat other available plants.
-- "Then we fed both groups creosote, and that allowed us to identify these 24
|Contact: Lee Siegel|
University of Utah