Crop Protection Initiative takes new direction

Gustavo MacIntosh, assistant professor in the Department of Biochemistry, Biophysics and Molecular Biology, is studying soybean plant responses to aphid infestation.
Gustavo MacIntosh, assistant professor in the Department of Biochemistry, Biophysics and Molecular Biology, is studying soybean plant responses to aphid infestation.

This year Iowa suffered extensive outbreaks of soybean aphids, Aphis glycines. Millions of acres of farmland were sprayed to control the pest, because if left untreated, aphids can reduce soybean yields by up to 40 percent.

Originating from Asia, these aphids first appeared in the Midwest in 2000, and every few years since, troublesome outbreaks have occurred.

To develop new tools for managing soybeans aphids, the Plant Sciences Institute has launched a new project in the Crop Protection Research Initiative. Funding from the institute and the Iowa Soybean Association is making it possible to attack the problem from two different angles.

Gustavo MacIntosh, assistant professor in the Department of Biochemistry, Biophysics and Molecular Biology, will use microarrays—gene chips containing copies of soybean genes -to compare the gene expression patters of resistant and susceptible aphid infested soybean plants.

“This will give us a very good idea of the signaling and metabolic networks that function in this response,” said MacIntosh.

Additionally, MacIntosh's lab will study the differences in chemical makeup of resistant and susceptible soybean plant cells. This “metabolomic” information will be meshed with the gene expression date to glean a full view of the plant's defense mechanisms.

“With microarray analyses we know the players, but we don't know the game,” said MacIntosh. “With metabolomics we know the game—we know exactly what is changing in the plant at the level of metabolites and what has an effect on the aphids.”

MacIntosh's preliminary research suggests that soybean plants respond differently to predation from aphids as opposed to other insects and that stress plays an important role in modulating these responses.

It is the hope that MacIntosh's research will help breeders or genetic engineers to develop more resistant soybean plants.

Allen Miller, director of CPRES and professor in the Departments of Plant Pathology and Biochemistry, Biophysics and Molecular Biology, is working with Bryony Bonning, CPRES affiliate and professor in the Department of Entomology, to develop the equivalent of a Bt toxin for aphids. They are attempting to coax viruses from a variety of aphid species to control soybean aphids.

Miller and Bonning are also developing a virus-based tool called virus inducted gene silencing (VIGS) to characterize aphid gene expression. Using a virus to introduce an aphid gene of interest, the host will see it as an “alien gene” and destroy that gene and its own in the process.

“We can use VIGS to knock out genes in aphids of interest and see how that affects their ability to infect plants,” said Miller.

Additionally, Bonning's lab is sampling aphids across Iowa in search of new soybean aphid viruses. The high soybean aphid populations in 2007 should favor the presences of viruses.

“The Crop Protection Research Initiative fills an important niche between basic and applied research, but it's on crops specific to Iowa, an interesting combination,” said Miller.