Insects take a bigger bite out of plants in a higher CO2 world

The team turned its attention to the hormonal signaling pathways of the plants, focusing on a key defensive chemical the plants produced to ward off an insect attack. When insects eat their leaves, soybeans and other plants produce a hormone, jasmonic acid, that starts a chain of chemical reactions in the leaves that boost their defenses. Normally this cascade leads to the production of high levels of a compound called a protease inhibitor. When the insects ingest this enzyme, it inhibits their ability to digest the leaves.

“What we discovered is that leaves grown under high CO2 lose their ability to produce jasmonic acid, and that whole defense pathway is shut down,” Delucia said. “The leaves are no longer adequately defended.”

The higher carbohydrate content of the leaves and the lack of chemical defenses allowed the adult insects to feast and live longer and produce more offspring.

“This study demonstrates that global environmental change is multifaceted,” Berenbaum said. “The impact of elevated carbon dioxide on crippling the capacity of the plant to respond to insect damage is exacerbated by the presence of invasive insect pests in soybean fields. The Japanese beetle, as the name suggests, is a relatively recent arrival in Illinois soybean fields. It is causing considerable damage now but this study suggests that its ability to inflict damage will only increase over time.”

The researchers, both of whom also are affiliated with the university’s Institute for Genomic Biology, will now seek to determine whether the same process occurs in other plants.

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Editor’s note: To reach Evan DeLucia, call 217-333-6177; e-mail: .

To reach May Berenbaum, call 217-333-7784; e-mail: .