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Maize pest exploits plant defense compounds to protect itself

Typography

The western corn rootworm continues to be on the rise in Europe. Why attempts to biologically target this crop pest by applying entomopathogenic nematodes have failed, can now be explained by the amazing defense strategy of this insect. In their new study, scientists from the University of Bern, Switzerland, and the Max Planck Institute for Chemical Ecology in Jena, Germany, show that the rootworm larvae are able to sequester plant defense compounds from maize roots in a non-toxic form and can activate the toxins whenever they need them to protect themselves against their own enemies. (eLife, November 2017, DOI: 10.7554/eLife.29307.001)

The western corn rootworm continues to be on the rise in Europe. Why attempts to biologically target this crop pest by applying entomopathogenic nematodes have failed, can now be explained by the amazing defense strategy of this insect. In their new study, scientists from the University of Bern, Switzerland, and the Max Planck Institute for Chemical Ecology in Jena, Germany, show that the rootworm larvae are able to sequester plant defense compounds from maize roots in a non-toxic form and can activate the toxins whenever they need them to protect themselves against their own enemies. (eLife, November 2017, DOI: 10.7554/eLife.29307.001)

The western corn rootworm (Diabrotica virgifera virgifera) is a devastating pest of maize plants, which has spread throughout Europe. This year’s pest monitoring in Germany revealed that the number of beetles caught in traps has again multiplied in comparison to the previous year. The insect originates from Central America, from where it spread invasively throughout North America since the 1950s. Agricultural authorities in the US estimate that the western corn rootworm causes damage worth billions of dollars each year.

Plants deploy sophisticated defense strategies in order to fend off the many species of insects interested in feeding on their nutritious leaves or roots. Researchers from Bern and Jena have now investigated the case of a beetle larva, which exploits the plant’s defenses for its own use. Maize plants store defense compounds known as benzoxazinoids in their roots in a non-toxic form. If herbivores attack the plants, these molecules rapidly break down into compounds that are toxic for most insects. “We were able to show that the western corn rootworm stabilizes a toxic benzoxazinoid by adding a sugar molecule. This modified molecule is used directly to keep nematodes, used as a biological control, away. Moreover, rootworms can stabilize a second plant-derived benzoxazinoid, sequester its non-toxic form in their bodies, and activate it upon nematode attack”, explains first and lead author Christelle Robert, who initiated this project in Jena and continued it at the University of Bern. Hence, the rootworm once uses a double strategy to utilize plant defenses for its own protection.

Read more at Max Planck Institute for Chemical Ecology

Photo: The western corn rootworm (Diabrotica virgifera virgifera), orginally from Central America, is more and more frequently found in Europe. The increasing pest pressure is causing great concern among farmers.

Photo Credit: Nowlan Freese / Max Planck Institute for Chemical Ecology