Study Explains How Corn Plants Fight Off Simultaneous Attacks

Corn plants face different herbivorous insects that chew on leaves, pierce and suck out sap or plant cell fluids, bore into stems, or consume the roots. Insects consume 6-19 percent of the world corn crop each year, while also spreading bacteria and viruses between plants. A recent study conducted by Professor Georg Jander's group at the Boyce Thompson Institute (BTI) found that corn plants make serious trade-offs as they defend themselves against multiple types of insects.

Corn plants have both physical and chemical defense mechanisms. To ward off aphids, the plants make callose, a carbohydrate that seals off the openings between cells and to stop aphids from sucking out the sap from tissues. Callose formation is triggered by a defensive compound called DIMBOA. In the event of a caterpillar attack, plants produce a compound called MBOA that deters their feeding. Both MBOA and DIMBOA are in the same metabolic pathway and come from a molecule called a benzoxazinoid.

As both defensive compounds come from the same parent molecule, the researchers thought that feeding by one group of insects might affect the plant's ability to fight off another group. To test this idea, the team grew seedlings of the common corn variety B73, and exposed some to caterpillars. They then seeded them with aphids, counting the number of offspring produced in pristine plants, compared to previously nibbled ones. The aphids consistently produced more offspring on corn that had been pre-chewed by caterpillars. The team bred B73 plants with the variety Ky21 to identify genes that play a role in such interaction and found that three genome regions, on chromosomes 1, 7 and 10, that appear to have a significant impact on a corn plant's aphid susceptibility.

For more details, read the news release at the BTI Press Room.