Wheat Chemicals Starve Insect Pests



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15 January 2007 - Insects can starve to death in the middle of a wheat field, according to new research published in the journal Molecular Plant Pathology. Researchers at the US Department of Agriculture and Purdue University believe that the protein in the wheat plant attacks the stomach lining of Hessian fly larvae, giving the plant a level of resistance to the agricultural pest.

"Usually we expect the plant to fortify its cell walls or make poisons to use against insects and pathogens," said researcher Christie Williams. In this case, however, the protein HFR-3, one of a class of proteins called lectins, interacts with chitin, a carbohydrate that lines the larvae’s guts. This interaction damages the stomach lining in such a way that the insects can’t absorb nutrients from their food, starving them even though they’re eating.

While some fly larvae can remove HFR-3 from their bodies and survive, other larvae are inevitably susceptible. However, scientists believe that resistant wheat plants produce multiple lectins, increasing their chances of eliminating as many larvae as possible. In addition to the interaction, the proteins taste bad to the insects and are mildly toxic.

The characterization of this process is an important step in understanding the complex molecular interactions between wheat and Hessian flies. The fly larvae are particularly harmful to crops because their feeding cause plant cells in the areas to develop abnormally and produce more of the nutrients the flies prefer.

In return, resistant plants respond to fly larvae feeding by boosting their lectin production by as much as 3,000 times. However, lectin increases only occur in the areas the plant cells attack, making this a relatively energy-efficient response, especially compared with the costs to the plant of thickened cell walls or general toxins.

"Figuring out some of the ways that a plant is able to respond to insects with resistance will be useful in crop breeding programs," Williams explained. Researchers are continuing to investigate the timing of these genetic interactions between the two organisms in hopes of finding a way to alter wheat genes that the flies normally manipulate so that the plants produce substances poisonous to the larvae rather than the flies’ intended nutrients.

Emma Wear