Induction of Glutathione S-Transferase in Helicoverpa zea Fed Cashew Flour

Helicoverpa zea and other insects have evolved strategies to counteract the plant protective proteins and defensive compounds they may encounter during feeding. We sought to take advantage of this phenomenon by identifying proteins up-regulated in H. zea in response to the inclusion of cashew nut flour in their diet. Tree nut and peanut seed storage proteins can act as defensive compounds protecting the tissue from insect damage by inhibiting digestion. When ingested by humans, these proteins can act as potent food allergens that may cause harmful physiological responses in food allergy affected individuals. Cashew allergens, such as the 2S albumin Ana o 3, have homology to protease or amylase inhibitors that inhibit digestion. Insects such as the corn earworm, H. zea, feed on various plant species that contain similar protease or amylase inhibitors and additional defensive compounds. Here, we compared the intestinal protein profile of H. zea fed on media containing pinto bean, cashew, or peanut. Through comparative feeding studies, mass-spectrometry, and glutathione binding assays we demonstrate that Glutathione S-transferases (GST) are specifically induced in the larvae of H. zea when cashew protein is included in their diet. We assessed the ability of purified H. zea GST proteins to break the disulfide bonds of cashew extract proteins and the purified Ana o 3 allergen. Continued research in this area could identify insect enzymes that may be useful in enzymatic processing steps to reduce or eliminate nut allergens and may have application in the food industry or health fields.