Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/1997
Publication Date: N/A
Interpretive Summary: Insects continue to cause devastating crop losses. The use of genetic engineering allows for the introduction of novel, protein-based resistance that may be difficult or impossible to introduce by conventional breeding. However, the number of useful proteins that have been identified is limited at present. A protein derived from a fungus was tested against beetles and dcaterpillars, and either killed or repelled several different ones. The protein is active enough at the concentrations tested to have significant potential for enhancing insect control through genetic engineering of plant or insect pathogens.
Technical Abstract: The fungus feeding beetle, Carpophilus freemani, consumed equal quantities of young mycelia, less phialides bearing mature spores and much fewer phialides bearing developing spores of Aspergillus restrictus compared to those of Aspergillus nidulans in choice tests. The degree to which the fungal structures tested were consumed is inversely related to the localization of high levels of restrictocin, a ribosome inactivating protein, to those structures. Pure restrictocin added to the insect diet at 1000 ppm killed 38.5% of C. freemani larvae and 62.5% of Spodoptera frugiperda larvae in 48 hrs, but did not affect C. freemani adults or Helicoverpa zea larvae over the same interval. In choice assays, 1000 ppm of restrictocin deterred feeding by adult C. freemani and Sitophilus zeamais compared to control diets. Thus, restrictocin production and localization may have a natural defensive role against insect feeding at times critical to spore formation by A. restrictus, and may have potential as an insect control agent when genetically engineered into appropriate plants.