Submitted to: Nature
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2002
Publication Date: 10/1/2002
Citation: PECHAN, T., COHEN, A.C., WILLIAMS, W.P., LUTHE, D.S. INSECT FEEDING MOBILIZES A UNIQUE PLANT DEFENSE PROTEASE THAT DISRUPTS THE PERITROPHIC MATRIX OF CATERPILLARS. NATURE. 2002. v.99. p. 13319-13323. Interpretive Summary: Corn with resistance to feeding by fall armyworm and southwestern corn borer was developed by USDA-ARS scientists at Mississippi State University. Within one hour after larvae begin feeding, a unique protein starts accumulating in the corn leaf at the larval feeding site. The gene that encodes this protein was transferred using genetic engineering techniques to undifferentiated corn callus tissue. When the callus was fed to fall armyworm larvae, growth of the larvae was reduced 20 to 40%. The membrane lining of the larval midgut was damaged when larvae were fed plant tissue containing this tissue. Transfer of the gene encoding this protein into other crop plants may increase their resistance to insect damage.
Technical Abstract: Plants attacked by herbivorous insects frequently respond by synthesizing defensive proteins that directly protect the plant from the insect. We have demonstrated that a unique 33-kD cysteine proteinase accumulated in response to caterpillar feeding in lepidoptera-resistant maize (Zea mays L.) genotypes. The proteinase accumulates in the mid-whorl within one hour rof fall armyworm (Spodoptera frugiperda) feeding. Decreased nutrient utilization by larvae reared on the mid-whorl results in growth reduction of approximately 50%. The proteinase is unique because sequence analysis of its gene, mir1, shows that the 25 carboxyl-terminal amino acids have no match in available databases. Black Mexican Sweet (BMS) callus transformed with mir1 reduced larval growth 60 to 80%. In this study, we show that the larval peritrophic matrix, which protects the midgut of most insects, is severely damaged when larvae are reared on resistant plants or transgenic BMS. This is the first report showing that a plant proteinase damages the insect peritrophic matrix structure. It represents an unusual and novel host plant resistance mechanism. Transfer of mir1 to other plant species may enhance their resistance to herbivorous insects.