|Tumlinson Iii, James|
Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2000
Publication Date: 12/19/2000
Citation: Frey, M., Stettner, C., Pare, P.W., Schmelz, E.A., Tumlinson Iii, J.H., Gierl, A. 2000. An herbivore elicitor activates the gene for indole emission in maize. Proceedings of the National Academy of Sciences. 97(26):14801-14806. Interpretive Summary: When the leaves of corn seedlings are damaged by feeding beet armyworm caterpillars they emit an odor, comprised of a blend of volatile chemicals, that attracts natural enemies of the caterpillars. In a collaborative effort, Scientists at the Technical University of Munich, and the Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL, have discovered a new enzyme that catalyzes the formation of indole, one of the constituents of the odor blend. Furthermore, the gene for this enzyme is selectively activated by a compound in the spit of the caterpillars, but not by mechanical wounding or trea ent with buffer. Plants that are not wounded do not release these odors. These results indicate that specific genes for enzymes that regulate biosynthesis of plant volatiles are activated by components of the caterpillar spit. Thus, it may be possible to develop plants in which these genes are enhanced and thus, plants attacked by insect pests would produce larger amounts of the odors that attract natural enemies of their attackers. This will lead to development of more effective biological control of insect pests of agricultural crops with native natural enemies.
Technical Abstract: Maize and a variety of other plant species release volatile compounds in response to herbivore attack that serve as chemical cues to signal natural enemies of the feeding herbivore. N-(17- hydroxylinolenoyl)-L-glutamine is an elicitor component that has been isolated and chemically characterized from the reguritant of the herbivore pest beet armyworm. This fatty acid derivative, referred to as volicitin, triggers the synthesis and release of volatile components, including terpenoids and indole in corn. Here we report on a new enzyme, indole-3-glycerol phosphate lyase (IGL) that catalyses the formation of free indole and is selectively activated by volicitin. IGL's enzymatic properties are similar to BX1 the maize enzyme that serves as the entry point to the secondary defense metabolites DIBOA and DIMBOA. Gene sequence analysis indicates that Igl and Bx1 are evolutionary related to the tryptophan synthase alpha subunit.