|Tumlinson Iii, James|
Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2003
Publication Date: 6/10/2003
Citation: LAIT, C.G., ALBORN, H.T., TEAL, P.E., TUMLINSON III, J.H. RAPID BIOSYNTHESIS OF N-LINOLENOYL-L-GLUTAMINE, AN ELICITOR OF PLANT VOLATILES, BY MEMBRANE ASSOICATED ENZYME(S) IN MANDUCA SEXTA. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES. 100(12):7027-7032. 2003. Interpretive Summary: Tobacco hornworm (THW) regurgitant contains compounds, called elicitors, that are made by coupling different amino acids and fatty acids. During herbivory, these elicitors come in contact with damaged leaves and trigger plants to emit volatile chemicals that attract the natural enemies of foraging caterpillars. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA-ARS, Gainesville, Florida have been studying how elicitors are made by the tobacco hornworm. They discovered that N-linolenoyl-L-glutamine, an elicitor found in many species of caterpillars, is made by enzymes found in cellular membranes from several THW tissues. The scientists demonstrated that the elicitor could be synthesized rapidly in the laboratory by simply combining partially purified enzyme from salivary gland or gut tissues, linolenic acid, and glutamine. Results of this research demonstrate for the first time that elicitors found in caterpillar regurgitant are made by enzymes located in caterpillar tissues and not by gut bacteria.
Technical Abstract: In response to elicitors found in the oral secretions of caterpillars, plants produce and release volatile chemicals that attract predators and parasitoids of the caterpillar while it feeds. The most prevalent elicitors are fatty acid amides consisting of 18-carbon polyunsaturated fatty acids coupled with L-glutamine. We demonstrate rapid CoA- and ATP-independent in vitro biosynthesis of the fatty acid amide elicitor, N-linolenoyl-L-glutamine, by microsomal fractions of several alimentary tissues in Manduca sexta. N-linolenoyl-L-glutamine is a structural analog of several other elicitors including volicitin, the first fatty acid amide elicitor identified in caterpillars. The enzyme(s) that catalyzed biosynthesis of N-linolenoyl-L-glutamine was localized within the integral membrane protein fraction extracted from microsomes by Triton X-114 detergent phase partitioning and had maximum activity at alkaline pH. We found no evidence suggesting microbial or tissue-independent biosynthesis of N-linolenoyl-L-glutamine in M. sexta. The in vitro biosynthesis of N-linolenoyl-L-glutamine by membrane associated enzyme(s) in M. sexta represents the first direct evidence of fatty acid amide synthesis by caterpillar tissues.