| Abstract Detail
Plant-Pest Interactions Gonzales-Vigil, Eliana [1], Chen, Hui [2], Howe, Gregg [3]. Shotgun proteomic analysis of insect feces: A novel approach to identify hyperstable plant defense proteins that impair insect digestive physiology. Plant defense against insect herbivores is mediated in part by enzymes that exert toxic or antinutritional effects in the insect gut. Little is known about the evolutionary origins of these enzymes, their distribution in the plant kingdom, or the mechanisms by which they act in the protease-rich environment of the animal digestive tract. To test the hypothesis that midgut-active plant proteins are inherently stable in the insect digestive tract, we used LC-MS/MS to identify proteins that accumulate in feces (frass) of specialist (Manduca sexta) and generalist (Trichoplusia ni) insect herbivores reared on tomato (Solanum lycopersicum). Among the tomato proteins identified were several jasmonate-inducible proteins that have a known or proposed role in anti-insect defense. Subtilisin-like proteases and other pathogenesis-related proteins, as well as proteins of unknown function, were also catalogued. One of the most abundant proteins excreted in M. sexta and T. ni frass was a jasmonate-inducible isoform (TD2) of threonine deaminase. Ingestion of tomato foliage by lepidopteran larvae triggered proteolytic removal of TD2’s C-terminal regulatory domain, resulting in an enzyme that degrades threonine without being inhibited through feedback by isoleucine. This proteolytically processed form of TD2 exhibited biochemical properties that are consistent with a post-ingestive role in defense. Molecular analyses provided evidence that TD2 evolved from a “housekeeping” TD isozyme (TD1) that functions in the biosynthesis of isoleucine in planta. We conclude that proteomic analysis of frass from insect herbivores provides a robust experimental approach to identify novel proteins that serve important roles in plant defense against biotic stress. This research was supported by grants from the USDA/NRI and DOE.
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1 - Michigan State University, DOE-Plant Research Laboratory, 122 Plant Biology, East Lansing, MI, 48824, USA
2 - Michigan State University, DOE-Plant Research Laboratory
3 - Michigan State University, DOE-Plant Research Laboratory, Department of Biochemistry and Molecular Biology
Keywords:
threonine deaminase
plant-insect interaction
jasmonic acid
proteomics
tomato.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P14001
Abstract ID:161 |
