| Abstract Detail
Plant-Pest Interactions Schmelz, Eric A. [1], LeClere, Sherry [2], Carroll, Mark J. [2], Alborn, H [2], Teal, P [2]. Cowpea (Vigna unguiculata) Chloroplastic ATP Synthase is the Source of Multiple Plant Defense Elicitors During Insect Herbivory. In cowpea (Vigna unguiculata), fall armyworm (Spodoptera frugiperda) herbivory and oral secretions (OS) elicit phytohormone production and volatile emissions due to inceptin [Vu-In; +ICDINGVCVDA-], a peptide derived from chloroplastic ATP synthase &[gamma]-subunit (cATPC) proteins. Induced plant volatiles can function as attractants for predators and parasitoids, the natural enemies of insect pests. During herbivory, we hypothesized that insect gut proteolysis should result in a mixture of inceptin-related peptides. In this study, we identified three additional cATPC fragments, namely Vu-GE+In [+GEICDINGVCVDA-], Vu-E+In [+EICDINGVCVDA-], and Vu-In-A [+ICDINGVCVD-]. Leaf bioassays for induced-ethylene (E) production demonstrated similar EC50 values of 68, 45, and 87 fmol leaf-1 for Vu-In, Vu-E+In, and Vu-GE+In, respectively; however, Vu-In-A proved inactive. Shortly following ingestion of recombinant proteins harboring cATPC sequences, larval OS revealed similar concentrations of the three elicitors with 80% of the potential inceptin-related peptides recovered. Rapidly shifting peptide ratios over time were consistent with continued proteolysis and the preferential stability of inceptin. Likewise, larvae ingesting host plants with inceptin precursors containing an internal trypsin cleavage site rapidly lost OS-based elicitor activity. OS containing inceptin elicited a rapid and sequential induction of defense-related phytohormones (JA), E, and salicylic acid (SA) at 30, 120, 240 min, respectively and also the volatile (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT). Similar to established peptide signals such as systemin and flg22, amino acid substitutions of Vu-In demonstrated an essential role for aspartic acid residues and an unaltered C-terminus. In selected legumes, insect gut proteolysis following herbivory generates inappropriate fragments of an essential plant metabolic enzyme enabling non-self recognition.
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1 - USDA-ARS CMAVE, Chemistry, 1600 SW 23rd Drive, Gainesville, FL, 32608, USA
2 - USDA-ARS CMAVE, Chemistry
Keywords:
insect herbivory
peptide elicitor
ethylene
jasmonic acid
salicylic acid
plant-insect interaction
volatiles.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P14004
Abstract ID:250 |
