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Plant Physiology Preview Published on January 11, 2008; 10.1104/pp.107.112185
OPEN ACCESS ARTICLE
Received October 31, 2007 Indole-3-acetonitrile production from indole glucosinolates deters oviposition by Pieris rapae (white cabbage butterfly)
The Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853, USA * Corresponding author; email: gj32{at}cornell.edu.
Like many crucifer-specialist herbivores, Pieris rapae (white cabbage butterfly) uses the presence of glucosinolates as a signal for oviposition and larval feeding. Arabidopsis thaliana glucosinolate-related mutants provide a unique resource for studying the in vivo role of these compounds in affecting P. rapae oviposition. Low indole glucosinolate cyp79B2 cyp79B3 mutants received fewer eggs than wild-type, confirming prior research showing that indole glucosinolates are an important oviposition cue. Transgenic plants overexpressing epithiospecifier protein (ESP), which shifts glucosinolate breakdown towards nitrile formation, are less attractive to ovipositing P. rapae females. Exogenous application of indol-3-ylmethylglucosinolate breakdown products to cyp79B2 cyp79B3 mutants showed that oviposition was increased by indole-3-carbinol and decreased by indole-3-acetonitrile. P. rapae larvae tolerate a cruciferous diet by using a gut enzyme to redirect glucosinolate breakdown toward less toxic nitriles, including indole-3-acetonitrile, rather than isothiocyanates. The presence of indole-3-acetonitrile in larval regurgitant contributes to reduced oviposition by adult females on larvae-infested plants. Therefore, production of nitriles via ESP in cruciferous plants, which makes the plants more sensitive to generalist herbivores, may be a counter-adaptive mechanism for reducing oviposition by P. rapae and perhaps other crucifer-specialist insects.
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