title: Herbivore-induced poplar cytochrome P450 enzymes of the CYP71 family convert aldoximes to nitriles which repel a generalist caterpillar.
abstract: Numerous plant species emit volatile nitriles upon herbivory, but the biosynthesis as well as the relevance of these nitrogenous compounds in plant-insect interactions remains unknown. Populus trichocarpa has been shown to produce a complex blend of nitrogenous volatiles, including aldoximes and nitriles, after herbivore attack. The aldoximes were previously reported to be derived from amino acids by the action of cytochrome P450 enzymes of the CYP79 family. Here we show that nitriles are derived from aldoximes by another type of P450 enzyme in P. trichocarpa. First, feeding of deuterium-labeled phenylacetaldoxime to poplar leaves resulted in incorporation of the label into benzyl cyanide, demonstrating that poplar volatile nitriles are derived from aldoximes. Then two P450 enzymes, CYP71B40v3 and CYP71B41v2, were characterized that produce aliphatic and aromatic nitriles from their respective aldoxime precursors. Both possess typical P450 sequence motifs but do not require added NADPH or cytochrome P450 reductase for catalysis. Since both enzymes are expressed after feeding by gypsy moth caterpillars, they are likely to be involved in herbivore-induced volatile nitrile emission in P. trichocarpa. Olfactometer experiments showed that these volatile nitriles have a strong repellent activity against gypsy moth caterpillars, suggesting they play a role in induced direct defense against poplar herbivores.
authors.affiliation: Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745, Jena, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Irmisch
authors.forename: Andrea
authors.initials: A
authors.lastname: Clavijo McCormick
authors.forename: Jan
authors.initials: J
authors.lastname: Günther
authors.forename: Axel
authors.initials: A
authors.lastname: Schmidt
authors.forename: Gerhard Andreas
authors.initials: GA
authors.lastname: Boeckler
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gershenzon
authors.forename: Sybille B
authors.initials: SB
authors.lastname: Unsicker
authors.forename: Tobias G
authors.initials: TG
authors.lastname: Köllner
mesh_terms: D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D060434:Herbivory; D007814:Larva; D009036:Moths / Q000187:drug effects* / Q000502:physiology; D009570:Nitriles / Q000378:metabolism*; D010091:Oximes / Q000737:chemistry / Q000378:metabolism*; D010802:Phylogeny; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000201:enzymology* / Q000235:genetics / Q000276:immunology; D017422:Sequence Analysis, DNA; D055549:Volatile Organic Compounds / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D009570:Nitriles; D010091:Oximes; D010940:Plant Proteins; D055549:Volatile Organic Compounds; C408881:phenylacetaldoxime; D003577:Cytochrome P-450 Enzyme System; C023728:acetaldehyde oxime
keywords: CYP71; Populus trichocarpa; cytochrome P450; direct defense; nitriles; volatiles