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Herbivore‐induced poplar cytochrome P450 enzymes of the CYP 71 family convert aldoximes to nitriles which repel a generalist caterpillar
Author(s) -
Irmisch Sandra,
Clavijo McCormick Andrea,
Günther Jan,
Schmidt Axel,
Boeckler Gerhard Andreas,
Gershenzon Jonathan,
Unsicker Sybille B.,
Köllner Tobias G.
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12711
Subject(s) - chemistry , nitrile , cytochrome p450 , populus trichocarpa , enzyme , biochemistry , organic chemistry , gene , genome
Summary 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 CYP 79 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, CYP 71B40v3 and CYP 71B41v2, 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.