Two herbivore-induced cytochrome P450 enzymes CYP79D6 and CYP79D7 catalyze the formation of volatile aldoximes involved in poplar defense.
Aldoximes are known as floral and vegetative plant volatiles but also as biosynthetic intermediates for other plant defense compounds. While the cytochrome P450 monooxygenases (CYP) from the CYP79 family forming aldoximes as biosynthetic intermediates have been intensively studied, little is known about the enzymology of volatile aldoxime formation. We characterized two P450 enzymes, CYP79D6v3 and CYP79D7v2, which are involved in herbivore-induced aldoxime formation in western balsam poplar (Populus trichocarpa). Heterologous expression in Saccharomyces cerevisiae revealed that both enzymes produce a mixture of different aldoximes. Knockdown lines of CYP79D6/7 in gray poplar (Populus × canescens) exhibited a decreased emission of aldoximes, nitriles, and alcohols, emphasizing that the CYP79s catalyze the first step in the formation of a complex volatile blend. Aldoxime emission was found to be restricted to herbivore-damaged leaves and is closely correlated with CYP79D6 and CYP79D7 gene expression. The semi-volatile phenylacetaldoxime decreased survival and weight gain of gypsy moth (Lymantria dispar) caterpillars, suggesting that aldoximes may be involved in direct defense. The wide distribution of volatile aldoximes throughout the plant kingdom and the presence of CYP79 genes in all sequenced genomes of angiosperms suggest that volatile formation mediated by CYP79s is a general phenomenon in the plant kingdom.
Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
Sandra
S
Irmisch
Andrea Clavijo
AC
McCormick
G Andreas
GA
Boeckler
Axel
A
Schmidt
Michael
M
Reichelt
Bernd
B
Schneider
Katja
K
Block
Jörg-Peter
JP
Schnitzler
Jonathan
J
Gershenzon
Sybille B
SB
Unsicker
Tobias G
TG
Köllner
D000438:Alcohols / Q000378:metabolism; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D018745:Genome, Plant; D060434:Herbivory; D009026:Mortality; D009036:Moths / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D009570:Nitriles / Q000378:metabolism; D010091:Oximes / Q000378:metabolism / Q000494:pharmacology; D010649:Phenylalanine / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D032107:Populus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D055549:Volatile Organic Compounds / Q000032:analysis / Q000378:metabolism*
D000438:Alcohols; D009570:Nitriles; D010091:Oximes; D010940:Plant Proteins; D055549:Volatile Organic Compounds; D010649:Phenylalanine; C408881:phenylacetaldoxime; D003577:Cytochrome P-450 Enzyme System