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Plants are under a continuous influence of biotic and abiotic stresses. As a defense against motile herbivores, many plants as well as the tree model organism Populus trichocarpa emit a complex blend of volatile compounds. These volatile compounds comprise terpenes, green leaf volatiles (GLV´s), nitrogenous compounds and aromatic compounds. Defense compounds like volatile alcohols reduce the fitness of the herbivore on the emitting plant as they lure herbivore enemies.

Recently we identified several enzymes responsible for the formation of volatile alcohols in poplar. L-phenylalanine can be converted by several CYP79 enzymes to benzyl cyanide with phenylacetaldoxime as an intermediate. RNAi-meidated knock-down of the responsible CYP79 enzymes resulted not only in the reduction of phenylacetaldoxime and benzyl cyanide in the volatile blend, but also the reduction in the amount of emitted 2-phenylethanol could be observed. The feeding of labeled phenylacetaldoxime resulted in the emission of the labeled benzyl cyanide, 2-phenylacetaldehyde and 2-phenylethanol, leading to a pathway that connects these herbivore induced volatiles. In aim of unraveling the enzymatic reactions involved in this putative pathway, we identified a nitrilase (PtNIT1) that converts benzyl cyanide to phenylacetic acid, which might be further reduced to 2-phenylacetaldehyde and could be oxidized to 2-pehnylethanol by aldehyde reductases (PtPAR1, 2, 4, 5).

Interestingly these aldehyde reductases seem to be able to convert fatty acid derived aldehydes like nonanal and the monoterpenes citral and citronellal to the corresponding alcohols.

In my PhD-Thesis I want to identify these biosynthesis pathways of volatile alcohols that will lead us to a better understanding of plant defense and improvements in pest control.
last updated on 2019-06-13