Volatile compound biosynthesis by green leaves from an Arabidopsis thaliana hydroperoxide lyase knockout mutant.

The degradation of polyunsaturated fatty acids through the lipoxygenase pathway is responsible for the production of volatile compounds that confer green sensory notes to the aroma of fruits and vegetables. The peroxidation of free linoleic or linolenic acid by action of lipoxygenase and then the lysis of the resulting hydroperoxides, through a reaction catalyzed by the hydroperoxide lyase, are the most determinant steps of this pathway. This work analyzes the impact of the hydroperoxide lyase depletion on the volatile composition of leaves from Arabidopsis thaliana that is used as model system. The work involves the characterization of the volatile profiles of the Arabidopsis plants followed by a study of the metabolism of radio-labeled linoleic acid and determinations of lipoxygenase activity. Hydroperoxide lyase-knockout plants show similar levels of C6 compounds, but the total amount of C5 compounds is 4-fold higher in mutant plants. The perspectives of production of vegetable products with a modified aroma by genetically engineering the lipoxygenase pathway were discussed with respect to the statistical results.