The importance of lipoxygenase control in the production of green leaf volatiles by lipase-dependent and independent pathways

Abstract

Green leaf volatiles (GLVs) are six-carbon volatile compounds. They are formed from fatty acids by a dioxygenation reaction catalyzed by lipoxygenase and a subsequent cleavage reaction catalyzed by hydroperoxide lyase. GLVs are involved in direct and indirect plant defense against herbivores and pathogens. In intact plant tissues, GLVs are usually present at low concentrations, but upon wounding, GLVs are synthesized rapidly: within seconds to minutes. It has been hypothesized that this ‘GLV burst’ is supported by activation of pre-existing enzymes on endogenous substrates; however, the detailed mechanism of the GLV burst has not been elucidated. Recently, we found that a certain portion of GLVs is formed without liberation of free fatty acids from lipids. Accordingly, we hypothesized that lipoxygenase plays an essential role in the GLV burst. In particular, direct oxygenation by lipoxygenase on membrane lipids seems to be responsible. Lipoxygenase is also a target for controlling GLV levels in food derived from plants.