C12 derivatives of the hydroperoxide lyase pathway are produced by product recycling through lipoxygenase-2 in Nicotiana attenuata leaves

Abstract

In response to diverse stresses, the hydroperoxide lyase (HPL) pathway produces C6 aldehydes and 12-oxo-(9Z)-dodecenoic acid ((9Z)-traumatin). Since the original characterization of (10E)-traumatin and traumatic acid, little has been added to our knowledge of the metabolism and fluxes associated with the conversion of (9Z)-traumatin into diverse products in response to wounding and herbivory. A liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method was developed to quantify C12 derivatives of the HPL pathway and to determine their metabolism after wounding and simulated herbivory in Nicotiana attenuata leaves. Ninety-eight per cent of the (9Z)-traumatin produced was converted to 9-hydroxy-(10E)-traumatin (9-OH-traumatin); two-thirds by product recycling through lipoxygenase-2 (NaLOX2) activity and one-third by nonenzymatic oxidation. Thirty-eight per cent of the de novo produced 9-OH-traumatin was conjugated to glutathione, consistent with this oxylipin being a reactive electrophile species. 12-OH-(9Z)-dodecenoic and dodecenedioic acids also showed rapid increases after wounding and simulated herbivory and a role for C12 derivatives as signals in these processes was consistent with their ability to elicit substantial changes in gene expression. These results underscore the importance of metabolite reflux through LOX2, an insight which creates new opportunities for a functional understanding of C12 derivatives of the HPL pathway in the regulation of stress responses. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.