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Keywords:

  • herbivory;
  • hydroperoxide lyase (HPL);
  • lipoxygenase (LOX);
  • oxylipin;
  • tobacco (Nicotiana attenuata);
  • traumatic acid;
  • traumatin

Summary

  • 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.