The N icotiana attenuata GLA1 lipase controls the accumulation of P hytophthora parasitica-induced oxylipins and defensive secondary metabolites.

N icotiana attenuata plants silenced in the expression of GLYCEROLIPASE A1 (ir- gla1 plants) are compromised in the herbivore- and wound-induced accumulation of jasmonic acid ( JA). However, these plants accumulate wild-type ( WT) levels of JA and divinyl-ethers during P hytophthora parasitica infection. By profiling oxylipin-enriched fractions with targeted and untargeted liquid chromatography-tandem time-of-flight mass spectrometry approaches, we demonstrate that the accumulation of 9-hydroxy-10 E,12 Z-octadecadienoic acid (9- OH-18:2) and additional C₁₈ and C₁₉ oxylipins is reduced by ca. 20-fold in P . parasitica-infected ir- gla1 leaves compared with WT. This reduced accumulation of oxylipins was accompanied by a reduced accumulation of unsaturated free fatty acids and specific lysolipid species. Untargeted metabolic profiling of total leaf extracts showed that 87 metabolites accumulated differentially in leaves of P . parasitica-infected ir- gla1 plants with glycerolipids, hydroxylated-diterpene glycosides and phenylpropanoid derivatives accounting together for ca. 20% of these 87 metabolites. Thus, P . parasitica-induced oxylipins may participate in the regulation of metabolic changes during infection. Together, the results demonstrate that GLA1 plays a distinct role in the production of oxylipins during biotic stress responses, supplying substrates for 9- OH-18:2 and additional C₁₈ and C₁₉ oxylipin formation during P . parasitica infection, whereas supplying substrates for the biogenesis of JA during herbivory and mechanical wounding. [ABSTRACT FROM AUTHOR]