Regulation of synthesis and function of 12-oxophytodienoic acid in plant cell signaling

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12-Oxophytodienoic acid (OPDA) is a C18-oxylipin synthesized in the chloroplast from alpha linolenic acid. OPDA functions in cell signaling for metabolic regulation and stress acclimation and as precursor of jasmonic acid synthesis. As joint effort of two groups with expertise in plant stress acclimation and bioorganic synthesis, we plan addressing the signaling and regulatory function of OPDA as ligand and reactive carbonyl species. We will explore the regulation of 13-lipoxygenases catalyzing the primary committed step of the pathway and the likely interaction of the three pathway enzymes in a supramolecular complex for substrate channeling of labile intermediates. The development of an efficient biosynthetic route for OPDA synthesis in gram amounts, and the possibility to construct a library of OPDA derivatives as free acids or more lipophilic ethylesters will enable realizing novel strategies in planta and in vitro. The project shall scrutinize the function of OPDA in comparison to the derived reduced cyclopentanone derivative 3-oxo-2(2’-pentenyl) cyclopentane-1-octanoic acid (OPC-8:0) devoid of the reactive alpha/beta-unsaturated carbonyl moiety and the ethylester which cannot be processed to jasmonic acid. Using these tools we will identify and characterize OPDA and OPC-8:0 binding partners, and screen for OPDAylation as posttranslational modification possibly involved in regulating metabolism versus defense. The four hypotheses of the project are based on established knowledge and own published and preliminary work and are expected to unravel novel mechanisms of OPDA function in plant cell acclimation.