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

12-氧代植物二烯酸(OPDA)是由α-亚麻酸在叶绿体中合成的一种C18-氧基脂。OPDA在新陈代谢调节和压力适应的细胞信号传递中发挥作用，也是茉莉酸合成的前体。作为两个在植物胁迫适应和生物有机合成方面有专长的小组的共同努力，我们计划解决OPDA作为配体和活性羰基物种的信号和调节功能。我们将探索13-脂氧合酶催化该途径的主要步骤的调节，以及在一个超分子复合体中三种途径酶之间可能的相互作用，以促进不稳定中间体的底物通道。开发一条有效的生物合成路线来合成克量的OPDA，以及构建作为游离酸或更亲油的乙酯的OPDA衍生库的可能性，将使在植物和体外实现新的策略成为可能。本项目应将OPDA的功能与衍生的还原环戊酮衍生物3-氧-2(2‘-戊烯基)环戊烷-1-辛酸(OPC-8：0)进行比较，该衍生物不含反应性的α/β-不饱和羰基部分和不能加工成茉莉酸的乙酯。使用这些工具，我们将识别和表征OPDA和OPC-8：0结合伙伴，并筛选OPDA化作为可能参与调节新陈代谢和防御的翻译后修饰。该项目的四个假设是基于已有的知识和自己发表的和初步的工作，有望揭开OPDA在植物细胞驯化中作用的新机制。

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.