Dissection of 12-oxophytodienoic acid (OPDA) functions in plant physiology by use of a library of OPDA-derivatives

• Applicant: Professor Dr. Karl-Josef Dietz
• Subject Area: Plant Biochemistry and Biophysics ; Plant Physiology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 468843036

Lipid oxidation products play an important role in regulating acclimatization and development. 12-cis-oxophytodienoic acid (OPDA) forms in plants from alpha-linolenic acid enzymatically and plays roles as precursor of the plant hormone jasmonic acid, as ligand of cyclophilin 20-3 (CYP20-3) in the regulation of cell redox homeostasis, and as reactive carbonyl binding to protein thiols and also glutathione. The project is planned to exploit a novel and thus unique library of OPDA derivatives, developed in the last funding period. The library comprises 13 compounds with distinct effects on biochemical and physiological processes with relevance in OPDA-dependent signalling. Some derivatives display a similar or even stronger effect than OPDA, other lack effectiveness, and this pattern of effectiveness differs from one process under investigation to another. The hypothesis underlying the proposal is that the library constitutes a unique toolset that allows researchers to differentiate OPDA-dependent signalling pathways and acclimatization reactions in vitro and in planta. The project focuses on excess excitation energy acclimatization, stomatal closure and wounding. We will test the hypothesis using the response of identified marker transcripts as readout. The project also explores uptake and fate of selected derivatives in the plant cell. The atomic structure of the receptor of OPDA identified first, namely CYP20-3, will be addressed by x-ray and NMR-based structural analysis and complemented by molecular modelling. Here the focus is the elucidation of the binding features of OPDA and of selected derivatives. The second part of the project addresses OPDA-addition to protein thiols, a process we have termed OPDAylation, which is suggested to represent a regulatory posttranslational modification. Using proteomics approaches, we will search for OPDAylated proteins in cellulo. In addition to the OPDA addition, we will investigate the process of de-OPDAylation, i.e. the release of OPDA from OPDAylated proteins. During the previous funding period, we revealed a slow de-OPDAylation in the presence of physiological concentrations of glutathione. The hypothesis is that enzymes accelerate the process of de-OPDAylation in plant cells, and to this end we will use targeted and untargeted approaches to identify these enzymes. The entire project is expected to deliver independent mechanistic and fundamental insight to the current controversial debate on the function of OPDA in plant acclimatization and development.

• DFG Programme: Research Grants