Contribution of proline metabolism to the control of cellular redox homeostasis under biotic stress in Arabidopsis

CISLAGHI AP,; ALVAREZ ME

Mendoza

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2023

SAIB

To survive under stress conditions, plants must activate stress-specific signaling pathways that generate biochemical, physiologicaland morphological changes allowing adaptation. Proline (Pro) metabolism influences the cellular redox homeostasis in differentways. Pro dehydrogenase (ProDH) is a mitochondrial enzyme regulating the limiting step in Pro catabolism. In animals, this enzymeaffects lifespan extension, apoptosis, tumor suppression, and cell survival. In Arabidopsis, ProDH promotes ROS production duringactivation of the hypersensitive response. Arabidopsis ProDH is encoded by two genes, AtProDH1 and AtProDH2 that are inducedduring plant-pathogen interactions. Both isoforms potentiate the activity of the plant plasma membrane NADPH oxidase, alsoknown as respiratory burst oxidase homolog (RBOH). Under biotic stress conditions, RBOHD is responsible for apoplastic ROS(aROS) accumulation triggered by flg22 (22 amino acid peptide derived from bacterial flagellin) treatment. We are investigatinghow mitochondrial ProDH affects the activity of plasma membrane RBOHD. In particular, we are studying whether this is mediatedby alterations of cytosolic redox homeostasis. We used a sensitive fluorimetry method to detect variations in the Grx1-roGFP2protein acting as a glutathione redox potential sensor in Arabidopsis leaf discs. We detected clear changes in cytoplasmicglutathione redox dynamics upon flg22 perception. This involves a sustained oxidation of Grx1-roGFP2 that succeeds the transientaROS burst measured by luminol assay. Inhibition of ProDH reduced flg22-induced Grx1-roGFP2 oxidation in cytosol. AsGSH/GSSG homeostasis is sensitive to the NADPH/NADP changes, we are evaluating how mitochondrial ProDH affects thecytoplasmic NADPH/NADP ratio. Interestingly, AtProDH1 and AtProDH2 would mediate this effect by acting in different leaftissues.