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

ANA CISLAGHI; MARIA ELENA ALVAREZ

Mendoza, Argentina

Congreso; LVIII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología molecular; 2022

To survive under stress conditions, plants must activate stress-specific signaling pathways, which finally lead to biochemical, physiological and morphological changes to adapt to adverse environments. Proline (Pro) metabolism influences the cellular redox homeostasis in different ways. Pro dehydrogenase (ProDH) is a mitochondrial enzyme regulating the limiting step in Pro catabolism. In animals, this enzyme affects lifespan extension, apoptosis, tumor suppression, and cell survival. In Arabidopsis, ProDH promotes ROS production during activation of the hypersensitive response. Arabidopsis ProDH is encoded by two genes, AtProDH1 and AtProDH2 that are induced during plant-pathogen interactions. Both isoforms potentiate the activity of the plant plasma membrane NADPH oxidase, also known 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 investigating how mitochondrial ProDH affects the activity of plasma membrane RBOHD. In particular, we are studying whether this is mediated by alterations of cytosolic redox homeostasis. We used a sensitive fluorimetry method to detect variations in the Grx1-roGFP2 protein acting as a glutathione redox potential sensor in Arabidopsis leaf discs. We detected clear changes in cytoplasmic glutathione redox dynamics upon flg22 perception. This involves a sustained oxidation of Grx1-roGFP2 that succeeds the transient aROS burst measured by luminol assay. Inhibition of ProDH reduced flg22-induced Grx1-roGFP2 oxidation in cytosol. As GSH/GSSG homeostasis is sensitive to the NADPH/NADP changes, we are evaluating how mitochondrial ProDH affects the cytoplasmic NADPH/NADP ratio. Interestingly, AtProDH1 and AtProDH2 would mediate this effect by acting in different leaf tissues.