Involvement of poly(ADP-ribose)ylation (PARylation) in the regulation of antioxidant defense system in Arabidopsis thaliana under salt stress

: Posttranslational modifications (PTM) are one of the first responses of plants to environmental stress and involve changing the location and activity of proteins in the cell. Addition of poly(ADP-ribose) (PAR) to proteins, poly(ADP-ribose)ylation (PARylation), is a posttranslational modification resulting from the binding of ADP-ribose from NAD + to target proteins by PAR polymerases (PARP). PARylation is involved in many physiological events in plants including abiotic and biotic stress response. The aim of this work was to understand involvement of PARylation in inducing enzymatic antioxidant defence and alternative electron sinks in response to salinity. For this purpose A. thaliana plants were treated with 3-aminobenzamide (3-AB), which is a PARP inhibitor, in the presence of 100 mM NaCl. The 3-AB treatment induced plant fresh weight under control and salinity conditions. Moreover, 100 mM NaCl + 3-AB treated plants had lower lipid peroxidation when compared to 100 mM NaCl group indicating mitigation of oxidative stress. This oxidative stress mitigation was achieved by significantly induced superoxide dismutase (SOD) activity and transcriptional activation of genes related to ROS scavenging such as MSD1 , CAT1 , APX1 , GR1 . On the other hand, transcriptional regulation of mitochondrial alternative oxidase (AOX) pathway was also induced with 3-AB treatment ( AOX1a and AOX1d ) under salt stress indicating that ROS avoidance mechanisms are also activated along with ROS scavenging. However, in contrast to AOX, chloroplastic plastid terminal oxidase pathway was not induced with 3-AB.