Stimulatory effect of salicylic acid on Polyamine oxidase activity in Thymus daenensis L. callus

According to previous studies, salicylic acid decreases the hyperhydricity in Thymus daenesis and this event might be due to the effect on polyamines metabolism. Polyamine oxidase enzyme catabolizes the polyamines in the cell and one of its byproducts is hydrogen peroxide (H2O2). Purpose of this study is analyses of salicylic acid effect on polyamine oxidase activity in thymus daenensis callus. In this study, the activity of polyamine oxidase, content of H2O2, and responses of enzymatic antioxidant including catalase and peroxidase was measured. Results showed that salicylic acid (concentrations of 10 and 20 µM) caused an increase in polyamine oxidase activity in a dose dependent manner. In callus under salicylic acid treatment (20 µM) a decrease in soluble peroxidase activity and an elevated H2O2 content was observed. Increase of H2O2 might be due to the influence of salicylic acid on polyamine oxidase and peroxidase activities. While variations in H2O2 levels resulted in no changes of catalase activity. Regulation of H2O2 level by salicylic acid through its effect on polyamine oxidase activity might contribute to ROS homeostasis, which is necessary for in vitro developmental processes in plant cells.