RESUMEN
Plant cells produce reactive oxygen species (ROS) as by-products of oxygen metabolism and for signal transduction. Depending on their concentration and their site of production, ROS can cause oxidative damage within the cell and must be effectively scavenged. Detoxification of the most stable ROS, hydrogen peroxide (H2O2), via the glutathione-ascorbate pathway may transiently alter the glutathione redox potential (EGSH). Changes in EGSH can thus be considered as an indicator of the oxidative load in the cell. Genetically encoded probes based on roGFP2 enable extended opportunities for in vivo monitoring of H2O2 and EGSH dynamics. Here, we provide detailed protocols for live monitoring of both parameters in the cytosol with the probes Grx1-roGFP2 for EGSH and roGFP2-Orp1 for H2O2, respectively. The protocols have been adapted for live cell imaging with high lateral resolution on a confocal microscope and for multi-parallel measurements in whole organs or intact seedlings in a fluorescence microplate reader. Elicitor-induced ROS generation is used for illustration of the opportunities for dynamic ROS measurements that can be transferred to other research questions and model systems.