Sensing stress responses in potato with whole-plant redox imaging

Abstract

Environmental stresses are among the major factors that limit crop productivity and plant growth. Plant exposure to various abiotic stress, such as drought, cold temperatures, or high light, results in overproduction of reactive oxygen species (ROS). To avoid oxidative damage, critical mechanisms for their detoxification have evolved, consisting of ROS-scavenging enzymes and small antioxidant molecules, such as glutathione (GSH) and ascorbate. Thus, monitoring redox changes with high spatial and temporal resolution is critical for understanding oxidative stress signaling and has the potential to enable early detection of stress responses in crop plants. In this work, potato plants ( Solanum tuberosum) expressing a chloroplast-targeted reduction-oxidation-sensitive green fluorescent protein2 (roGFP2) were generated to report the redox potential of the glutathione (EGSH) in the chloroplast stroma. By applying whole-plant fluorescence imaging, we mapped alteration in the chloroplast EGSH under several stress conditions including, high-light, cold and drought. Extremely high increase in chloroplast EGSH was observed under the combination of high-light and low temperatures, conditions that specifically induce PSI photoinhibition. Intriguingly, whole-plant ratiometric imaging analysis noted a higher reduced state in newly developed as compared to mature leaves, suggesting a graded stress sensitivity as part of the plant strategies for coping with stress conditions. The presented observations suggest that whole-plant redox imaging can serve as a powerful tool for the basic understanding of plant stress responses as well as for applied agricultural research, such as improving phenotyping capabilities in breeding programs and early detection of stress responses in the field.