Environmental stresses often trigger rapid generation of reactive oxygen species (ROS) in plants. Excessive amount of ROS can cause damage to plant cells and thus need to be counteracted by cellular antioxidant systems. On the other hand, ROS also serve as signaling molecules that modulate various physiological responses and developmental processes. Signaling function of ROS is largely achieved through oxidative modifications of redox-sensitive proteins. Therefore, development of methods for high-throughput identification of redox-sensitive proteins and for verifying and characterizing their in vivo redox states is essential for advancing our understanding of ROS-mediated signaling pathways.