RoGFP1 is a quantitative biosensor in maize cells for cellular redox changes caused by environmental and endogenous stimuli

Reduction-oxidation-sensitive green fluorescent proteins (roGFPs) have been demonstrated to be valuable tools in sensing cellular redox changes in mammalian cells and model plants, yet have not been applied in crops such as maize. Here we report the characteristics of roGFP1 in transiently transformed maize mesophyll protoplasts in response to environmental stimuli and knocked-down expression of ROS-scavenging genes. We demonstrated that roGFP1 in maize cells ratiometrically responds to cellular redox changes caused by H2O2 and DTT, as it does in mammalian cells and model plants. Moreover, we found that roGFP1 is sensitive enough to cellular redox changes caused by genetic perturbation of single ROS genes, as exemplified by knocked-down expression of individual ZmAPXs, in maize protoplasts under controlled culture conditions and under stress conditions imposed by H2O2 addition. These data provide evidence that roGFP1 functions in maize cells as a biosensor for cellular redox changes triggered by genetic lesion of single ROS genes even under stress conditions, and suggest a potential application of roGFP1 in large-scale screening for maize mutants of ROS signaling involved in development and stress resistance.