Hydrogen peroxide functions as a stress signal in plants

Plants have evolved complex regulatory mechanisms in adapting to various environmental stresses. One of the consequences of many stresses is an increase in the cellular concentration of reactive oxygen species (ROS), which are subsequently converted to hydrogen peroxide (H2O2). An oxidative burst caused by biotic or abiotic stress leads to a disturbance in the cellular redox balance and is highly toxic to cells. Recently, H2O2, in addition to being a toxicant, has been regarded as a signaling molecule and a regulator of the expression of some genes in cells. These include genes encoding antioxidants, cell rescue/defense proteins, and signaling proteins such as kinase, phosphatase, and transcription factors. Here, we review the function of H2O2 as a signal molecule in the transduction of stress signals to the alteration of expression profiles of target genes, and we summarize the evidence that H2O2 acts as a stress signal in plants