Spatial dependence for hydrogen peroxide-directed signaling in light-stressed plants.

In this article, the role of the reactive oxygen species (ROS) hydrogen peroxide (H2O2) as a signaling molecule involved in plant response to a sudden change in light intensity will be considered in a spatial context. The relatively low reactivity of H2O2 compared with other ROS (Halliwell and Gutteridge, 1985) might suggest that it could diffuse from a site of production to initiate intracellular and systemic signaling (Mullineaux and Karpinski, 2002). However, another view is promulgated here that allows for compartment-specific H2O2-mediated signaling associated with acclimation to high light. It is proposed that a spatial component to signaling is maintained by limiting the accumulation of H2O2 to its sites of production. This would allow H2O2 to initiate distinct signals depending on its subcellular origin (Mullineaux and Karpinski, 2002). Conversely, breakdown in the integrity of this spatial component, such that H2O2 diffuses into other subcellular compartments, would promote oxidative stress and trigger signaling associated with cell death.