Singlet oxygen in plants: production, detoxification and signaling

Singlet oxygen (O-1(2)) is a singular reactive oxygen species (ROS) that is produced constitutively in plant leaves in light via chlorophylls that act as photosensitizers. This O-1(2) production is spatially resolved within thylakoid membranes and is enhanced under light stress conditions. O-1(2) can also be produced by phytotoxins during plant-pathogen interactions. O-1(2) is highly reactive, can be toxic to cells and can be involved in the signaling of programmed cell death or acclimation processes. Here, we summarize current knowledge on O-1(2) management in plants and on the biological effects of this peculiar ROS. Compared with other ROS, O-1(2) has received relatively little attention, but recent developments indicate that it has a crucial role in the responses of plants to light.