Importance of Reactive Oxygen Species in Plants-Pathogens Interactions

Plant pathogens have developed various independent and well-elaborated mech-anisms of penetrating and accessing plant cell contents. The production of reac-tive oxygen species (ROS) by the consumption of molecular oxygen during host–pathogen interactions is termed the oxidative burst. The most important ROS are singlet oxygen, the hydroxyperoxyl radical, the superoxide anion, hydrogen per-oxide, the hydroxyl radical and the closely related reactive nitrogen species, nitric oxide. There are profound differences between monocots and dicots as well as in the biology of biotrophic, hemibiotrophic and necrotrophic pathogens. ROS acts synergistically in a signal amplification to drive the hypersensitive reaction (HR) and the establishment of systemic defenses. The role of ROS in successful path-ogenesis, it is important to try to inhibit the cell death machinery selectively and simultaneously to monitor other defense and pathogenesis-related events. With the understanding of the molecular mechanisms underlying the localized activa-tion of the oxidative burst following perception of pathogen avirulence signals and key downstream responses including gene activation, cell death, and long-distance signaling, novel strategies will be developed for engineering enhanced protection against pathogens by manipulation of the oxidative burst and oxidant-mediated signal pathways. In this review, it is assessed the different roles of ROS in host–pathogen interactions with special emphasis on plant pathogens.