Mechanisms for the generation of reactive oxygen species in plant defence response

Abstract

Recent data indicate that plants, in a manner similar to the situation found in mammalian phagocytotic cells, produce reactive oxygen species (ROS) in response to pathogen infection. This reaction could be very quick when using pre-existing, usually exocellular, components and/or, when biochemical machinery of the cell is activated, relatively late and long-lasting. The oxidative burst is defined as a rapid, transient production of high levels of ROS in response to external stimuli. Two major models depicting the origin of ROS in the oxidative burst are described, namely: the NADPH oxidase system and the pH-dependent generation of hydrogen peroxide by exocellular peroxidases. Additionally, the participation of exocellular ROS-generating enzymes, like germin-like oxalate oxidases and amine oxidases, in plant defence response is demonstrated. The involvement of protoplasmic ROS-generating systems is also indicated.