Reactive oxygen species and oxidative stress in plants.

Abstract

AbstractPlant oxidative stress is a complex physiological phenomenon. It develops as a result of overproduction of reactive oxygen species (ROS) and accompanies virtually all biotic and abiotic stresses. This chapter aims to update current knowledge of the cellular events relating to oxidative stress in plants. Recent data have clarified the 'origin' of oxidative stress in plants, and show that apart from classical chloroplast, mitochondrial and peroxisome sources, ROS are also produced by NADPH oxidases and peroxidases. These two systems seem to be the primary source of ROS generation in a number of plant stress responses. A recent and important discovery is that ROS signalling is based on the Ca2+-mediated mechanism; this explains how cells can 'read' ROS-encoded message. Although the precise reactions for this mechanism are far from understood, the physiological importance of ROS-Ca2+ signalling as a key 'regulatory hub' has become widely accepted. A number of downstream Ca2+-regulated cascades have been identified in plants, these include regulatory systems with one (e.g. ROS-sensitive ion channels and transcription factors), two (e.g. Ca2+-activated NADPH oxidases and calmodulin) or multiple components (e.g. Ca2+-dependent protein kinases and mitogen-activated protein kinases). A wealth of knowledge has been gathered about the metabolism and damaging action of ROS as well as ROS protective antioxidant mechanisms. Antioxidant systems have been characterized in details at physiological and genetic levels, with the fundamental role of S-containing amino acids as molecular switches being demonstrated. Research into plant oxidative stress has also shown great potential for developing stress-tolerant crops. This can be achieved through the use of directed evolution techniques to prevent protein oxidation, as well as modification of programmed cell death mechanisms and enzymes involved in ROS generation, sensing and scavenging.