ABSTRACT
A number of conditions (referred to as oxidative stress) elicit stress responses in plants due to the formation of active oxygen species (AOS). This chapter gives a brief overview of what is known about the generation and scavenging of AOS in different cellular compartments and under various stress conditions and deals with attempts to enhance the oxidative stress tolerance by generating transgenic plants overproducing antioxidant enzymes. The enzymes overproduced so far include superoxide dismutase, ascorbate peroxidase, glutathione reductase, and glutathione-synthesizing enzymes. In general, the oxidative stress tolerance of transgenic plants was found to be enhanced, at least in model systems, and there are a number of encouraging results concerning enhancement of the tolerance to physiological types of stress. The results are discussed in terms of the contribution of the overproduced enzyme to oxidative stress tolerance, the interaction of this enzyme with suborganellar structures, and with other components of the antioxidant system, and the importance of oxidative stress in various physiological types of stress. We end with a brief summary of recent developments regarding the identification of gene products that may prove to be of importance in defence against oxidative stress.
