Botrytis cinerea Perturbs Redox Processes as an Attack Strategy in Plants

Electron transport processes play vital roles in the functioning of biological systems, and oxygen is the driving force for many of these reactions. A consequence of this is the production of several oxygen-derived molecules, known as active oxygen species (AOS), whose reactivity is greater than that of oxygen itself. There is increasing evidence that Botrytis cinerea exploits the production of AOS in colonising plant tissues, and this is reviewed in the present chapter. Specific considerations are given to the interactions between hydrogen peroxide and other AOS that are produced by the fungus and the plantbased antioxidant systems in determining the outcome of the infection process. In addition, biochemical processes that appear to be of importance for lesion development are discussed and the evidence to support them critically evaluated. These are considered in separate sections dealing with the perturbation of the free radical chemistry and transition metal redox processes (particularly those involving iron), the regulation of enzymes (of both plant and fungal origin), the production of toxic metabolites in the host, and host signalling and programmed cell death. Attention is also drawn to the need for the scientific community to adopt standard procedures (both chemical and biological) to facilitate comparison between results from different groups. Finally, consideration is given to strategies that could be used to resolve some of the outstanding questions relating to our understanding of the Botrytis infection process.