Phytoalexin

Article By:

Yazaki, Kazufumi Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan.

Last reviewed:January 2021

DOI:https://doi.org/10.1036/1097-8542.514850

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• Phytoalexins, published June 2014:Download PDF Get Adobe Acrobat Reader

A natural substance that is toxic to microbial pathogens and is synthesized by plants as a defensive response to infection. Phytoalexins comprise an important group of natural compounds manufactured by plants in response to pathogenic intrusions (Fig. 1). In general, plants have various defense mechanisms against attacks by pathogens from their surrounding environment. Upon the invasion of pathogens, a set of quick responses occurs in plant cells, for example, an influx of calcium into the cytosol and a release of anions; then, these signals are transmitted to NADPH oxidase (an enzyme complex) to produce the superoxide anion, which acts as a further signal to induce various defense responses. Production of antifungal and antibacterial compounds by plant cells represents one of these defense responses. These organic compounds are designated as phytoalexins (from the Greek phyton = plant; alexein = to defend or ward off). The accumulation of phytoalexins is an early defense caused by the rapid induction (in a few hours) of a set of biosynthetic genes, which follows the very rapid hypersensitive cell death that can occur in minutes after recognition of pathogens. See also: Chemical ecology; Pathogen; Plant communication; Plant pathology

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