phytoalexin


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Phytoalexin

Any antibiotic produced by plants in response to microorganisms. Plants use physical and chemical barriers as a first line of defense. When these barriers are breached, however, the plant must actively protect itself by employing a variety of strategies. Plant cell walls are strengthened, and special cell layers are produced to block further penetration of the pathogen. These defenses can permanently stop a pathogen when fully implemented, but the pathogen must be slowed to gain time.

The rapid defenses available to plants include phytoalexin accumulation, which takes a few hours, and the hypersensitive reaction, which can occur in minutes. The hypersensitive reaction is the rapid death of plant cells in the immediate vicinity of the pathogen. Death of these cells is thought to create a toxic environment of released plant components that may in themselves interfere with pathogen growth, but more importantly, damaged cells probably release signals to surrounding cells and trigger a more comprehensive defense effort. Thus, phytoalexin accumulation is just one part of an integrated series of plant responses leading from early detection to eventual neutralization of a potentially lethal invading microorganism.

The tremendous capacity of plants to produce complex chemical compounds is reflected in the structural diversity of phytoalexins. Each plant species produces one or several phytoalexins, and the types of phytoalexins produced are similar in related species. The diversity, complexity, and toxicity of phytoalexins may provide clues about their function. The diversity of phytoalexins may reflect a plant survival strategy. That is, if a plant produces different phytoalexins from its neighbors, it is less likely to be successfully attacked by pathogens adapted to its neighbor's phytoalexins. Diversity and complexity, therefore, may reflect the benefits of using different deterrents from those found in other plants. See Plant pathology

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.

phytoalexin

[′fīd·ȯ·ə′lek·sən]
(biochemistry)
A natural substance that is toxic to fungi and is synthesized by a plant as a response to fungal infection.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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References in periodicals archive ?
It can be assumed that the phytoalexins are localized in the tissue beneath and close to the site of fungal or bacterial infection (Bennett & Wallsgrove, 1994).
Phytoalexin indution in french bean: intercellular transmission of elicitation in cell suspension cultures and hypocotyl sections of Phaseolus vulgaris.
Especially, the fraction with Mw in the range of 1-3 kDa of oligoalginate (separated from irradiated alginate) and oligochitosan (separated from irradiated chitosan) was presumed to contain effective compounds for the growth promotion, to enhance activity of phytoalexin enzymes, and to increase the yield of crop plants [12, 23].
Ausubel, "Mode of action of the Arabidopsis thaliana phytoalexin camalexin and its role in Arabidopsis-pathogen interactions," Molecular Plant-Microbe Interactions, vol.
Numerous studies showed UV treatment can stimulate synthesis of phytoalexin which are antimicrobial compounds contributing in disease resistance [15, 16].
Okada et al., "Stemar-13-ene synthase, a diterpene cyclase involved in the biosynthesis of the phytoalexin oryzalexin S in rice," FEBS Letters, vol.
Resveratrol is a stilbene compound and a phytoalexin. It is abundantly present in red wine, berries, red grapes, blueberries, peanuts, teasadori, hops, pistachios and grape juice, and cranberry.
Bonnesen, "A review of the content of the putative chemopreventive phytoalexin resveratrol in red wine," Food Chemistry, vol.
Zhang, "Resveratrol, a polyphenol phytoalexin, protects against doxorubicin-induced cardiotoxicity," Journal of Cellular and Molecular Medicine, vol.
RESV is a phytoalexin, a normal constituent of the plant cell produced by plants in response to fungal/bacterial insult, stress, or elicitor treatment [7].
The antifungal action of plant defensin could be linked with synthesis of phytoalexin and lignin due to induction of systemic resistance in plants.