Int. J. Mol. Sci. 2009, 10(8), 3371-3399; doi:10.3390/ijms10083371
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Chemical Diversity and Defence Metabolism: How Plants Cope with Pathogens and Ozone Pollution

Università degli Studi di Milano, Dipartimento di Produzione Vegetale, Sezione di Patologia Vegetale, Via Celoria 2, 20133 Milano, Italy
* Author to whom correspondence should be addressed.
Received: 6 June 2009; in revised form: 24 July 2009 / Accepted: 29 July 2009 / Published: 30 July 2009
(This article belongs to the Special Issue Biotic and Abiotic Stress)
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Abstract: Chemical defences represent a main trait of the plant innate immune system. Besides regulating the relationship between plants and their ecosystems, phytochemicals are involved both in resistance against pathogens and in tolerance towards abiotic stresses, such as atmospheric pollution. Plant defence metabolites arise from the main secondary metabolic routes, the phenylpropanoid, the isoprenoid and the alkaloid pathways. In plants, antibiotic compounds can be both preformed (phytoanticipins) and inducible (phytoalexins), the former including saponins, cyanogenic glycosides and glucosinolates. Chronic exposure to tropospheric ozone (O3) stimulates the carbon fluxes from the primary to the secondary metabolic pathways to a great extent, inducing a shift of the available resources in favour of the synthesis of secondary products. In some cases, the plant defence responses against pathogens and environmental pollutants may overlap, leading to the unspecific synthesis of similar molecules, such as phenylpropanoids. Exposure to ozone can also modify the pattern of biogenic volatile organic compounds (BVOC), emitted from plant in response to herbivore feeding, thus altering the tritrophic interaction among plant, phytophagy and their natural enemies. Finally, the synthesis of ethylene and polyamines can be regulated by ozone at level of S-adenosylmethionine (SAM), the biosynthetic precursor of both classes of hormones, which can, therefore, mutually inhibit their own biosynthesis with consequence on plant phenotype.
Keywords: stress physiology; secondary metabolism; phytochemicals; phytoalexins; phytoanticipins; tropospheric ozone pollution; volatile organic compounds

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MDPI and ACS Style

Iriti, M.; Faoro, F. Chemical Diversity and Defence Metabolism: How Plants Cope with Pathogens and Ozone Pollution. Int. J. Mol. Sci. 2009, 10, 3371-3399.

AMA Style

Iriti M, Faoro F. Chemical Diversity and Defence Metabolism: How Plants Cope with Pathogens and Ozone Pollution. International Journal of Molecular Sciences. 2009; 10(8):3371-3399.

Chicago/Turabian Style

Iriti, Marcello; Faoro, Franco. 2009. "Chemical Diversity and Defence Metabolism: How Plants Cope with Pathogens and Ozone Pollution." Int. J. Mol. Sci. 10, no. 8: 3371-3399.

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