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A Putative Role for Fusaric Acid in Biocontrol of the Parasitic Angiosperm Orobanche ramosa

May 2006 , Volume 19 , Number  5
Pages  550 - 556

Brahim Bouizgarne , 1 , 2 , 3 Hayat El-Maarouf-Bouteau , 4 Karine Madiona , 1 Bernadette Biligui , 1 Michèle Monestiez , 1 Anne Marie Pennarun , 1 Zahia Amiar , 1 Jean Pierre Rona , 1 Yedir Ouhdouch , 3 Ismaïl El Hadrami , 2 and François Bouteau 1

1LEM (EA 3514), Université Paris 7, 2, place Jussieu, 750251 Paris cedex 05, France; 2Laboratoire de Physiologie Végétale, Equipe Biotechnologies et Physiologie Végétales, Faculté des Sciences-Semlalia, B.P. 2390, 40001 Marrakech, Maroc; 3Laboratoire de Microbiologie, Faculté des Sciences-Semlalia, B.P. 2390, 40001 Marrakech, Maroc; 4Laboratoire de Parasitologie Végétale, UPMC, 3, rue Galilée, 94200 Ivry sur Seine, France

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Accepted 9 January 2006.

Fusarium spp. are ubiquitous fungi found in soil worldwide as both pathogenic and nonpathogenic strains. The signals leading to disease or the absence of disease are poorly understood. We recently showed that fusaric acid (FA), a nonspecific toxin produced by most Fusarium spp., could elicit various plant defense responses at 100 nM without toxic effect. In this study, we checked for the effect of FA on root and root hairs, probable first site of contact between the fungi and the host. Large FA concentrations reduce root and root-hair growth and induce a rapid transient membrane hyperpolarization, followed by a large depolarization, due to the inhibition of H+-ATPase currents. Nanomolar concentrations of FA induced only an early transient membrane hyperpolarization of root hairs compatible with the induction of a signal transduction pathway. FA at 10-7 M failed to induce salicylic acid- and jasmonic acid/ethylene-dependent defense-related genes but inhibited the germination of the angiosperm parasite Orobanche ramosa in contact of FA-pretreated Arabidopsis thaliana seedlings. These data suggest that FA at nontoxic concentrations could activate signal transduction components necessary for plant-defense responses that could contribute to biocontrol activity of Fusarium spp.

Additional keyword: ion fluxes.

The American Phytopathological Society, 2006