Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/195185
Type: Artigo de periódico
Title: Nitric Oxide Synthase-mediated Phytoalexin Accumulation In Soybean Cotyledons In Response To The Diaporthe Phaseolorum F. Sp. Meridionalis Elicitor.
Author: Modolo, Luzia Valentina
Cunha, Fernando Queiroz
Braga, Márcia Regina
Salgado, Ione
Abstract: Phytoalexin biosynthesis is part of the defense mechanism of soybean (Glycine max) plants against attack by the fungus Diaporthe phaseolorum f. sp. meridionalis (Dpm), the causal agent of stem canker disease. The treatment of soybean cotyledons with Dpm elicitor or with sodium nitroprusside (SNP), a nitric oxide (NO) donor, resulted in a high accumulation of phytoalexins. This response did not occur when SNP was replaced by ferricyanide, a structural analog of SNP devoid of the NO moiety. Phytoalexin accumulation induced by the fungal elicitor, but not by SNP, was prevented when cotyledons were pretreated with NO synthase (NOS) inhibitors. The Dpm elicitor also induced NOS activity in soybean tissues proximal to the site of inoculation. The induced NOS activity was Ca(2+)- and NADPH-dependent and was sensitive to the NOS inhibitors N(G)-nitro-L-arginine methyl ester, aminoguanidine, and L-N(6)-(iminoethyl) lysine. NOS activity was not observed in SNP-elicited tissues. An antibody to brain NOS labeled a 166-kD protein in elicited and nonelicited cotyledons. Isoflavones (daidzein and genistein), pterocarpans (glyceollins), and flavones (apigenin and luteolin) were identified after exposure to the elicitor or SNP, although the accumulation of glyceollins and apigenin was limited in SNP-elicited compared with fungal-elicited cotyledons. NOS activity preceded the accumulation of these flavonoids in tissues treated with the Dpm elicitor. The accumulation of these metabolites was faster in SNP-elicited than in fungal-elicited cotyledons. We conclude that the response of soybean cotyledons to Dpm elicitor involves NO formation via a constitutive NOS-like enzyme that triggers the biosynthesis of antimicrobial flavonoids.
Subject: Dose-response Relationship, Drug
Enzyme Inhibitors
Flavonoids
Fungi
Guanidines
Homoarginine
Ng-nitroarginine Methyl Ester
Nitric Oxide Donors
Nitric Oxide Synthase
Nitroprusside
Plant Extracts
Seeds
Sesquiterpenes
Signal Transduction
Soybeans
Terpenes
Rights: fechado
Identifier DOI: 10.1104/pp.005850
Address: http://www.ncbi.nlm.nih.gov/pubmed/12427995
Date Issue: 2002
Appears in Collections:Unicamp - Artigos e Outros Documentos

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