Multiplication du Virus de la Mosaïque du Tabac dans des Hôtes à Réponse Systémique ou Nécrotique: Approche Biochimique à l'Étude de la Résistance Hypersensible aux Virus

Konaté, G.; Kopp, M.; Fritig, Bernard

doi:10.1111/j.1439-0434.1982.tb00680.x

Cited by 12 publications

(5 citation statements)

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“…Virus can be found only in the necrotic lesions and in a small layer of cells surrounding these lesions. This mechanism of virus localization in hypersensitive hosts is responsible for a decrease in final virus yield by several orders of magnitude as compared to that in systematically infected hosts (21,28). Once local lesions start to develop, changes in enzyme activities and in proteins become apparent (25,39,41,44).…”

Section: Introductionmentioning

confidence: 99%

Purification and characterization of 8 of the pathogenesis-related proteins in tobacco leaves reacting hypersensitively to tobacco mosaic virus

Jamet

Fritig

1986

Plant Mol Biol

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Leaves of tobacco plants (Nicotiana tabacum cv. Samsun NN) which are reacting hypersensitively to infection with tobacco mosaic virus contain 10 major pathogenesis-related (PR) proteins which are absent, or present in small amounts in uninfected leaves. We describe here a preparative procedure of purification of the tobacco PR-proteins which involves a combination of conventional and high-performance liquid chromatography. The separation and isolation of the proteins were based on differences in net charge at different pH values, in isoelectric point and in apparent molecular weight. This procedure led to the purification to homogeneity of 8 PR-proteins, as shown by polyacrylamide slab gel electrophoresis (PAGE) of the purified proteins under denaturing and non-denaturing conditions. These were the 3 well-known proteins PR-1a,-1b and-1c, and 5 other major PR-proteins, called PR-2,-N,-O,-P and-Q, according to the nomenclature of Van Loon (39). None of the purified PR-proteins gave a positive Schiff reaction for carbohydrate content. Molecular weight determinations from gel permeation chromatography and from sodium dodecyl sulphate (SDS)-PAGE indicated that all 8 PR-proteins were monomers and that three groups could be distinguished among them. The first group is the PR-1 group containing PR-1a,-1b and-1c (12000 MW), the second consists of PR-P and PR-Q (14000 MW) and the third of PR-2, PR-N and PR-O (25000 MW). In the PR-1 group, PR-1a can be distinguished clearly from the two other members on denaturing slab gels containing both SDS and urea.

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Section: Introductionmentioning

confidence: 99%

Purification and characterization of 8 of the pathogenesis-related proteins in tobacco leaves reacting hypersensitively to tobacco mosaic virus

Jamet

Fritig

1986

Plant Mol Biol

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“…This induction of defense responses in the sharp zone surrounding the HR cells might be essential to restrict pathogen spread. It is known for example that in Tobacco Mosaic Virus-induced HR, the cells immediately beyond the necrotic region contain virus particles (Konate et al, 1982). It was suggested that cells undergoing HR might release signals regulating defense responses in the tissue next to the infection site (Kombrick and Somssich, 1995).…”

Section: Is There a Social Role For The Hr?mentioning

confidence: 99%

The hypersensitive response and the induction of cell death in plants

1997

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The hypersensitive response, or HR, is a form of cell death often associated with plant resistance to pathogen infection. Reactive oxygen intermediates and ion fluxes are proximal responses probably required for the HR. Apoptosis as defined in animal systems is, thus far, not a strict paradigm for the HR. The diversity observed in plant cell death morphologies suggests that there may be multiple pathways through which the HR can be triggered. Signals from pathogens appear to interfere with these pathways. HR may play in plants the same role as certain programmed cell deaths in animals with respect to restricting pathogen growth. In addition, the HR could regulate the defense responses of the plant in both local and distant tissues.

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“…In tobacco reacting hypersensitively to TMV, the cells beyond necrotic lesions still contain infectious virus particles (Konate et al, 1982). This observation shows that hypersensitive cell death is not sufficient to restrict pathogen spread and that defense responses induced in living cells that surround HR cells are required for full pathogen containment.…”

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confidence: 99%

Downregulation of a Pathogen-Responsive Tobacco UDP-Glc:Phenylpropanoid Glucosyltransferase Reduces Scopoletin Glucoside Accumulation, Enhances Oxidative Stress, and Weakens Virus Resistance

et al. 2002

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Plant UDP-Glc:phenylpropanoid glucosyltransferases (UGTs) catalyze the transfer of Glc from UDP-Glc to numerous substrates and regulate the activity of compounds that play important roles in plant defense against pathogens. We previously characterized two tobacco salicylic acid-and pathogen-inducible UGTs (TOGTs) that act very efficiently on the hydroxycoumarin scopoletin and on hydroxycinnamic acids. To identify the physiological roles of these UGTs in plant defense, we generated TOGT-depleted tobacco plants by antisense expression. After inoculation with Tobacco mosaic virus (TMV), TOGT-inhibited plants exhibited a significant decrease in the glucoside form of scopoletin (scopolin) and a decrease in scopoletin UGT activity. Unexpectedly, free scopoletin levels also were reduced in TOGT antisense lines. Scopolin and scopoletin reduction in TOGT-depleted lines resulted in a strong decrease of the blue fluorescence in cells surrounding TMV lesions and was associated with weakened resistance to infection with TMV. Consistent with the proposed role of scopoletin as a reactive oxygen intermediate (ROI) scavenger, TMV also triggered a more sustained ROI accumulation in TOGT-downregulated lines. Our results demonstrate the involvement of TOGT in scopoletin glucosylation in planta and provide evidence of the crucial role of a UGT in plant defense responses. We propose that TOGT-mediated glucosylation is required for scopoletin accumulation in cells surrounding TMV lesions, where this compound could both exert a direct antiviral effect and participate in ROI buffering. INTRODUCTIONPlants are characterized by their ability to synthesize numerous different secondary metabolites, among them phenylpropanoids, which are derived from Phe and fulfill a wide range of important biological functions (Dixon and Paiva, 1995). It is well established that phenylpropanoid metabolism is one of the major metabolic pathways stimulated during the hypersensitive response (HR), a very efficient mechanism of induced disease resistance in plants. The HR is characterized by localized cell and tissue death at the site of infection and is associated with the induction of intense metabolic alterations, resulting in confinement of the pathogen (Hammond-Kosack and Jones, 1996;Fritig et al., 1998). One of the earliest responses underlying HR cell death in plants is the increase in the production of reactive oxygen intermediates (ROIs), giving rise to the so-called oxidative burst (Hammond-Kosack and Jones, 1996).Among the ROIs, O 2 . Ϫ and H 2 O 2 may be key mediators of cell death characterizing the HR . On the other hand, H 2 O 2 from the oxidative burst also could act as a diffusible signal for the induction of protectant genes in cells adjacent to HR lesions, thereby limiting oxidant-mediated cell death (Lamb and Dixon, 1997). The cells surrounding the HR lesion actually are stimulated strongly without being destined to die, and they produce a large set of defense responses that contribute to the efficient restriction of pathogen spread (Dorey e...

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Multiplication du Virus de la Mosaïque du Tabac dans des Hôtes à Réponse Systémique ou Nécrotique: Approche Biochimique à l'Étude de la Résistance Hypersensible aux Virus

Cited by 12 publications

References 11 publications

Purification and characterization of 8 of the pathogenesis-related proteins in tobacco leaves reacting hypersensitively to tobacco mosaic virus

Purification and characterization of 8 of the pathogenesis-related proteins in tobacco leaves reacting hypersensitively to tobacco mosaic virus

The hypersensitive response and the induction of cell death in plants

Downregulation of a Pathogen-Responsive Tobacco UDP-Glc:Phenylpropanoid Glucosyltransferase Reduces Scopoletin Glucoside Accumulation, Enhances Oxidative Stress, and Weakens Virus Resistance

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