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Patrick Saindrenan - One of the best experts on this subject based on the ideXlab platform.

  • over expression of a Scopoletin glucosyltransferase in nicotiana tabacum leads to precocious lesion formation during the hypersensitive response to tobacco mosaic virus but does not affect virus resistance
    Plant Molecular Biology, 2004
    Co-Authors: Rachel Baltz, Patrick Saindrenan, Claire M M Gachon
    Abstract:

    Nicotiana tabacum Togt encodes a Scopoletin glucosyltransferase (UDPglucose:Scopoletin O-β-D-glucosyltransferase, EC 2.4.1.128) known to act in vitro on many different substrates including the 6-methoxy-7-hydroxy- coumarin Scopoletin. This phenolic compound accumulates in vast amounts, essentially in its glucosylated form scopolin, in tobacco during the hypersensitive response (HR) to tobacco mosaic virus (TMV). To identify the physiological role of this pathogen-inducible UDP-Glc glucosyltransferase (UGT), we generated TOGT over-expressing transgenic plants. Although no endogenous Scopoletin or scopolin could be detected before infection, the accumulation of both the aglycone and the glucoside was found to be 2-fold higher in transgenic plants after inoculation with TMV than in wild-type plants. Scopoletin UGT activity in plants over-expressing Togt was significantly higher during the HR than in control plants. This up-regulated activity was associated with a strong increase of the bright blue fluorescence surrounding the HR-necrotic lesions under UV light, which is known to correlate with Scopoletin and scopolin abundance. Necrosis appeared sooner in transgenic plants and lesions developed faster, suggesting an accelerated HR. Unexpectedly, the viral content in each lesion was not significantly different in transgenic and in wild-type plants. These results are discussed in relation to the role of TOGT as the major UDP-Glc: Scopoletin glucosyltransferase and to the importance of Scopoletin accumulation during the HR.

  • downregulation of a pathogen responsive tobacco udp glc phenylpropanoid glucosyltransferase reduces Scopoletin glucoside accumulation enhances oxidative stress and weakens virus resistance
    The Plant Cell, 2002
    Co-Authors: Julie Chong, Rachel Baltz, Corinne Schmitt, Roland Beffa, Bernard Fritig, Patrick Saindrenan
    Abstract:

    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.

Rachel Baltz - One of the best experts on this subject based on the ideXlab platform.

  • over expression of a Scopoletin glucosyltransferase in nicotiana tabacum leads to precocious lesion formation during the hypersensitive response to tobacco mosaic virus but does not affect virus resistance
    Plant Molecular Biology, 2004
    Co-Authors: Rachel Baltz, Patrick Saindrenan, Claire M M Gachon
    Abstract:

    Nicotiana tabacum Togt encodes a Scopoletin glucosyltransferase (UDPglucose:Scopoletin O-β-D-glucosyltransferase, EC 2.4.1.128) known to act in vitro on many different substrates including the 6-methoxy-7-hydroxy- coumarin Scopoletin. This phenolic compound accumulates in vast amounts, essentially in its glucosylated form scopolin, in tobacco during the hypersensitive response (HR) to tobacco mosaic virus (TMV). To identify the physiological role of this pathogen-inducible UDP-Glc glucosyltransferase (UGT), we generated TOGT over-expressing transgenic plants. Although no endogenous Scopoletin or scopolin could be detected before infection, the accumulation of both the aglycone and the glucoside was found to be 2-fold higher in transgenic plants after inoculation with TMV than in wild-type plants. Scopoletin UGT activity in plants over-expressing Togt was significantly higher during the HR than in control plants. This up-regulated activity was associated with a strong increase of the bright blue fluorescence surrounding the HR-necrotic lesions under UV light, which is known to correlate with Scopoletin and scopolin abundance. Necrosis appeared sooner in transgenic plants and lesions developed faster, suggesting an accelerated HR. Unexpectedly, the viral content in each lesion was not significantly different in transgenic and in wild-type plants. These results are discussed in relation to the role of TOGT as the major UDP-Glc: Scopoletin glucosyltransferase and to the importance of Scopoletin accumulation during the HR.

  • downregulation of a pathogen responsive tobacco udp glc phenylpropanoid glucosyltransferase reduces Scopoletin glucoside accumulation enhances oxidative stress and weakens virus resistance
    The Plant Cell, 2002
    Co-Authors: Julie Chong, Rachel Baltz, Corinne Schmitt, Roland Beffa, Bernard Fritig, Patrick Saindrenan
    Abstract:

    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.

Claire M M Gachon - One of the best experts on this subject based on the ideXlab platform.

  • over expression of a Scopoletin glucosyltransferase in nicotiana tabacum leads to precocious lesion formation during the hypersensitive response to tobacco mosaic virus but does not affect virus resistance
    Plant Molecular Biology, 2004
    Co-Authors: Rachel Baltz, Patrick Saindrenan, Claire M M Gachon
    Abstract:

    Nicotiana tabacum Togt encodes a Scopoletin glucosyltransferase (UDPglucose:Scopoletin O-β-D-glucosyltransferase, EC 2.4.1.128) known to act in vitro on many different substrates including the 6-methoxy-7-hydroxy- coumarin Scopoletin. This phenolic compound accumulates in vast amounts, essentially in its glucosylated form scopolin, in tobacco during the hypersensitive response (HR) to tobacco mosaic virus (TMV). To identify the physiological role of this pathogen-inducible UDP-Glc glucosyltransferase (UGT), we generated TOGT over-expressing transgenic plants. Although no endogenous Scopoletin or scopolin could be detected before infection, the accumulation of both the aglycone and the glucoside was found to be 2-fold higher in transgenic plants after inoculation with TMV than in wild-type plants. Scopoletin UGT activity in plants over-expressing Togt was significantly higher during the HR than in control plants. This up-regulated activity was associated with a strong increase of the bright blue fluorescence surrounding the HR-necrotic lesions under UV light, which is known to correlate with Scopoletin and scopolin abundance. Necrosis appeared sooner in transgenic plants and lesions developed faster, suggesting an accelerated HR. Unexpectedly, the viral content in each lesion was not significantly different in transgenic and in wild-type plants. These results are discussed in relation to the role of TOGT as the major UDP-Glc: Scopoletin glucosyltransferase and to the importance of Scopoletin accumulation during the HR.

Serge Kauffmann - One of the best experts on this subject based on the ideXlab platform.

  • Scopoletin expression in elicitor treated and tobacco mosaic virus infected tobacco plants
    Physiologia Plantarum, 2002
    Co-Authors: Laurent Costet, Bernard Fritig, Serge Kauffmann
    Abstract:

    Localized acquired resistance (LAR) characterizes a narrow zone of living cells expressing strong defense responses and surrounding cells undergoing a hypersensitive response (HR). In Samsun NN tobacco plants, tissues undergoing tobacco mosaic virus-induced or elicitor-induced LAR exhibit a strong blue fluorescence under UV light. We have shown that Scopoletin and its glucoside, scopolin, accounted for the fluorescence: (1) both compounds were identified after extraction and purification by thin layer and high performance liquid chromatography; (2) there was a strict correlation between the occurrence of fluorescence and accumulation of high amounts of Scopoletin; and (3) infiltration of commercial Scopoletin caused a similar fluorescence to that occurring in LAR tissues. There was a 20-fold increase in Scopoletin levels in LAR tissues compared to tissues treated with a non-HR dose of elicitor, while PR1 protein accumulated in similar amounts in both types of tissues. Scopoletin was able to suppress the elicitor-induced HR only when co-infiltrated with very low HR-dose of elicitor. These two observations suggested that, although Scopoletin alone would not be able to control the development of the HR through its known antioxidant activity, it may nevertheless participate to such function of LAR tissues in combination with other antioxidant molecules.

Jesus Jorrin - One of the best experts on this subject based on the ideXlab platform.

  • characterization and inducibility of a Scopoletin degrading enzyme from sunflower
    Phytochemistry, 1997
    Co-Authors: Robert Edwards, Stephen M Stones, Maricarmen Gutierrezmellado, Jesus Jorrin
    Abstract:

    Abstract The role of an enzyme, tentatively identified as a peroxidase, in the metabolism of the coumarin phytoalexin Scopoletin has been investigated in sunflower. When sunflower leaf discs were fed with 0.05 mM Scopoletin the coumarin was initially slowly metabolized by glycosylation. After a delay of 24 hr Scopoletin then rapidly disappeared and this could not be accounted for by the accumulation of extractable metabolises. Instead, the disappearance of Scopoletin was associated with the increased activity of peroxidase which metabolized the coumarin to a coloured insoluble metabolise. The Scopoletin-peroxidase was purified 222-fold and had a M r of 46 000 and was associated with peroxidase activity toward esculetin and guaiacol, but not ayapin. In leaves, the activity of the Scopoletin-peroxidase was increased locally around wound sites and its activity could be elevated at more distant sites by treatment with CuCl 2 or salicylic acid. The Scopoletin-peroxidase activity was also identified in peas, tobacco and potato. © 1997 Elsevier Science Ltd. All rights reserved