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Evidence of a Multicopper Oxidase in Mn Oxidation by Gaeumannomyces graminis var. tritici

Ian A Thompson, Don M Huber, Darrell G Schulze

    Phytopathology
    |October 24, 2008
    PubMed

    Insights

    The plant pathogen Gaeumannomyces graminis var. tritici uses a multicopper oxidase with laccase activity to oxidize manganese (Mn). This manganese oxidation factor (MOF) is an extracellular enzyme, potentially linking Mn oxidation to take-all disease virulence.

    Area of Science:

    • Plant Pathology
    • Mycology
    • Biochemistry

    Background:

    • Manganese (Mn) oxidation by Gaeumannomyces graminis var. tritici correlates with take-all disease virulence.
    • The specific mechanism of Mn oxidation in this fungus remains inadequately understood.
    • Multicopper oxidases are known to mediate Mn oxidation in other microorganisms.

    Purpose of the Study:

    • To investigate the mechanism of Mn oxidation by Gaeumannomyces graminis var. tritici.
    • To characterize the manganese oxidizing factor (MOF) produced by the fungus.
    • To determine if the MOF is a multicopper oxidase.

    Main Methods:

    • Cultural characterization of the MOF.
    • Spectrophotometric analysis of the MOF.
    • Cellulose acetate electrophoresis to analyze the MOF.
    • Estimation of the MOF's molecular weight.

    Main Results:

    • The MOF is an extracellular enzyme.
    • The estimated molecular weight of the MOF is between 50 and 100 kDa.
    • Electrophoresis and spectrophotometry revealed the MOF is a multicopper oxidase with laccase activity.

    Conclusions:

    • Gaeumannomyces graminis var. tritici oxidizes manganese via an extracellular multicopper oxidase with laccase activity.
    • The characterized MOF is likely responsible for Mn oxidation in this plant pathogen.
    • This finding provides insight into the biochemical mechanisms potentially underlying take-all disease virulence.

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