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United States Department of Agriculture

Agricultural Research Service

Title: Fdb1 and Fdb2, Fusarium Verticillioides Loci Necessary for Detoxification of Preformed Antimicrobials from Corn

Authors
item Glenn, Anthony
item Gold, S - PLANT PATHOL/UGA, ATHENS
item Bacon, Charles

Submitted to: Molecular Plant Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 12, 2001
Publication Date: February 1, 2002

Interpretive Summary: Fusarium verticillioides (=Fusarium moniliforme) is a fungus of significant economic importance because of its deleterious effects on plant and animal health and the quality of their products. Corn (=Zea mays) is the primary host for F. verticillioides, yet corn does have a natural defensive mechanism involving production of compounds that are toxic to microbes such as fungi. We have investigated the impact of the plant's antimicrobial compounds (DIMBOA, DIBOA, MBOA, and BOA) on the ability of the fungus to infect, colonize, and cause disease on corn seedlings. We report genetic analyses indicating that two loci, Fdb1 and Fdb2, are involved in detoxification by the fungus. Mutation at either locus resulted in F. verticillioides being sensitive to the corn antimicrobials since it lacks the ability to detoxify them. Further details are presented regarding the detoxification pathway, including evidence suggesting production of an unknown intermediate compound. Based on genetic and physiological data, a branched detoxification pathway is proposed. Use of genetically characterized detoxifying and non-detoxifying strains indicated detoxification of the corn antimicrobials was not necessary for development of seedling blight or for infection and endophytic colonization of seedlings since the sensitive mutants could still infect, colonize, and cause disease. Thus, production of the antimicrobials by corn does not appear to be an effective resistance mechanism against F. verticillioides.

Technical Abstract: Fusarium verticillioides (=Fusarium moniliforme) is a fungus of significant economic importance because of its deleterious effects on plant and animal health and the quality of their products. Corn (=Zea mays) is the primary host for F. verticillioides, and we have investigated the impact of the plant's antimicrobial compounds (DIMBOA, DIBOA, MBOA, and BOA) on fungal virulence and systemic colonization. F. verticillioides is able to metabolize these antimicrobials, and genetic analyses indicated two loci, Fdb1 and Fdb2, were involved in detoxification. Mutation at either locus caused sensitivity and no detoxification. In vitro physiological complementation assays resulted in detoxification of BOA and suggested an unknown intermediate compound was produced. Production of the intermediate involved Fdb1, and a lesion in Fdb2 preventing complete metabolism of BOA resulted in transformation of the intermediate into an unidentified metabolite. Based on genetic and physiological data, a branched detoxification pathway is proposed. Use of genetically characterized detoxifying and non- detoxifying strains indicated detoxification of the corn antimicrobials was not a virulence factor since detoxification was not necessary for development of seedling blight or for infection and endophytic colonization of seedlings. Production of the antimicrobials does not appear to be an effective resistance mechanism against F. verticillioides.

Last Modified: 7/31/2014
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