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Effects of xanthotoxin treatment on trichothecene production in Fusarium sporotrichioides

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Abstract:

There are 4 P450 oxygenases involved in the biosynthesis of T-2 toxin in Fusarium sporotrichioides. Exactly how these enzymes react to antimicrobial plant defense compounds is unknown. Xanthotoxin (8-methoxypsoralen) is a phototoxic furanocoumarin that acts as a P450 oxygenase inhibitor. The current study shows that the addition of concentrations of 1.0 mmol/L or less of xanthotoxin to liquid cultures of F. sporotrichioides NRRL3299 can effectively block T-2 toxin production and cause an increase in accumulation of trichodiene, the hydrocarbon precursor of trichothecenes. The addition of xanthotoxin to liquid cultures of a trichodiene-accumulating F. sporotrichioides Tri4- mutant caused a 3- to 10-fold increase in trichodiene accumulation, suggesting that xanthotoxin not only blocks trichothecene oxygenation reactions, but may in some way also promote the synthesis of trichodiene. Feeding studies showed that 2 of the 4 P450 oxygenases, TRI4 and TRI1, were more sensitive to xanthotoxin, while oxygenases TRI11 and TRI13 were unaffected. Quantitative reverse-transcriptase PCR indicated that several of the genes in the toxin biosynthetic pathway were upregulated by xanthotoxin, with Tri4 showing the highest increase in expression. These results indicate that while xanthotoxin inhibits specific P450 oxygenase activity, it also has an effect on gene expression.

Il existe quatre oxygénases P450 impliquées dans la biosynthèse de la toxine T-2 de Fusarium sporotrichoides. On ne sait pas exactement comment ces enzymes réagissent aux composés associés à la défense antimicrobienne des plantes. La xanthotoxine (8-méthylpsoralène) est un furanocoumarin phototoxique qui agit comme inhibiteur des oxygénases P450. L’étude présente a démontré que l’ajout de 1.0 mM ou moins de xanthotoxine à des cultures liquides de F. sporotrichoides NRRL3299 pouvait effectivement bloquer la production de la toxine T-2 et causer une augmentation de l’accumulation de trichodiène, l’hydrate de carbone précurseur des trichothécènes. L’ajout de xanthotoxine à des cultures liquides du mutant F. sporotrichoides Tri4- qui accumule le trichodiène a causé une augmentation de 3 à 10 fois de l’accumulation du trichodiène, ce qui suggère que la xanthotoxine ne bloque pas seulement les réactions d’oxygénation du trichothécène, mais favorise d’une quelconque façon la synthèse de trichodiène. Des études d’alimentation ont démontré que 2 des 4 oxygénases, TRI4 et TRI1, étaient plus sensibles à la xanthotoxine alors que les oxygénases TRI11 et TRI13 n’étaient pas affectées. Des analyses en PCR réverse quantitative (qRT-PCR) ont indiqué que plusieurs des gènes de la voie de biosynthèse de la toxine étaient réglés positivement par la xanthotoxine, l’expression de Tri4 étant la plus augmentée. Ces résultats indiquent qu’alors que la xanthotoxine inhibe l’activité d’oxygénases spécifiques, elle exerce aussi un effet sur l’expression génique.

Document Type: Research Article

Publication date: 2008-12-01

More about this publication?
  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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