An Acidic pH is a determinant factor for TRI genes expression and trichothecenes B biosynthesis in Fusarium graminearum

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Merhej, Jawad | Boutigny, Anne-Laure | Pinson-Gadais, Laetitia | Richard-Forget, Florence | Barreau, Christian

Edité par CCSD -

International audience. Reducing production of trichothecene B by Fusarium graminearum on cereals is necessary to avoid contamination leading to yields reduction and having harmful impacts on human and animal health. Understanding how trichothecenes biosynthesis is induced is essential. Effect of ambient pH on fungal growth, toxin biosynthesis and TRI genes expression was studied during in vitro liquid culture of F. graminearum on minimal medium. Fungal development stopped at day 3 after a sharp pH drop in the medium. At the same time, induction of TRI genes expression was observed and toxin started to accumulate one day later. Acidification seems a determinant factor for induction, as neither the toxin nor the TRI genes were detected when the pH is maintained neutral. Shifting from neutral to acidic pH by mycelium transfer induced TRI genes expression and toxin accumulation. The regulation of toxin production by the ambient pH seemed to be specific to some TRI genes since TRI5, located in the core FgTRI5 cluster, showed an immediate induction while TRI101, located elsewhere in the genome, showed a more progressive response. The regulation of trichothecenes biosynthesis by the ambient pH seems to be a general mechanism, independent from strains or chemotype as all tested strains, including F. graminearum and F. culmorum species, showed a regulation of toxin production in response to the ambient pH. We conclude that in vitro, external acidification is required for induction of TRI genes expression.

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