Trichothecenes are sesquiterpenoid toxins produced by diverse ascomycetes, including
Fusarium. The trichothecene analog deoxynivalenol (DON) produced by the Fusarium head blight (FHB) pathogen
Fusarium graminearum is a virulence factor on wheat and a major food and feed safety concern. In
Fusarium,
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Trichothecenes are sesquiterpenoid toxins produced by diverse ascomycetes, including
Fusarium. The trichothecene analog deoxynivalenol (DON) produced by the Fusarium head blight (FHB) pathogen
Fusarium graminearum is a virulence factor on wheat and a major food and feed safety concern. In
Fusarium, the trichothecene biosynthetic gene (
TRI) cluster consists of 7–14 genes. Most
TRI cluster genes are conserved and their specific roles in trichothecene biosynthesis have been determined. An exception is
TRI14, which is not required for DON synthesis in vitro but is required for spread of
F. graminearum in wheat heads. In the current study, gene expression analyses revealed that TRI14 was highly induced in infected wheat heads. We demonstrated that TRI14 was not only required for
F. graminearum spread but also important for initial infection in wheat. Although a prior study did not detect DON in infected seeds, our analyses showed significantly less DON and fungal biomass in
TRI14-mutant (designated ∆
tri14)-inoculated heads than wild-type-inoculated heads. Gene expression comparison showed that the level of expression of
TRI genes was similar in the wheat tissues infected with ∆
tri14 or the wild type, indicating the reduced toxin levels caused by ∆
tri14 may be due to less fungal growth. ∆
tri14 also caused less lesion and grew less in wheat coleoptiles than the wild type. The growth of ∆
tri14 in carboxymethylcellulose medium was more sensitive to hydrogen peroxide than the wild type. The data suggest that
TRI14 plays a critical role in
F. graminearum growth, and potentially protects the fungus from plant defense compounds.
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