Mycotoxins are a component of Fusarium graminearum stress-response system

Citation: Ponts N (2015) Mycotoxins are a component of Fusarium graminearum stress-response system. SECONDARY METABOLITES IN THE CONTEXT OF PHYTOPATHOGENIC FUNGAL LIFE Fusarium graminearum is a phytopathogenic Ascomycota that can cause Fusarium head blight in wheat and other cereals worldwide, leading to important yield losses as well as reduced grain quality. The analysis of the F. graminearum genome sequence revealed the presence of 20 non-ribosomal peptide synthases, 15 polyketide synthases, and 17 terpenoid synthases, all potentially involved in the production of a panel of secondary metabolites, including yet unknown ones, such as the mycotoxins deoxynivalenol (DON) and other type B trichothecenes (Cuomo et al., 2007). The toxicity of DON to humans and animals upon ingestion has been extensively illustrated (see Bonnet et al., 2012; Awad et al., 2013; Pinton and Oswald, 2014 for reviews), and the presence of this mycotoxin in cereal-derived food and feeds represents a serious threat for public health (reviewed in Marin et al., 2013; Sirot et al., 2013; Wu et al., 2014). Secondary metabolites are a structurally diverse family of compounds that are often qualified as unessential for short-term development but important for long-term survival (see Roze et al., 2011a for a review). Secondary metabolism is tightly linked to primary metabolism,starting with the fact that primary metabolites " feed " secondary metabolite biosynthetic pathways (reviewed in Audenaert et al., 2014; Sheridan et al., 2015). For example, the biosynthesis of type B trichothecenes by F. graminearum derives from the isoprenoid pathway, an essential metabolic pathway involved in various cellular processes. Remarkably, the genes involved in the biosynthesis of isoprenoids are positively regulated by the transcription factor Tri6, which also regulates the genes involved in the trichothecenes biosynthetic pathway (Seong et al., 2009). Moreover, Menke et al. (2013) proposed that type B trichothecenes are produced in specific cellular vesicles, so-called " toxisomes, " and found pieces of evidence that the HMG-CoA reductase of the isoprenoid pathway also localizes to toxisomes when the production of toxins is induced (Menke et al., 2013). Whether these toxisomes are neo-formed for toxin biosynthesis or derive from vesicles hosting elements of the primary metabolism remains to be investigated. Nonetheless, the production of mycotoxins by F. graminearum could be the result of a tight coordination with primary metabolism. Fungi are known to produce diverse families of secondary metabolites, biological functions of which are not yet fully understood. In the context of host-pathogen interactions, DON …