Suchergebnisse

Fusarium avenaceum is a filamentous fungus infecting many plants and is one of the causal agents of the Fusarium Head Blight disease in wheat and barley. During plant infection, the fungus can produce secondary metabolites that are toxic for human and livestock (mycotoxins), among which the enniatins. Enniatins belong to the group of "emerging mycotoxins": first identified as early as 1950, the increasing occurrence of enniatins has only been documented over the last twenty years. Currently, enniatins are neither routinely analysed in grain harvests nor legislatively regulated, even though they are widespread and can be encountered in high concentrations. Diversity of enniatin-producing strains as well as the mechanisms by which their biosynthesis can be modulated during plant infection and/or in response to environmental conditions are poorly known. These gaps of knowledge hinder the development of tools for controlling and mitigating their presence in crops. In the present study, a comprehensive characterisation of the phenotypic diversity within the F. avenaceum species has been carried out. One of the studied phenotypic traits was the effect of pH variations on the fungal growth and toxin production, which has led to evidence various response profiles between strains. To go further, the role of FavPac1, the homologue of pacC/RIM101 encoding a transcriptional factor involved in the response to ambient pH in fungi, has been studied. Construction and phenotyping of deleted mutants, Fav∆Pac1, for four different F. avenaceum isolates have allowed suggesting an involvement of FavPac1 in the modulation of enniatin production and of the expression of biosynthetic genes induced by pH variations. Lastly, with the aim to identify alternatives to synthetic fungicides, the capacity of plant phenolic compounds to inhibit the yield of enniatins has been investigated. The antifungal and anti-mycotoxin properties of hydroxycinnamic acids have been shown; ferulic acid has been highlighted as the most potent compound. ...

International audience ; Enniatins (ENNs) that belong to the group of emerging mycotoxins are widespread contaminants of agricultural commodities. There is currently insufficient evidence to rule out health concerns associated with long-term exposure to ENNs and efforts must be strengthened to define a control strategy. While the potential of plant compounds to counteract the contamination with legislated mycotoxins has been reported, little remains known regarding ENNs. The present study evidenced for the first time the efficiency of hydroxycinnamic acids to inhibit the fungal growth and ENNs yield by Fusarium avenaceum. Notably, 0.5 mM of exogenous ferulic, caffeic, and p-coumaric acids led to a drastic reduction of ENNs synthesis in pH4 broths, with ferulic acid being the most potent. The ENNs production inhibitory activity of ferulic acid was shown to be associated with a significant down-regulation of the expression of ENNs biosynthetic genes. To further investigate the bioactivity of ferulic acid, its metabolic fate was characterized in fungal broths and the capacity of F. avenaceum to metabolize it through a C2-cleavage type degradation was demonstrated. Overall, our data support the promising use of ferulic acid in ENNs control strategies, either as part of an environmentally friendly plant-care product or as a biomarker of plant resistance.