Abstract
Plant-derived compounds limiting mycotoxin contamination are currently of major interest in food and feed production. However, their potential application requires an evaluation of their effects on fungal secondary metabolism and membrane effects. In this study, different strains of Fusarium culmorum and F. graminearum sensu stricto were exposed to trans-cinnamic and chlorogenic acids on solid YES media. Fusaria produced phenolic acids, whose accumulation was lowered by exogenous phenolic compounds. In addition, fungi reduced exogenous phenolic acids, leading either to their conversion or degradation. trans-Cinnamic acid was converted to caffeic and ferulic acids, while chlorogenic acid was degraded to caffeic acid. The latter underwent further degradation to protocatechuic acid. Fungal-derived trans-cinnamic acid, as the first intermediate of the shikimate pathway, increased after chlorogenic acid treatment, presumably due to the further inhibition of the conversion of trans-cinnamic acid. Exogenous trans-cinnamic and chlorogenic acid displayed the inhibition of mycotoxin production by Fusaria, which appeared to be largely dependent on the phenolic compound and its concentration and the assayed strain. Exogenous phenolic acids showed different effects on ergosterol biosynthesis by fungi. It was found that the production of this membrane sterol was stimulated by trans-cinnamic acid, while chlorogenic acid negatively impacted ergosterol biosynthesis, suggesting that phenolic acids with stronger antifungal activities may upregulate ergosterol biosynthesis by Fusaria. This paper reports on the production of phenolic acids by Fusaria for the first time.
Highlights
Fusarium head blight (FHB) of small grain cereals and Fusarium Ear Rot (FER) of maize remain among the most important diseases affecting cereals worldwide
Among the cinnamic-derived acids, ferulic acid was quantified at the highest levels, comprising nearly 21.5–24% of the phenolic acids. p-Coumaric acid, which in plants gets converted into ferulic acid by the hydroxylation and methylation reaction [43,44], was quantified at slightly lower levels than ferulic acid, comprising 19–22.5% of the phenolic acids
Changes in ergosterol biosynthesis might be explained by the different antifungal activities of phenolic acids. trans-Cinnamic acid exhibits remarkably stronger antifungal activity than chlorogenic acid, which, as demonstrated by Ponts et al [22], can be attributed to the differences in their lipophilicity, scored using retention times (Table 2)
Summary
Fusarium head blight (FHB) of small grain cereals and Fusarium Ear Rot (FER) of maize remain among the most important diseases affecting cereals worldwide. Among the predominating fungi causing both diseases are Fusarium graminearum sensu stricto (s.s.) and F. culmorum [1,2]. Besides yield losses, they cause quality decline by contamination of the grain with type B trichothecenes. They cause quality decline by contamination of the grain with type B trichothecenes Fungicide treatment offers the best protection of crops against fungal pathogens, including Fusaria [5]. Chemical control may not be fully effective in reducing mycotoxin contamination [6], which underlines the continuous need for the development of novel fungicides
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