Menadione-induced oxidative stress re-shapes the oxylipin profile of Aspergillus flavus and its lifestyle

Aspergillus flavus is an efficient producer of mycotoxins, particularly aflatoxin B1, probably the most hepatocarcinogenic naturally-occurring compound. Although the inducing agents of toxin synthesis are not unanimously identified, there is evidence that oxidative stress is one of the main actors in play. In our study, we use menadione, a quinone extensively implemented in studies on ROS response in animal cells, for causing stress to A. flavus. For uncovering the molecular determinants that drive A. flavus in challenging oxidative stress conditions, we have evaluated a wide spectrum of several different parameters, ranging from metabolic (ROS and oxylipin profile) to transcriptional analysis (RNA-seq). There emerges a scenario in which A. flavus activates several metabolic processes under oxidative stress conditions for limiting the ROS-associated detrimental effects, as well as for triggering adaptive and escape strategies

Environmental stresses affect aflatoxin synthesis and conidiogenesis in a. flavus through sirtuin pathway involvement.

Aflatoxins are health hazardous secondary metabolites produced by the cosmopolitan fungus A. flavus. The ability of this fungus to exploit several substrates is also related to its psicrophylicity and enormous production of conidia. In relation to this, some ongoing climate changes favor plant susceptibility to the attack by this fungus with a consequent, dangerous, increase of aflatoxins into previously unexploited feed- and foodstuff. In this study we analyze how some environmental stresses to which A. flavus may undergo also during host exploitation – namely, hypoxia, pH alteration, carbon starvation and oxidative stress – affect aflatoxin biosynthesis, fungal growth and conidiogenesis. By multiple analytical approaches (mass spectrometry, transcriptional analysis, fluorimetric assays) we check the trend of specific molecular pathways related to metabolism reprogramming in consequence of environmental signals. Results indicate that sirtuins– a class of deacetylase enzymes – could represent the interface between signal transduction pathways and transcriptional reprogramming into A. flavus.Nevertheless the results obtained, further study to clearly define the role of sirtuins in shaping transcriptome in A. flavus are required

Control of mycotoxins in feeds by novel more environmental friendly strategies

Mycotoxins, secondary metabolites produced by some filamentous fungi during their growth on food and feed commodities, represent a serious health hazard due to their possible cytotoxic and genotoxic effects for human and animals. The presence of some mycotoxins in foods and feeds can induce tumours, immune suppression and lowering of animal production. The levels of different mycotoxins, like aflatoxins, ochratoxin A and fusarium toxins in food and feed commodities are limited by law. Up to day the control of the mycotoxins in foods and feeds is mainly achieved by the use of chemical compounds. This strategy could arise environmental problems and select fungal strains resistant to their effects. Some natural compounds like mushroom β-glucans and plant derived antioxidants have demonstrated the ability to provide a long lasting control of the biosynthesis of different mycotoxins, both in vitro and on stored maize and wheat seeds. Furthermore, mushroom' β-glucans have proven a significant immune-enhancing effects on human and animal cells. Thus, their use in a challenge against mycotoxins could provide not only the control of these secondary metabolites but also an improvement of animal well-being

INIBIZIONE della BIOSINTESI di differenti MICOTOSSINE nei cereali tramite composti bioattivi estratti dal basidiomicete Trametes versicolor

Le micotossine sono metaboliti secondari dannosi per la salute dell’uomo e degli animali prodotti da numerose e ampiamente diffuse specie fungine che possono contaminare diverse derrate alimentari. Le aflatossine, l’ocratossina A e i tricoteceni sono le micotossine più presenti sia durante le fasi di campo che in quelle del post-raccolta e, nei Paesi a clima mediterraneo, sono principalmente prodotte da specie fungine appartenenti rispettivamente ai generi Aspergillus e Fusarium. Nel nostro lavoro abbiamo utilizzato degli eso-polisaccaridi ed enzimi ligninolitici estratti dal basidiomicete Trametes versicolor, capaci di controllare la produzione e degradare significativamente le aflatossine, ocratossina A e deossinivalenolo su semi di grano duro, tenero e mais. I composti utilizzati non sono tossici per l’uomo e per gli animali e possono quindi costituire uno strumento innovativo per garantire la qualità delle derrate alimentari e degli alimenti.Mycotoxins are harmful secondary metabolites produced by several widespread environment contaminating fungi mainly belonging to Fusarium, Aspergillus and Penicillium genera. In our diet we experience a harmful daily consumption of mycotoxin-contaminated foods. Recently, many natural-based antioxidant or biocontrol-related strategies have been assessed as environmentfriendly approaches for controlling the production of many mycotoxins in feed and foodstuffs. Here we show that raw, semi-purified and purified exo-polysaccharides and some secreted hydrolytic enzymes (e.g. ligninolytic enzymes) from these mushrooms have demonstrated the ability both to inhibit the biosynthesis or (and) to degrade aflatoxins, ochratoxin A, Fusarium toxins already present in wheat and maize seeds. The results obtained are promising in view to apply a more environmental friendly strategy to achieve an improved control of different toxins at once