How Peroxisomes Affect Aflatoxin Biosynthesis in Aspergillus Flavus

Abstract

In filamentous fungi, peroxisomes are crucial for the primary metabolism and play a pivotal role in the formation of some secondary metabolites. Further, peroxisomes are important site for fatty acids β-oxidation, the formation of reactive oxygen species and for their scavenging through a complex of antioxidant activities. Oxidative stress is involved in different metabolic events in all organisms and it occurs during oxidative processes within the cell, including peroxisomal β-oxidation of fatty acids. In Aspergillus flavus, an unbalance towards an hyper-oxidant status into the cell is a prerequisite for the onset of aflatoxin biosynthesis. In our preliminary results, the use of bezafibrate, inducer of both peroxisomal β-oxidation and peroxisome proliferation in mammals, significantly enhanced the expression of pex11 and foxA and stimulated aflatoxin synthesis in A. flavus. This suggests the existence of a correlation among peroxisome proliferation, fatty acids β-oxidation and aflatoxin biosynthesis. To investigate this correlation, A. flavus was transformed with a vector containing P33, a gene from Cymbidium ringspot virus able to induce peroxisome proliferation, under the control of the promoter of the Cu,Zn-sod gene of A. flavus. This transcriptional control closely relates the onset of the antioxidant response to ROS increase, with the proliferation of peroxisomes in A. flavus. The AfP33 transformant strain show an up-regulation of lipid metabolism and an higher content of both intracellular ROS and some oxylipins. The combined presence of a higher amount of substrates (fatty acids-derived), an hyper-oxidant cell environment and of hormone-like signals (oxylipins) enhances the synthesis of aflatoxins in the AfP33 strain. The results obtained demonstrated a close link between peroxisome metabolism and aflatoxin synthesis.

Antifungal and antiaflatoxigenic activities of coumarinyl thiosemicarbazides against Aspergillus flavus NRRL 3251

“…It is well established that increased oxidative stress within fungal cells triggers aflatoxin synthesis (20)(21)(22). Thus, a decrease in fungal cell oxidative stress caused by exogenously added antioxidants might be one of the possible reasons for decreased aflatoxin production.…”

Further characterization of the role of the mitochondrial high-mobility group box protein in the intracellular redox environment of Aspergillus nidulans

“…An intriguing relation between oxidative stress, secondary metabolite production and sexual development has been unfolding during the last few years in Aspergillus, which was initiated by the work of Reverberi et al (2007) on Aspergillus parasiticus and Aspergillus ochraceus, and further studied by many others (Baidya et al, 2014;Grintzalis et al, 2014;Reverberi et al, 2012;Wartenberg et al, 2012;Yin et al, 2013). In A. nidulans, the stress response proteins NapA and DlpA have been shown to play a role in developmental processes and sterigmatocystin production (Wartenberg et al, 2012;Yin et al, 2013).…”

Functional roles of the fatty acid desaturases encoded by KlOLE1, FAD2 and FAD3 in the yeast Kluyveromyces lactis

“…The resulting fatty acid methyl esters (FAMEs) were analysed with a gas chromatograph (GC-HP5890 series II) equipped with flame ionization detector (FID) using a capillary column SPB PUFA 30 m 0.25 mm i.d. with a 0.2 µm film thickness (Supelco) (Reverberi et al, 2012). Fatty acids were identified by comparison of retention times to authentic standards.…”