title: 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.
authors.affiliation: Dipartimento di Biologia Ambientale, Università Sapienza, Roma, Italy. massimo.reverberi@uniroma1.it
authors.forename: Massimo
authors.initials: M
authors.lastname: Reverberi
authors.forename: Marta
authors.initials: M
authors.lastname: Punelli
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Smith
authors.forename: Slaven
authors.initials: S
authors.lastname: Zjalic
authors.forename: Marzia
authors.initials: M
authors.lastname: Scarpari
authors.forename: Valeria
authors.initials: V
authors.lastname: Scala
authors.forename: Giorgia
authors.initials: G
authors.lastname: Cardinali
authors.forename: Nicaela
authors.initials: N
authors.lastname: Aspite
authors.forename: Flavia
authors.initials: F
authors.lastname: Pinzari
authors.forename: Gary A
authors.initials: GA
authors.lastname: Payne
authors.forename: Anna A
authors.initials: AA
authors.lastname: Fabbri
authors.forename: Corrado
authors.initials: C
authors.lastname: Fanelli
mesh_terms: D000348:Aflatoxins / Q000096:biosynthesis*; D000975:Antioxidants / Q000378:metabolism; D001231:Aspergillus flavus / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D001629:Bezafibrate / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects*; D005822:Genetic Vectors; D000960:Hypolipidemic Agents / Q000494:pharmacology; D050356:Lipid Metabolism / Q000187:drug effects; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D020675:Peroxisomes / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D017864:Tombusvirus / Q000235:genetics
chemical_list: D000348:Aflatoxins; D000975:Antioxidants; D005227:Fatty Acids; D005656:Fungal Proteins; D000960:Hypolipidemic Agents; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase; D001629:Bezafibrate