Influence of sub-lethal antioxidant doses, water potential and temperature on growth, sclerotia, aflatoxins and aflD (=nor-1) expression by Aspergillus flavus RCP08108.
Effects of interacting conditions of sub-lethal levels of antioxidants, water potential (Ψ) and temperature were evaluated on growth, sclerotial characteristics, aflatoxin B(1) (AFB(1)) production and aflD (=nor-1) gene expression by Aspergillus flavus strain RCP08108. These studies were carried out on peanut meal extract agar osmotically modified to -2.8,-7.1, -9.9 and -16.0 MPa and incubated at 28 and 20°C. The food grade antioxidants added were butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) at (1+1 mM-M1) and (5+5 mM-M2). To relate the aflD expression after toxigenic A. flavus grew under interacting stress conditions, real-time PCR was used. Antioxidant mixtures caused a higher and significant (p<0.001) reduction in growth rate. The major impact on size and volume sclerotia was produced by Ψ; followed by antioxidant mixtures. High AFB(1) levels were observed in response to the M1 applied at -7.1 MPa. Induction of the aflD gene was observed in response to the M1 treatment at -2.8, -7.1 and -9.9 MPa; but significant decreases of AFB(1) production and aflD transcripts were observed; when the fungus grew in the presence of the M2 treatment. These results showed that it is necessary to apply food-grade antioxidants into the peanut storage system at levels higher than 5 mM. This is an important tool to avoid sub-lethal antioxidant doses that can lead to fungal growth, increase resistance structures, and stimulate aflD gene expression and AFB(1) accumulation in this substrate.
Departamento de Microbiología e Inmunología, Facultad de Ciencias Exactas Físico Químicas y Naturales, Universidad Nacional de Río Cuarto, Río Cuarto, Córdoba, Argentina.
María Alejandra
MA
Passone
Laura Cristina
LC
Rosso
Miriam
M
Etcheverry
D000348:Aflatoxins / Q000378:metabolism*; D000975:Antioxidants / Q000378:metabolism*; D001231:Aspergillus flavus / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D003470:Culture Media / Q000737:chemistry; D005516:Food Microbiology; D015870:Gene Expression / Q000187:drug effects* / Q000528:radiation effects*; D020869:Gene Expression Profiling; D060888:Real-Time Polymerase Chain Reaction; D013696:Temperature; D014867:Water / Q000737:chemistry*
D000348:Aflatoxins; D000975:Antioxidants; D003470:Culture Media; D014867:Water