Genetic Interaction of Global Regulators AflatfA and AflatfB Mediating Development, Stress Response and Aflatoxins B1 Production in Aspergillus flavus

Abstract

Aspergillus flavus produces carcinogenic and mutagenic aflatoxins, which cause economic losses and risk of food safety by contaminating grains, food and feed. In this study, we characterized two bZIP transcription factors, AflatfA and AflatfB, and their genetic interaction. Compared to the wild type (WT), AflatfA deletion and AflatfA and AflatfB double deletion both caused retarded vegetative growth of mycelia. Relative to WT, the AflatfA deletion strain (ΔAflatfA) and AflatfA and AflatfB double deletion strain (ΔAflatfAΔAflatfB) produced more sclerotia, whereas the AflatfB deletion strain (ΔAflatfB) produced less sclerotia. After 4 °C preservation and incubation at 50 °C, conidia viability dramatically decreased in the ΔAflatfA and ΔAflatfAΔAflatfB but ΔAflatfB mutants, whereas conidia viability of the ΔAflatfAΔAflatfB strain was higher after storage at 4 °C than in AflatfA mutant. Conidia of ΔAflatfA, ΔAflatfB and ΔAflatfAΔAflatfB strains significantly increased in sensitivity to H2O2 in comparison with WT. Compared to WT, the mycelium of ΔAflatfA and ΔAflatfB strains were more sensitive to H2O2; conversely, the ΔAflatfAΔAflatfB strain showed less sensitivity to H2O2. ΔAflatfA and ΔAflatfAΔAflatfB strains displayed less sensitivity to the osmotic reagents NaCl, KCl and Sorbitol, in comparison with WT and ΔAflatfB strains. When on YES medium and hosts corn and peanut, ΔAflatfA and ΔAflatfAΔAflatfB strains produced less aflatoxin B1 (AFB1) than ΔAflatfB, and the AFB1 yield of ΔAflatfB was higher than that of WT. When WT and mutants were inoculated on corn and peanut, the ΔAflatfA and ΔAflatfAΔAflatfB but not ΔAflatfB mutants produced less conidia than did WT. Taken together, this study reveals that AflatfA controls more cellular processes, and the function of AflatfA is stronger than that of AflatfB when of the same process is regulated, except the response to H2O2, which might result from the effect of AflatfA on the transcriptional level of AflatfB.

Effect of some Organic Acids and Plants Extract on Growth of Aspergillus flavus

“…A.flavus, is the major producer of aflatoxins, which are secondary metabolites found in food and agri-food, particularly in peanuts and corn. Thus, limiting A. flavus is a useful strategy for lowering aflatoxins' contamination of food directly from the source [6,7]. Due to the substantial damage caused by A. flavus to agricultural products, it is imperative to effectively control the pathogen.…”

Efficient Inhibition of Aspergillus flavus to Reduce Aflatoxin Contamination on Peanuts over Ag-Loaded Titanium Dioxide

“…Aflatoxins, with high toxicity, teratogenicity, and carcinogenicity, have been regarded as the most toxic mycotoxins found in food and agri-food [ 6 , 7 , 8 ], which not only threaten human health, but also can lead to huge economic losses [ 9 , 10 , 11 , 12 , 13 ]. Aflatoxins are secondary metabolites, mainly produced by Aspergillus flavus (A. flavus) in food and agri-food, especially peanuts and corn [ 14 , 15 ]. Therefore, controlling A. flavus is a meaningful approach to reducing the contamination of aflatoxins in food and agri-food from the source.…”