Isolation of Aflatoxigenic Aspergillus flavus from Animal-Feed and Exploration of the Genetic Basis of Aflatoxin Biosynthesis

Aspergillus flavus is an opportunistic pathogen of oilseed crops such as maize, peanut, cottonseed, and tree nuts and produces carcinogenic secondary metabolites known as aflatoxins during seed colonization. Aflatoxin contamination not only reduces the value of the produce but also is a health hazard to humans and animals. Previously, we observed inhibition of A. flavus aflatoxin biosynthesis upon exposure to the marine bacterium, Vibrio gazogenes (Vg). In this study, we used RNA sequencing to examine the transcriptional profiles of A. flavus treated with both live and heat-inactivated dead Vg and control samples. Fungal biomass, total accumulated aflatoxins, and expression profiles of genes constituting secondary metabolite biosynthetic gene clusters were determined at 24, 30, and 40 h after treatment. Statistically significant reductions in total aflatoxins were detected in Vg-treated samples as compared to control samples at 40 h. But no statistical difference in fungal biomass was observed upon these treatments. The Vg treatments were most effective on aflatoxin biosynthesis as was reflected in significant downregulation of majority of the genes in the aflatoxin gene cluster including the aflatoxin pathway regulator gene, aflR. Along with aflatoxin genes, we also observed significant downregulation in some other secondary metabolite gene clusters including cyclopiazonic acid and aflavarin, suggesting that the treatment may inhibit other secondary metabolites as well. Finally, a weighted gene correlation network analysis identified an upregulation of ten genes that were most strongly associated with Vg-dependent aflatoxin inhibition and provide a novel start-point in understanding the mechanisms that result in this phenomenon.

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High-Density Genetic Linkage Map Construction Using Whole-Genome Resequencing for Mapping Qtls of Resistance to Aspergillus Flavus Infection in Peanut

10.21203/rs.3.rs-538664/v1 ◽

2021 ◽

Author(s):

Yifei Jiang ◽

Huaiyong Luo ◽

Bolun Yu ◽

Yingbin Ding ◽

Yanping Kang ◽

...

Keyword(s):

Linkage Map ◽

Aspergillus Flavus ◽

Genetic Linkage ◽

Genetic Basis ◽

Genetic Linkage Map ◽

Aflatoxin Contamination ◽

Whole Genome ◽

Genome Resequencing ◽

Favorable Alleles ◽

Whole Genome Resequencing

Abstract Cultivated peanut (Arachis hypogaea L.) is rich in edible oil and protein, which is widely planted around the world as an oil and cash crop. However, aflatoxin contamination seriously affects the quality safety of peanut, hindering the development of peanut industry and threatening consumers’ health. Breeding peanut varieties with resistance to Aspergillus flavus infection is important for control the aflatoxin contamination, and understanding of the genetic basis of resistance is vital to its genetic enhancement. In this study, we report the QTL mapping of resistance to A. flavus infection of a well-known resistant variety J11. A recombination inbred line (RIL) population was constructed by crossing a susceptible variety Zhonghua 16 and J11. Through whole-genome resequencing, a genetic linkage map was constructed with 2,802 recombination bins and an average inter-bin distance of 0.58 cM. Combined with phenotypic data of infection index in four consecutive years, six novel resistant QTLs were identified and they explained 5.03-10.87% phenotypic variances. The favorable alleles of five QTLs were from J11 while that of one QTL were from Zhonghua 16. The pyramiding of these favorable alleles significantly improved the resistance to A. flavus infection. These results could contribute greatly to understanding of genetic basis of A. flavus resistance and could be meaningful in further resistance improvement in peanut.

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Inhibition of Aflatoxin Biosynthesis by Organophosphorus Compounds

Journal of Food Protection ◽

10.4315/0362-028x-43.5.381 ◽

1980 ◽

Vol 43 (5) ◽

pp. 381-384 ◽

Cited By ~ 23

Author(s):

M. F. DUTTON ◽

M. S. ANDERSON

Keyword(s):

Aspergillus Flavus ◽

Organophosphorus Compound ◽

Organophosphorus Compounds ◽

Culture Fluid ◽

Aflatoxin Production ◽

The Other ◽

Aflatoxin Biosynthesis ◽

Inhibition Effect ◽

Type Activity ◽

Acetate Derivative

The effect of a range of organophosphorus and various other compounds on production of aflatoxin by Aspergillus flavus was investigated. Five organophosphorus compounds - Chlormephos, Ciodrin, Naled, Phosdrin and Trichlorphon- at concentrations of 20 and 100 μg/ml of culture fluid were found to have activity similar to Dichlorvos, in that they lowered the level of aflatoxin produced and caused formation of several anthraquinone pigments. Two of these pigments have not previously been described, one was named Versicol and a suggested structure is presented, whilst the other compound was shown to be its acetate derivative. A rationale is suggested for the required elements of structure, which are necessary for an organophosphorus compound to have Dichlorvos-type activity. Two unrelated compounds, ammonium nitrate and Tridecanone were also found to elicit Dichlorvos-type activity. It is likely that tridecanone or its breakdown products competitively inhibit enzymes involved in aflatoxin biosynthesis. It is possible that this inhibition effect explains the lowering of aflatoxin production in lipid-rich commodities infected by A. flavus.

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Aspergillus flavus NRRL 35739, a Poor Biocontrol Agent, May Have Increased Relative Expression of Stress Response Genes

Journal of Fungi ◽

10.3390/jof5020053 ◽

2019 ◽

Vol 5 (2) ◽

pp. 53 ◽

Cited By ~ 2

Author(s):

Kayla K. Pennerman ◽

Guohua Yin ◽

Joan W. Bennett ◽

Sui-Sheng T. Hua

Keyword(s):

Stress Response ◽

Aspergillus Flavus ◽

Genetic Basis ◽

Biocontrol Agent ◽

Success Rates ◽

Lower Stress ◽

Relative Expression ◽

Stress Response Genes ◽

Variable Success ◽

Aflatoxin Accumulation

Biocontrol of the mycotoxin aflatoxin utilizes non-aflatoxigenic strains of Aspergillus flavus, which have variable success rates as biocontrol agents. One non-aflatoxigenic strain, NRRL 35739, is a notably poor biocontrol agent. Its growth in artificial cultures and on peanut kernels was found to be slower than that of two aflatoxigenic strains, and NRRL 35739 exhibited less sporulation when grown on peanuts. The non-aflatoxigenic strain did not greatly prevent aflatoxin accumulation. Comparison of the transcriptomes of aflatoxigenic and non-aflatoxigenic A. flavus strains AF36, AF70, NRRL 3357, NRRL 35739, and WRRL 1519 indicated that strain NRRL 35739 had increased relative expression of six heat shock and stress response proteins, with the genes having relative read counts in NRRL 35739 that were 25 to 410 times more than in the other four strains. These preliminary findings tracked with current thought that aflatoxin biocontrol efficacy is related to the ability of a non-aflatoxigenic strain to out-compete aflatoxigenic ones. The slower growth of NRRL 35739 might be due to lower stress tolerance or overexpression of stress response(s). Further study of NRRL 35739 is needed to refine our understanding of the genetic basis of competitiveness among A. flavus strains.

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