Complex regulation of the aflatoxin biosynthesis gene cluster of Aspergillus flavus in relation to various combinations of water activity and temperature

Schmidt‐Heydt, Markus; Abdel-Hadi, Ahmed; Magan, Naresh; Geisen, Rolf

doi:10.1016/j.ijfoodmicro.2009.07.026

Cited by 152 publications

(146 citation statements)

References 31 publications

(33 reference statements)

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“…This showed that both temperature and a w influenced their relative expression. Schmidt-Heydt et al [19,20] showed that the ratio of the regulatory genes aflR and aflS may be important, as a low ratio under certain a w Â temperature levels resulted in low AFB 1 production while higher ratios resulted in significantly higher toxin production in both A. flavus and A. parasiticus. Because of this, we examined the relative activity of two genes (aflD, aflM) present in the early part of the biosynthetic pathway with the regulatory genes in relation to changes in a w and temperature.…”

Section: Discussionmentioning

confidence: 99%

“…The A. flavus strain (NRRL 3357) was previously used in molecular ecology studies [19]. This was kindly provided by Dr D. Bhatnagar, USDA, New Orleans, LA, USA.…”

Section: Fungal Strain Usedmentioning

confidence: 99%

“…It was stored at 48C and sub-cultured on a 2 per cent maize meal agar when required. It has a known AFB 1 production capacity [19].…”

Section: Fungal Strain Usedmentioning

confidence: 99%

“…The ratio of the key regulatory genes (aflR and aflS [¼AflJ]) being important in encoding the enzymes in the biosynthetic pathway of both A. flavus and A. parasiticus [19,20]. Other studies have also demonstrated the impact that such environmental factors may have, especially marginal stress conditions, on gene cluster expression and phenotypic toxin production for a number of species [21].…”

Section: Introductionmentioning

confidence: 99%

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A systems approach to model the relationship between aflatoxin gene cluster expression, environmental factors, growth and toxin production by Aspergillus flavus

Abdel-Hadi

Schmidt‐Heydt

Parra‐Saldívar

et al. 2011

J. R. Soc. Interface.

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135

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A microarray analysis was used to examine the effect of combinations of water activity (a w , 0.995-0.90) and temperature (20 -428C) on the activation of aflatoxin biosynthetic genes (30 genes) in Aspergillus flavus grown on a conducive YES (20 g yeast extract, 150 g sucrose, 1 g MgSO 4 . 7H 2 O) medium. The relative expression of 10 key genes (aflF, aflD, aflE, aflM, aflO, aflP, aflQ, aflX, aflR and aflS) in the biosynthetic pathway was examined in relation to different environmental factors and phenotypic aflatoxin B 1 (AFB 1 ) production. These data, plus data on relative growth rates and AFB 1 production under different a w Â temperature conditions were used to develop a mixed-growth-associated product formation model. The gene expression data were normalized and then used as a linear combination of the data for all 10 genes and combined with the physical model. This was used to relate gene expression to a w and temperature conditions to predict AFB 1 production. The relationship between the observed AFB 1 production provided a good linear regression fit to the predicted production based in the model. The model was then validated by examining datasets outside the model fitting conditions used (378C, 408C and different a w levels). The relationship between structural genes (aflD, aflM) in the biosynthetic pathway and the regulatory genes (aflS, aflJ) was examined in relation to a w and temperature by developing ternary diagrams of relative expression. These findings are important in developing a more integrated systems approach by combining gene expression, ecophysiological influences and growth data to predict mycotoxin production. This could help in developing a more targeted approach to develop prevention strategies to control such carcinogenic natural metabolites that are prevalent in many staple food products. The model could also be used to predict the impact of climate change on toxin production.

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Section: Discussionmentioning

confidence: 99%

“…The A. flavus strain (NRRL 3357) was previously used in molecular ecology studies [19]. This was kindly provided by Dr D. Bhatnagar, USDA, New Orleans, LA, USA.…”

Section: Fungal Strain Usedmentioning

confidence: 99%

“…It was stored at 48C and sub-cultured on a 2 per cent maize meal agar when required. It has a known AFB 1 production capacity [19].…”

Section: Fungal Strain Usedmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A systems approach to model the relationship between aflatoxin gene cluster expression, environmental factors, growth and toxin production by Aspergillus flavus

Abdel-Hadi

Schmidt‐Heydt

Parra‐Saldívar

et al. 2011

J. R. Soc. Interface.

Self Cite

135

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“…As other countries found within the tropics, aflatoxin contamination in food commodities from Burundi and Eastern DRC can be attributed to high temperatures and drought conditions driven by climate change, resulting in crop stress which favors A. flavus infection in the production field and proliferation during postharvest period (Bandyopadhyay et al., 2016; Kamika, Koto‐te‐Nyiwa, & Tekere, 2016; Kamika & Takoy, 2011; Paterson & Lima, 2010; Schmidt‐Heydt, Abdel‐Hadi, Magan, & Geisen, 2009). In addition, high aflatoxin contamination levels can be compounded by other farm practice factors, including poor weeding, infertile soils particularly in Burundi, poor crop rotation, high planting densities, and delayed time of harvesting.…”

Section: Resultsmentioning

confidence: 99%

Occurrence of aflatoxin in agricultural produce from local markets in Burundi and Eastern Democratic Republic of Congo

Udomkun

Mutegi

Wossen

et al. 2018

Food Science & Nutrition

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Aflatoxins are noxious secondary metabolites, of certain fungal species, found in food and feed. Contamination of a commodity with aflatoxins is associated with production and storage losses, and subsequently less food availability. Aflatoxins can also pose human health risks and represent a barrier to the development of trade, in both domestic and international markets. In this study, samples of cassava, maize, groundnut, beans, soybean, sorghum and milk, and their processed products were collected from local markets in Burundi and Eastern DRC. In order to investigate the levels of aflatoxin, crop samples were analyzed using a single step lateral flow immunochromatographic assay (Reveal Q+), while enzyme‐linked immune‐sorbent assay (ELISA) was used to analyze aflatoxin‐M1 in milk, yogurt, and cheese samples. The results revealed the presence of aflatoxins in all samples from both countries, with levels ranging from 1.3 to 2,410 μg/kg. Samples collected from Burundi contained relatively higher (p > 0.0.5) levels of aflatoxins. In 51% of all the crops samples, total aflatoxin contamination was above the EU maximum tolerable level of 4 μg/kg. Processed products, particularly from groundnut, maize, and sorghum, had the highest levels of aflatoxin contamination when compared to unprocessed grain. With regard to milk and dairy products, the level of aflatoxin‐M1 ranged from 4.8 to 261.1 ng/kg. Approximately 29% of milk and yogurt samples had aflatoxin‐M1 higher than the EU regulatory limit of 50 ng/kg, whereas 20% of cheese samples were found to be contaminated at levels higher than the maximum limit of 250 ng/kg. These results can serve as the basis for pre‐ and postharvest approaches to reduce aflatoxin contamination in agricultural commodities in Burundi and Eastern DRC in order to reduce health risk, avoid reduced production in livestock, and open up export markets.

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Aflatoxins in food systems: recent advances in toxicology, biosynthesis, regulation and mitigation through green nanoformulations

2022

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Aflatoxins are hepatocarcinogenic and immunosuppressive mycotoxins mainly synthesized by Aspergillus flavus, A. parasiticus and A. nomius in food systems, causing negative health impacts to humans and other organisms. Aflatoxins contaminate most of the agri‐products of tropical and subtropical regions due to hot and humid conditions and persist in food items even after food processing steps, causing major threat towards the food security. Different physical and chemical strategies have been applied to mitigate aflatoxin contamination. However, negative impacts of chemical preservatives towards health and environment limit their practical applicability. In this regard, plant‐based preservatives, due to their economical, eco‐friendly and safer profile, are considered as a sustainable approach towards food safety. Incorporation of nanotechnology would enhance the bio‐efficacy of green preservatives by overcoming some of their major challenges, such as volatility. The present review deals with recent information on toxicology and molecular and enzymatic regulatory pathways in the biosynthesis of aflatoxins in food systems. A proper understanding of the role of different genes and regulatory proteins may provide novel preventive strategies for aflatoxin detoxification and also in development of aflatoxin‐resistant food items. The review also emphasizes the role of green nanoformulations as a sustainable approach towards the management of aflatoxins in food systems. In addition, some technological challenges of green nanotechnology have also been discussed in this review, along with highlighting some future perspectives. © 2022 Society of Chemical Industry.

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Complex regulation of the aflatoxin biosynthesis gene cluster of Aspergillus flavus in relation to various combinations of water activity and temperature

Cited by 152 publications

References 31 publications

A systems approach to model the relationship between aflatoxin gene cluster expression, environmental factors, growth and toxin production by Aspergillus flavus

A systems approach to model the relationship between aflatoxin gene cluster expression, environmental factors, growth and toxin production by Aspergillus flavus

Occurrence of aflatoxin in agricultural produce from local markets in Burundi and Eastern Democratic Republic of Congo

Aflatoxins in food systems: recent advances in toxicology, biosynthesis, regulation and mitigation through green nanoformulations

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