scholarly journals Effect of Carotenoids on Aflatoxin B1 Synthesis by Aspergillus flavus

1997 ◽  
Vol 87 (8) ◽  
pp. 814-821 ◽  
Author(s):  
Robert A. Norton
Keyword(s):  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Culture Method ◽  
Aflatoxin Biosynthesis ◽  
Ring Type ◽  
Yellow Corn ◽  
Norsolorinic Acid ◽  
Aflatoxin B ◽  
Hydroxy Groups ◽  
Β Carotene

Carotenes and xanthophylls occurring in yellow corn and related terpenoids were tested for their effect on growth and aflatoxin B1 production by Aspergillus flavus NRRL 3357, using the suspended disc culture method. Aflatoxin synthesis was inhibited at concentrations of β-carotene, lutein, and zeaxanthin comparable to those found in the horny endosperm of mature corn. Usually growth was not significantly affected. Inhibition of aflatoxin biosynthesis was greater for compounds with an α-ionone-type ring (α-carotene, lutein, or α-ionone) compared with compounds with a β-ionone ring. The presence of hydroxy groups on the rings tended to decrease inhibition, but did not override the effect of the ring type; lutein was similar to α-carotene and zeaxanthin was similar to β-carotene in inhibition. A mutant accumulating norsolorinic acid (NA), A. parasiticus SRRC 162, incubated with α-carotene produced reduced levels of both NA and aflatoxin, indicating that inhibition occurred before NA. Additional A. flavus strains tested against 50 μg/ml of β-carotene had 89 to 96% inhibition, which was significantly more sensitive than NRRL 3357. A. parasiticus strains were less sensitive and generally had similar or lower inhibition than NRRL 3357. The results indicate that the presence of carotenoids in endosperm may decrease the amount of aflatoxin produced by A. flavus.

scholarly journals Impact of Silver Nanoparticles on Gene Expression in Aspergillus Flavus Producer Aflatoxin B1

2018 ◽  
Vol 6 (4) ◽  
pp. 600-605 ◽  
Author(s):  
Mohamed Mahmoud Deabes ◽  
Wagdy Khalil Bassaly Khalil ◽  
Ashraf Gamil Attallah ◽  
Tarek Ahmed El-Desouky ◽  
Khayria Mahmoud Naguib
Keyword(s):  
Silver Nanoparticles ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Inhibitory Effect ◽  
Aflatoxin Biosynthesis ◽  
Qrt Pcr ◽  
Methyltransferase Gene ◽  
Polymerase Chain ◽  
Yeast Extract Sucrose ◽  
Quantitative Pcr Assay

AIM: In this study, we evaluated the effect of silver nanoparticles (AgNPs) on the production of aflatoxin B1 (AFB1) through assessment the transcription activity of aflatoxin biosynthesis pathway genes in Aspergillus flavus ATCC28542.MATERIAL AND METHODS: The mRNAs were quantitative by Real Time-polymerase chain reaction (qRT-PCR) of A. flavus grown in yeast extract sucrose (YES) medium containing AgNPs. Specific primers that are involved in the AFB1 biosynthesis which highly specific to A. flavus, O-methyltransferase gene (omt-A), were designed and used to detect the fungus activity by quantitative PCR assay. The AFB1 production (from A. flavus growth) which effected by AgNPs were measured in YES medium by high-pressure liquid chromatography (HPLC).RESULTS: The AFB1 produced by A. flavus have the highest reduction with 1.5 mg -100 ml of AgNPs were added in media those records 88.2%, 67.7% and 83.5% reduction by using AgNP HA1N, AgNP HA2N and AgNP EH, respectively. While on mycelial growth give significantly inhibitory effect. These results have been confirmed by qRT-PCR which showed that culture of A. flavus with the presence of AgNPs reduced the expression levels of omt-A gene.CONCLUSION: Based on the results of the present study, AgNPs inhibit growth and AFB1 produced by Aspergillus flavus ATCC28542. This was confirmed through RT-PCR approach showing the effect of AgNPs on omt-A gene involved in aflatoxin biosynthesis.

scholarly journals Osmotic-Adaptation Response of sakA/hogA Gene to Aflatoxin Biosynthesis, Morphology Development and Pathogenicity in Aspergillus flavus

Toxins ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 41 ◽  
Author(s):  
Elisabeth Tumukunde ◽  
Ding Li ◽  
Ling Qin ◽  
Yu Li ◽  
Jiaojiao Shen ◽  
...  
Keyword(s):  
Osmotic Stress ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Wall Stress ◽  
Mitogen Activated Protein Kinase ◽  
Human Beings ◽  
Aflatoxin Biosynthesis ◽  
Wild Type ◽  
Adaptation Response ◽  
Seed Crops

Aspergillus flavus is one of the fungi from the big family of Aspergillus genus and it is capable of colonizing a large number of seed/crops and living organisms such as animals and human beings. SakA (also called hogA/hog1) is an integral part of the mitogen activated protein kinase signal of the high osmolarity glycerol pathway. In this study, the AfsakA gene was deleted (∆AfsakA) then complemented (∆AfsakA::AfsakA) using homologous recombination and the osmotic stress was induced by 1.2 mol/L D-sorbital and 1.2 mol/L sodium chloride. The result showed that ∆AfsakA mutant caused a significant influence on conidial formation compared to wild-type and ∆AfsakA::AfsakA strains. It was also found that AfsakA responds to both the osmotic stress and the cell wall stress. In the absence of osmotic stress, ∆AfsakA mutant produced more sclerotia in contrast to other strains, whereas all strains failed to generate sclerotia under osmotic stress. Furthermore, the deletion of AfsakA resulted in the increase of Aflatoxin B1 production compared to other strains. The virulence assay on both maize kernel and peanut seeds showed that ∆AfsakA strain drastically produced more conidia and Aflatoxin B1 than wild-type and complementary strains. AfSakA-mCherry was located to the cytoplasm in the absence of osmotic stress, while it translocated to the nucleus upon exposure to the osmotic stimuli. This study provides new insights on the development and evaluation of aflatoxin biosynthesis and also provides better understanding on how to prevent Aspergillus infections which would be considered the first step towards the prevention of the seeds damages caused by A. flavus.

Resistance to Aflatoxin Contamination in Corn as Influenced by Relative Humidity and Kernel Germination

1996 ◽  
Vol 59 (3) ◽  
pp. 276-281 ◽  
Author(s):  
B. Z. GUO ◽  
J. S. RUSSIN ◽  
R. L. BROWN ◽  
T. E. CLEVELAND ◽  
N. W. WIDSTROM
Keyword(s):  
Relative Humidity ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Resistance Mechanisms ◽  
Aflatoxin Contamination ◽  
Aflatoxin Biosynthesis ◽  
Aflatoxin Accumulation ◽  
Moisture Conditions ◽  
Very High ◽  
Fungus Growth

Kernels of corn population GT-MAS:gk, resistant to aflatoxin B1 production by Aspergillus flavus, and susceptible Pioneer hybrid 3154 were tested for aflatoxin when incubated under different relative humidities (RH). High aflatoxin levels were not detected in either genotype at RH < 91%. Resistance in GT-MAS:gk was consistent across all RH levels (91 to 100%) at which significant aflatoxin accumulation was detected. Aflatoxin levels in GT-MAS:gk averaged about 98% less than those in susceptible Pioneer 3154, which suggests that storage of this or other genotypes with similar resistance mechanisms may be possible under moisture conditions less exacting than are required with susceptible hybrids. Results for fungus growth and sporulation ratings on kernel surfaces were similar to those for aflatoxin levels. When kernels of both genotypes were preincubated 3 days at 100% RH prior to inoculation with A. flavus, germination percentages increased to very high levels compared to those of kernels that were not preincubated. In preincubated kernels aflatoxin levels remained consistently low in GT-MAS:gk but decreased markedly (61%) in Pioneer 3154. When eight susceptible hybrids were evaluated for aflatoxin accumulation in preincubated kernels, seven of these supported significantly lower toxin levels than kernels not subjected to preincubation. Average reduction across hybrids was 83%, and reductions within hybrids ranged from 68 to 96%. Preincubated kernels of one susceptible hybrid (Deltapine G-4666) supported aflatoxin levels comparable to those in resistant GT-MAS:gk. Data suggest that an inhibitor of aflatoxin biosynthesis may be induced during kernel germination. Possible mechanisms for embryo effects on resistance to aflatoxin accumulation are discussed.

scholarly journals Interaction Between Certain Moulds and Aflatoxin B1 Producer Aspergillus Flavus NRRL 3251

2007 ◽  
Vol 58 (4) ◽  
pp. 429-434 ◽  
Author(s):  
Zdenka Cvetnić ◽  
Stjepan Pepeljnjak
Keyword(s):  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Aflatoxin Production ◽  
Toxin Production ◽  
Airborne Fungi ◽  
Biotic Interaction ◽  
Detectable Amount ◽  
Single Culture ◽  
Aflatoxin B ◽  
Yeast Extract Sucrose

Interaction Between Certain Moulds and Aflatoxin B1ProducerAspergillus FlavusNRRL 3251The objective of this study was to evaluate biotic interaction between some mould species and active producer of aflatoxin B1Aspergillus flavusNRRL 3251, co-cultured in yeast-extract sucrose (YES) broth. Twenty-five mould strains ofAlternariaspp.,Cladosporiumspp.,Mucorspp.,A. flavusandA. niger, used as biocompetitive agents, were isolated from outdoor and indoor airborne fungi, scrapings of mouldy household walls, and from stored and post-harvest maize. Aflatoxin B1was extracted from mould biomasses with chloroform and detected using the multitoxin TLC method. The results confirm antagonistic interaction between all strains tested. WithAlternariaspp. andCladosporiumspp., aflatoxin B1production decreased 100 %, compared to detection in a single culture ofA. flavusNRRL 3251 (Cmean=18.7 μg mL-1). In mixed cultures withMucorspp., aflatoxinB1levels dropped to (5.6-9.3) μg mL-1, and the inhibition was from 50 % to 70 %. Four of five aflatoxin non-producing strains ofA. flavusinterfered with aflatoxin production in mixed culture, and reduced AFB1productivity by 100 %. One strain showed a lower efficacy in inhibiting AFB1production (80 %) with a detectable amount of AFB13.7 μg mL-1when compared to control. A decrease in toxin production was also observed in dual cultivation withA. nigerstrains. It resulted in 100 % reduction in three strains), 90 % reduction in one strain (Cmean=1.9 μg mL-1) and 80 % reduction in one strain (Cmean=3.7 μg mL-1) inhibition.

β-Carotene inhibition of aflatoxin biosynthesis among Aspergillus flavus genotypes from Illinois corn

Mycoscience ◽  
1998 ◽  
Vol 39 (2) ◽  
pp. 167-172 ◽  
Author(s):  
Donald T. Wicklow ◽  
Robert A. Norton ◽  
Cesaria E. McAIpin
Keyword(s):  
Aspergillus Flavus ◽  
Aflatoxin Biosynthesis ◽  
Β Carotene

scholarly journals The PHD Transcription Factor Rum1 Regulates Morphogenesis and Aflatoxin Biosynthesis in Aspergillus flavus

Toxins ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 301 ◽  
Author(s):  
Yule Hu ◽  
Guang Yang ◽  
Danping Zhang ◽  
Yaju Liu ◽  
Yu Li ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Homologous Recombination ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Biological Function ◽  
Biological Synthesis ◽  
Deletion Mutants ◽  
Aflatoxin Biosynthesis

Aspergillus flavus produces mycotoxins especially aflatoxin B1 and infects crops worldwide. As a PHD transcription factor, there is no report on the role of Rum1 in the virulence of Aspergillus spp. yet. This study explored the biological function of Rum1 in A. flavus through the construction of rum1 deletion mutants and rum1 complementation strains with the method of homologous recombination. It was found, in the study, that Rum1 negatively regulates conidiation through abaA and brlA, positively regulates sclerotia formation through nsdC, nsdD, and sclR, triggers aflatoxin biological synthesis, and enhances the activity of amylase. Our findings suggested that Rum1 plays a major role in the growth of mycelia, conidia, and sclerotia production along with aflatoxin biosynthesis in A. flavus.

Mycotoxins - Their Biosynthesis in Fungi: Aflatoxins and other Bisfuranoids

1979 ◽  
Vol 42 (10) ◽  
pp. 805-809 ◽  
Author(s):  
J. W. BENNETT ◽  
L. S. LEE
Keyword(s):  
Experimental Data ◽  
Secondary Metabolites ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Aspergillus Parasiticus ◽  
Fungal Metabolites ◽  
Aflatoxin Biosynthesis ◽  
Mechanism Of Formation ◽  
13C Labeling

Aflatoxins are a family of highly toxic and carcinogenic secondary metabolites produced by certain strains of Aspergillus flavus and Aspergillus parasiticus. Biosynthetically, the aflatoxins are produced by a polyketide pathway. Most of the experimental data on aflatoxin biosynthesis are derived from 14C- and 13C-labeling experiments and use of blocked mutants. These data indicate that the general steps in aflatoxin biosynthesis are acetate → anthraquinones → sterigmatocystin → aflatoxin B1. Many details of the pathway remain unresolved; it is hoped that further research, particularly with cell-free systems, will improve our understanding of the mechanism of formation of these important fungal metabolites.

scholarly journals The Conserved MAP Kinase MpkB Regulates Development and Sporulation without Affecting Aflatoxin Biosynthesis in Aspergillus flavus

2020 ◽  
Vol 6 (4) ◽  
pp. 289
Author(s):  
Sang-Cheol Jun ◽  
Jong-Hwa Kim ◽  
Kap-Hoon Han
Keyword(s):  
Map Kinase ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Aflatoxin Biosynthesis ◽  
Wild Type ◽  
Growth Defects ◽  
Expression Of Genes ◽  
Growth Development ◽  
Kinase Signaling Pathway ◽  
Map Kinase Signaling Pathway

In eukaryotes, the MAP kinase signaling pathway plays pivotal roles in regulating the expression of genes required for growth, development, and stress response. Here, we deleted the mpkB gene (AFLA_034170), an ortholog of the Saccharomyces cerevisiae FUS3 gene, to characterize its function in Aspergillus flavus, a cosmopolitan, pathogenic, and aflatoxin-producing fungus. Previous studies revealed that MpkB positively regulates sexual and asexual differentiation in Aspergillus nidulans. In A. flavus, mpkB deletion resulted in an approximately 60% reduction in conidia production compared to the wild type without mycelial growth defects. Moreover, the mutant produced immature and abnormal conidiophores exhibiting vesicular dome-immaturity in the conidiophore head, decreased phialide numbers, and very short stalks. Interestingly, the ΔmpkB mutant could not produce sclerotia but produced aflatoxin B1 normally. Taken together, these results suggest that the A. flavus MpkB MAP kinase positively regulates conidiation and sclerotia formation but is not involved in the production of secondary metabolites such as aflatoxin B1.

scholarly journals Mimosa tenuiflora Aqueous Extract: Role of Condensed Tannins in Anti-Aflatoxin B1 Activity in Aspergillus flavus

Toxins ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 391
Author(s):  
Christopher Hernandez ◽  
Laura Cadenillas ◽  
Anwar El Maghubi ◽  
Isaura Caceres ◽  
Vanessa Durrieu ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Aqueous Extract ◽  
Aflatoxin B1 ◽  
Condensed Tannins ◽  
Fungal Growth ◽  
Oxidation Reactions ◽  
Expression Of Genes ◽  
Dependent Inhibition ◽  
Interesting Candidate ◽  
Mimosa Tenuiflora

Aflatoxin B1 (AFB1) is a potent carcinogenic mycotoxin that contaminates numerous crops pre- and post-harvest. To protect foods and feeds from such toxins without resorting to pesticides, the use of plant extracts has been increasingly studied. The most interesting candidate plants are those with strong antioxidative activity because oxidation reactions may interfere with AFB1 production. The present study investigates how an aqueous extract of Mimosa tenuiflora bark affects both the growth of Aspergillus flavus and AFB1 production. The results reveal a dose-dependent inhibition of toxin synthesis with no impact on fungal growth. AFB1 inhibition is related to a down-modulation of the cluster genes of the biosynthetic pathway and especially to the two internal regulators aflR and aflS. Its strong anti-oxidative activity also allows the aqueous extract to modulate the expression of genes involved in fungal oxidative-stress response, such as msnA, mtfA, atfA, or sod1. Finally, a bio-guided fractionation of the aqueous extract demonstrates that condensed tannins play a major role in the anti-aflatoxin activity of Mimosa tenuiflora bark.

scholarly journals Impacts of Climate Change Interacting Abiotic Factors on Growth, aflD and aflR Gene Expression and Aflatoxin B1 Production by Aspergillus flavus Strains In Vitro and on Pistachio Nuts

Toxins ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 385
Author(s):  
Alaa Baazeem ◽  
Alicia Rodriguez ◽  
Angel Medina ◽  
Naresh Magan
Keyword(s):  
Climate Change ◽  
Gene Expression ◽  
Water Stress ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Abiotic Factors ◽  
Pistachio Nuts ◽  
Significant Difference ◽  
Spoilage Fungi

Pistachio nuts are an important economic tree nut crop which is used directly or processed for many food-related activities. They can become colonized by mycotoxigenic spoilage fungi, especially Aspergillus flavus, mainly resulting in contamination with aflatoxins (AFs), especially aflatoxin B1 (AFB1). The prevailing climate in which these crops are grown changes as temperature and atmospheric CO2 levels increase, and episodes of extreme wet/dry cycles occur due to human industrial activity. The objectives of this study were to evaluate the effect of interacting Climate Change (CC)-related abiotic factors of temperature (35 vs. 37 °C), CO2 (400 vs. 1000 ppm), and water stress (0.98–0.93 water activity, aw) on (a) growth (b) aflD and aflR biosynthetic gene expression and (c) AFB1 production by two strains A. flavus (AB3, AB10) in vitro on milled pistachio-based media and when colonizing layers of shelled raw pistachio nuts. The A. flavus strains were resilient in terms of growth on pistachio-based media and the colonisation of pistachio nuts with no significant difference when exposed to the interacting three-way climate-related abiotic factors. However, in vitro studies showed that AFB1 production was significantly stimulated (p < 0.05), especially when exposed to 1000 ppm CO2 at 0.98–0.95 aw and 35 °C, and sometimes in the 37 °C treatment group at 0.98 aw. The relative expression of the structural aflD gene involved in AFB1 biosynthesis was decreased or only slightly increased, relative to the control conditions at elevated CO, regardless of the aw level examined. For the regulatory aflR gene expression, there was a significant (p < 0.05) increase in 1000 ppm CO2 and 37 °C for both strains, especially at 0.95 aw. The in situ colonization of pistachio nuts resulted in a significant (p < 0.05) stimulation of AFB1 production at 35 °C and 1000 ppm CO2 for both strains, especially at 0.98 aw. At 37 °C, AFB1 production was either decreased, in strain AB3, or remained similar, as in strain AB10, when exposed to 1000 ppm CO2. This suggests that CC factors may have a differential effect, depending on the interacting conditions of temperature, exposure to CO2 and the level of water stress on AFB1 production.

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