Host Induced Gene Silencing Targeting Aspergillus flavus aflM Reduced Aflatoxin Contamination in Transgenic Maize Under Field Conditions

The molecular mechanisms underlying aflatoxin production have been well-studied in strains of the fungus Aspergillus flavus (A. flavus) under artificial conditions. However, aflatoxin biosynthesis has rarely been studied in A. flavus strains isolated from field conditions with different aflatoxin-producing ability. In the present study, tandem mass tag (TMT) labeling and high-performance liquid chromatography (HPLC) coupled with tandem-mass spectrometry analysis were used for proteomic quantification in natural isolates of high- and low-aflatoxin-yield A. flavus strains. Additionally, findings obtained using the TMT-labeling method were validated using the high-resolution multiple reaction monitoring (MRM-HR) method. In total, 4,363 proteins were quantified, among which 1,045 proteins were differentially expressed between the high- and low-aflatoxin-yield A. flavus strains. Bioinformatics analysis showed that the up-regulated proteins were significantly enriched in carbon-related metabolism and the biosynthesis of secondary metabolites, whereas the down-regulated proteins were enriched in oxidative phosphorylation. Moreover, GST proteins were found to be significantly down-regulated in high-yield A. flavus strains; this result contradicted previous findings obtained from A. flavus strains grown under artificial conditions. In summary, our study provides novel insights into aflatoxin regulation in A. flavus under field conditions and could facilitate the development of various strategies for the effective control of aflatoxin contamination in food crops.

Download Full-text

Comparative Susceptibility of Four Experimental Peanut Lines and the Cultivar Florunner to Preharvest Aflatoxin Contamination

Peanut Science ◽

10.3146/pnut.12.2.0006 ◽

1985 ◽

Vol 12 (2) ◽

pp. 70-72 ◽

Cited By ~ 16

Author(s):

P. D Blankenship ◽

R. J Cole ◽

T. H Sanders

Keyword(s):

Aspergillus Flavus ◽

Laboratory Method ◽

Aflatoxin Contamination ◽

Critical Assessment ◽

Field Conditions ◽

Temperature Conditions ◽

Laboratory Screening ◽

Comparative Susceptibility ◽

Moisture Conditions

Abstract Four peanut genotypes, selected as resistant to invasion by Aspergillus flavus in laboratory screening with rehydrated, stored seed and Florunner cultivar were subjected to preharvest drought and temperature conditions conducive to A. flavus invasion and aflatoxin contamination. Preharvest aflatoxin contamination of peanuts has been previously correlated with geocarposphere temperature and moisture conditions during drought. All genotypes tested were highly contaminated with aflatoxin. This study indicates that a critical assessment should be made of the value of using the current laboratory method to select germplasm for resistance to A. flavus invasion and assuming resistance to aflatoxin contamination under field conditions.

Download Full-text

Revisiting an Aspergillus flavus Strain Isolated from an Egyptian Sugarcane Field in 1930

Microorganisms ◽

10.3390/microorganisms8111633 ◽

2020 ◽

Vol 8 (11) ◽

pp. 1633

Author(s):

Mohamed F. Abdallah ◽

Kris Audenaert ◽

Sarah De Saeger ◽

Jos Houbraken

Keyword(s):

Aspergillus Flavus ◽

Short Communication ◽

Aflatoxin Contamination ◽

Type B ◽

Prevention Strategies ◽

Sugarcane Field ◽

Host Pathogen Interaction ◽

Sugarcane Crop ◽

Insight Into ◽

Shed Light

The aflatoxin type B and G producer Aspergillus novoparasiticus was described in 2012 and was firstly reported from sputum, hospital air (Brazil), and soil (Colombia). Later, several survey studies reported the occurrence of this species in different foods and other agricultural commodities from several countries worldwide. This short communication reports on an old fungal strain (CBS 108.30), isolated from Pseudococcus sacchari (grey sugarcane mealybug) from an Egyptian sugarcane field in (or before) 1930. This strain was initially identified as Aspergillus flavus; however, using the latest taxonomy schemes, the strain is, in fact, A. novoparasiticus. These data and previous reports indicate that A. novoparasiticus is strongly associated with sugarcane, and pre-harvest biocontrol approaches with non-toxigenic A. novoparasiticus strains are likely to be more successful than those using non-toxigenic A. flavus strains. Further studies on the association between A. novoparasiticus and Pseudococcus sacchari might shed light on the distribution (and aflatoxin contamination) of this species in sugarcane. Additionally, the interaction between A. novoparasiticus, Pseudococcus sacchari, and sugarcane crop under different scenarios of climate change will be critical in order to get more insight into the host–pathogen interaction and host resistance and propose appropriate prevention strategies to decrease mycotoxin contamination and crop loss due to A. novoparasiticus attack.

Download Full-text

A Novel Niosome-Encapsulated Essential Oil Formulation to Prevent Aspergillus flavus Growth and Aflatoxin Contamination of Maize Grains During Storage

Toxins ◽

10.3390/toxins11110646 ◽

2019 ◽

Vol 11 (11) ◽

pp. 646 ◽

Cited By ~ 6

Author(s):

García-Díaz ◽

Patiño ◽

Vázquez ◽

Gil-Serna

Keyword(s):

Aspergillus Flavus ◽

Fungal Growth ◽

Storage Conditions ◽

Aflatoxin Contamination ◽

Small Scale ◽

Low Concentrations ◽

Oil Formulation ◽

Scale Test ◽

Encapsulation Method

Aflatoxin (AF) contamination of maize is a major concern for food safety. The use of chemical fungicides is controversial, and it is necessary to develop new effective methods to control Aspergillus flavus growth and, therefore, to avoid the presence of AFs in grains. In this work, we tested in vitro the effect of six essential oils (EOs) extracted from aromatic plants. We selected those from Satureja montana and Origanum virens because they show high levels of antifungal and antitoxigenic activity at low concentrations against A. flavus. EOs are highly volatile compounds and we have developed a new niosome-based encapsulation method to extend their shelf life and activity. These new formulations have been successfully applied to reduce fungal growth and AF accumulation in maize grains in a small-scale test, as well as placing the maize into polypropylene woven bags to simulate common storage conditions. In this latter case, the antifungal properties lasted up to 75 days after the first application.

Download Full-text

Modelling the colonisation of maize by toxigenic and non-toxigenic Aspergillus flavus strains: implications for biological control

World Mycotoxin Journal ◽

10.3920/wmj2008.x036 ◽

2008 ◽

Vol 1 (3) ◽

pp. 333-340 ◽

Cited By ~ 17

Author(s):

H. Abbas ◽

R. Zablotowicz ◽

H. Bruns

Keyword(s):

Biological Control ◽

Aspergillus Flavus ◽

Growth Parameters ◽

Biological Control Agent ◽

Cyclopiazonic Acid ◽

Aflatoxin Contamination ◽

Tween 20 ◽

Lag Phase ◽

Gompertz Equation ◽

Aflatoxin Accumulation

To successfully exploit biological control it is desirable to understand how the introduced agent colonises the host and interferes with establishment of the pest. This study assessed field colonisation of maize by Aspergillus flavus strains as biological control agents to reduce aflatoxin contamination. Maize (corn, Zea mays L.) ears were inoculated with A. flavus using a pin-bar technique in 2004 and 2005. Non-aflatoxigenic strains K49 (NRRL 30797) & CT3 (NRRL 30798) and toxigenic F3W4 (NRRL 30798) were compared against a carrier control (0.2% aqueous Tween 20). Ten ears were sampled over 12 to 20 days, visually assessed, and curves fit to a three compartment Gompertz equation or other best appropriate regressions. Aflatoxin was determined by HPLC and cyclopiazonic acid (CPA) by LC/MS. The Gompertz model describes growth parameters, e.g. growth constant, lag phase and maximum colonisation characterised patterns of maize colonisation for most inoculated treatments. Aflatoxin accumulation in maize inoculated with F3W4 was about 35,000 ng/g in 2004 and 2005, with kinetics of aflatoxin accumulation in 2005 well described by the Gompertz equation. Less than 200 ng/g was observed in maize inoculated with strains CT3 & K49 and accumulation was described by a linear or logistic model. Maize inoculated with strains CT3 and F3W4 accumulated a maximum of 220 and 169 µg/kg CPA, respectively, compared to 22 and 0.2 µg/kg in the control and K49 inoculated, respectively. This technique can be used to elucidate colonisation potential of non-toxigenic A. flavus in maize in relation to biological control of aflatoxin. The greatest reduction of aflatoxin and CPA in maize inoculated with strain K49 and Gompertz parameters on colonisation indicates its superiority to CT3 as a biological control agent. The dynamics of maize colonisation by A. flavus strains and subsequent mycotoxin accumulation generated by using the pin-bar technique has implications for characterising the competence of biocontrol strains for reducing aflatoxin contamination.

Download Full-text

Evaluation of resistance to aflatoxin contamination in kernels of maize genotypes using a GFP-expressing Aspergillus flavus strain

World Mycotoxin Journal ◽

10.3920/wmj2012.1497 ◽

2013 ◽

Vol 6 (2) ◽

pp. 151-158 ◽

Cited By ~ 12

Author(s):

K. Rajasekaran ◽

C.M. Sickler ◽

R.L. Brown ◽

J.W. Cary ◽

D. Bhatnagar

Keyword(s):

Fungal Infection ◽

Aspergillus Flavus ◽

Fluorescent Protein ◽

Aflatoxin Contamination ◽

Clear Correlation ◽

Aleurone Layer ◽

Screening Assay ◽

Maize Germplasm ◽

Antifungal Proteins ◽

Green Fluorescent

Resistance or susceptibility of maize inbreds to infection by Aspergillus flavus was evaluated by the kernel screening assay. A green fluorescent protein-expressing strain of A. flavus was used to measure fungal spread and aflatoxin levels in real-time following fungal infection of kernels. Among the four inbreds tested, MI82 showed the most resistance and Ga209 the least. TZAR101 was also resistant to fungal infection, whereas Va35 was susceptible to fungal infection. However, Va35 produced lower aflatoxin levels compared to the susceptible line Ga209. Fluorescence microscopy indicated that the site of entry of the fungus into the kernel was consistently through the pedicel. Entry through the pericarp was never observed in undamaged kernels. In view of these results, incorporation or overexpression of antifungal proteins should be targeted to the pedicel and basal endosperm region in developing kernels. Once the fungus has entered through the pedicel, it spreads quickly through the open spaces between the pericarp and the aleurone layer, ultimately colonising the endosperm and scutellum and, finally, the embryo. A clear correlation was established between fungal fluorescence and aflatoxin levels. This method provides a quick, reliable means of evaluating resistance to A. flavus in undamaged kernels and provides breeders with a rapid method to evaluate maize germplasm.

Download Full-text

In Vitro Activity of Balanites aegyptiaca and Tamarindus indica Fruit Extracts on Growth and Aflatoxigenicity of Aspergillus flavus and A. parasiticus

Journal of Food Research ◽

10.5539/jfr.v2n4p68 ◽

2013 ◽

Vol 2 (4) ◽

pp. 68 ◽

Cited By ~ 1

Author(s):

Saifeldin Ahmed El-nagerabi ◽

Abdulkadir E. Elshafie ◽

Mohamed R. Elamin

Keyword(s):

Aspergillus Flavus ◽

Fungal Growth ◽

Aflatoxin Contamination ◽

Tamarindus Indica ◽

Balanites Aegyptiaca ◽

Total Aflatoxin ◽

Animal Products ◽

Fruit Extracts ◽

Aflatoxin B

Aflatoxin and especially aflatoxin B1 (AFB1) is a carcinogenic secondary metabolite synthesized by certain Aspergillus species. They contaminate natural and processed agricultural and animal products which render them unfit for consumption. The aim of this study was to evaluate the in vitro effects of Balanites aegyptiaca and Tamarindus indica fruit extracts on the growth and aflatoxin secretion of Aspergillus flavus (SQU21) and A. parasiticus (CBS921.7) strains. The two fruit extracts significantly (P < 0.05) reduced aflatoxin and did not inhibit mycelial dry weights of the two Aspergillus strains. At different concentrations of balanites (2.5-10%), the inhibition of total aflatoxin was 49.9-84.8% for A. flavus (SQU21) and 32.1-84.4% for A. parasiticus (CBS921.7), whereas the inhibition of aflatoxin Bwas 38.2-81.4% and 32.8-80.6% for the two strains. Tamarind fruit extract (2.5-7.5%) caused 28.8-84.2% and 40.7-85.5% reductions in total aflatoxin and 37.1-83.5% and 33.9-85.9% in aflatoxin B for the two strains, respectively. None of these extracts inhibited the fungal growth or detoxified synthetic aflatoxin B1. We have concluded that these fruits contain various inhibitors to aflatoxin biosynthesis and secretion. Therefore, they can be used in combination as safe green biopreservatives to combat aflatoxin contamination of food.

Download Full-text

Aspergillus Colonization and Aflatoxin Contamination in Peanut Genotypes with Resistance to Other Fungal Pathogens

Plant Disease ◽

10.1094/pdis.1997.81.12.1429 ◽

1997 ◽

Vol 81 (12) ◽

pp. 1429-1431 ◽

Cited By ~ 8

Author(s):

C. Corley Holbrook ◽

David M. Wilson ◽

Michael E. Matheron ◽

William F. Anderson

Keyword(s):

Drought Stress ◽

Aspergillus Flavus ◽

Fungal Pathogens ◽

Sclerotium Rolfsii ◽

Indirect Selection ◽

Aflatoxin Contamination ◽

White Mold ◽

Mechanisms Of Resistance ◽

Selection Tool ◽

Aspergillus Flavus Group

Indirect selection tools would be valuable in the development of peanut (Arachis hypogaea) cultivars with resistance to aflatoxin contamination. The objective of this study was to determine whether resistance to other fungi could be used as an indirect selection tool for resistance to colonization of peanut by Aspergillus flavus group fungi or aflatoxin contamination. Nine peanut genotypes with resistance to late leaf spot (Cercosporidium personatum) or white mold (Sclerotium rolfsii) were evaluated for 2 years at Tifton, GA, and Yuma, AZ. Plots were subjected to late-season heat and drought stress. None of the genotypes exhibited less colonization of shells or kernels by A. flavus group fungi than cv. Florunner when tested in Georgia or Arizona. None of the genotypes showed a reduced level of aflatoxin contamination in comparison to Florunner at either location. These results indicate that the mechanisms of resistance to other fungi operating in these genotypes are not effective in providing resistance to colonization by A. flavus group fungi or reducing aflatoxin contamination. Therefore, resistance to these fungi cannot be used as an indirect selection tool for resistance to aflatoxin contamination.

Download Full-text

Vibrio gazogenes inhibits aflatoxin production through downregulation of aflatoxin biosynthetic genes in Aspergillus flavus

PhytoFrontiers™ ◽

10.1094/phytofr-09-21-0067-r ◽

2022 ◽

Author(s):

Shyam L. Kandel ◽

Rubaiya Jesmin ◽

Brian M. Mack ◽

Rajtilak Majumdar ◽

Matthew K. Gilbert ◽

...

Keyword(s):

Secondary Metabolites ◽

Secondary Metabolite ◽

Aspergillus Flavus ◽

Fungal Biomass ◽

Expression Profiles ◽

Health Hazard ◽

Gene Clusters ◽

Aflatoxin Contamination ◽

Aflatoxin Biosynthesis ◽

Control Samples

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.

Download Full-text

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.

Download Full-text