scholarly journals Regulation of Morphology, Aflatoxin Production, and Virulence of Aspergillus flavus by the Major Nitrogen Regulatory Gene areA

Toxins ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 718 ◽  
Author(s):  
Opemipo Esther Fasoyin ◽  
Kunlong Yang ◽  
Mengguang Qiu ◽  
Bin Wang ◽  
Sen Wang ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Regulatory Gene ◽  
Nitrogen Sources ◽  
Aflatoxin Production ◽  
Fungal Species ◽  
Complete Medium ◽  
Over Expression ◽  
Oxidative Stresses ◽  
Gata Transcription Factor

Aspergillus flavus is a renowned plant, animal and human pathogen. areA is a global nitrogen regulatory gene of the GATA transcription factor family, shown to be the major nitrogen regulator. In this study, we identified areA in A. flavus and studied its function. The AreA protein contained a signatory zinc finger domain, which is extremely conserved across fungal species. Gene deletion (ΔareA) and over-expression (OE::areA) strains were constructed by homologous recombination to elucidate the role of areA in A. flavus. The ΔareA strain was unable to efficiently utilize secondary nitrogen sources for growth of A. flavus, and it had poorly developed conidiophores, when observed on complete medium, resulting in the production of significantly less conidia than the wild-type strain (WT). Aflatoxin B1 (AFB1) production was reduced in ΔareA compared with the WT strain in most conditions tested, and ΔareA had impaired virulence in peanut seeds. areA also played important roles in the sensitivity of A. flavus to osmotic, cell wall and oxidative stresses. Hence, areA was found to be important for the growth, aflatoxin production and pathogenicity of A. flavus. This work sheds light on the function of areA in the regulation of the nitrogen metabolism of A. flavus, and consequently aims at providing new ways for controlling the crossover pathogen, A. flavus.

Mycoflora and Aflatoxin-Producing Strains in Animal Mixed Feeds

1994 ◽  
Vol 57 (3) ◽  
pp. 256-258 ◽  
Author(s):  
M. L. ABARCA ◽  
M. R. BRAGULAT ◽  
G. CASTELLÁ ◽  
F. J. CABAÑES
Keyword(s):  
Aspergillus Flavus ◽  
Yeast Extract ◽  
Penicillium Chrysogenum ◽  
Fusarium Moniliforme ◽  
Dominant Species ◽  
Aflatoxin Production ◽  
Fungal Species ◽  
Sucrose Medium ◽  
Mixed Feeds ◽  
Yeast Extract Sucrose

The mycoflora of 69 samples of animal mixed feeds were studied. Fungal counts ranged from 102 to 108 CFU/g, the lowest counts corresponding to the samples of rabbit feeds. Seventy-one fungal species belonging to 26 genera were identified. The pre- dominant species were Aspergillus flavus, Fusarium moniliforme, and Penicillium chrysogenum. Thirty-six strains of A. flavus and one strain of A. parasiticus were screened for aflatoxin production in yeast extract-sucrose medium. The final pH, weight of mycelium, and production of aflatoxins were determined after 14 days of incubation. Five strains (13.5%) were aflatoxigenic. No statistical differences were observed in mycelial dry weights and final pH between aflatoxin-producing strains and nonaflatoxigenic strains.

Use of functional genomics to assess the climate change impact on Aspergillus flavus and aflatoxin production

2016 ◽  
Vol 9 (5) ◽  
pp. 665-672 ◽  
Author(s):  
M.K. Gilbert ◽  
B.M. Mack ◽  
G.A. Payne ◽  
D. Bhatnagar
Keyword(s):  
Climate Change ◽  
Functional Genomics ◽  
Aspergillus Flavus ◽  
Pathogenic Fungus ◽  
Regulatory Gene ◽  
Aflatoxin Production ◽  
Toxin Production ◽  
Transcriptomic Response ◽  
Climate Conditions ◽  
Change Impact

Aspergillus flavus is an opportunistic and pathogenic fungus that infects several crops of agricultural importance and under certain conditions may produce carcinogenic mycotoxins. Rising global temperatures, disrupted precipitation patterns and increased CO2 levels that are associated with future climate conditions are expected to impact the growth and toxigenic potential of A. flavus. Both laboratory and real world observations have demonstrated this potential, especially when examining the effects of water availability and temperature. Recent experiments have also established that CO2 may also be affecting toxin production. The application of current technologies in the field of functional genomics, including genomic sequencing, RNA-seq, microarray technologies and proteomics have revealed climate change-related, abiotic regulation of the aflatoxin cluster and influence on the plant-fungus interaction. Furthermore, elevated CO2 levels have been shown to impact expression of the aflatoxin biosynthetic regulatory gene aflR. The use of functional genomics will allow researchers to better understand the underlying transcriptomic response within the fungus to climate change, with a view towards predicting changes in fungal infection and toxin production associated with climate change.

scholarly journals Role of BkdR, a Transcriptional Activator of the SigL-Dependent Isoleucine and Valine Degradation Pathway inBacillus subtilis

1999 ◽  
Vol 181 (7) ◽  
pp. 2059-2066 ◽  
Author(s):  
Michel Debarbouille ◽  
Rozenn Gardan ◽  
Maryvonne Arnaud ◽  
George Rapoport
Keyword(s):  
Catalytic Domain ◽  
Regulatory Gene ◽  
Nitrogen Sources ◽  
Degradation Pathway ◽  
Sigma 54 ◽  
Nutritional Conditions ◽  
New Gene ◽  
Butyrate Kinase ◽  
Branched Chain

ABSTRACT A new gene, bkdR (formerly called yqiR), encoding a regulator with a central (catalytic) domain was found inBacillus subtilis. This gene controls the utilization of isoleucine and valine as sole nitrogen sources. Seven genes, previously called yqiS, yqiT, yqiU,yqiV, bfmBAA, bfmBAB, andbfmBB and now referred to as ptb,bcd, buk, lpd, bkdA1,bkdA2, and bkdB, are located downstream from the bkdR gene in B. subtilis. The products of these genes are similar to phosphate butyryl coenzyme A transferase, leucine dehydrogenase, butyrate kinase, and four components of the branched-chain keto acid dehydrogenase complex: E3 (dihydrolipoamide dehydrogenase), E1α (dehydrogenase), E1β (decarboxylase), and E2 (dihydrolipoamide acyltransferase). Isoleucine and valine utilization was abolished in bcd and bkdR null mutants ofB. subtilis. The seven genes appear to be organized as an operon, bkd, transcribed from a −12, −24 promoter. The expression of the bkd operon was induced by the presence of isoleucine or valine in the growth medium and depended upon the presence of the sigma factor SigL, a member of the sigma 54 family. Transcription of this operon was abolished in strains containing a null mutation in the regulatory gene bkdR. Deletion analysis showed that upstream activating sequences are involved in the expression of the bkd operon and are probably the target ofbkdR. Transcription of the bkd operon is also negatively controlled by CodY, a global regulator of gene expression in response to nutritional conditions.

Inhibitory effect of molybdenum and vanadium salts on aflatoxin B1 synthesis by Aspergillus flavus

1981 ◽  
Vol 27 (9) ◽  
pp. 962-967 ◽  
Author(s):  
C. J. Rabie ◽  
C. J. Meyer ◽  
Laetitia van Heerden ◽  
Annelie Lübben
Keyword(s):  
Trace Elements ◽  
Aspergillus Flavus ◽  
Basal Medium ◽  
Sodium Molybdate ◽  
Aflatoxin Production ◽  
Inhibitory Effect ◽  
Complete Medium ◽  
Ammonium Heptamolybdate ◽  
Vanadium Salts ◽  
Aflatoxin B

The effects of the elements zinc, manganese, iron, copper, molybdenum, and vanadium, added in various salt forms, on mycelial weights and aflatoxin B1 accumulation in the mycelium of Aspergillus flavus were investigated in liquid shake cultures. Ammonium heptamolybdate, when added to a complete medium at concentrations of 50–100 mg/L, appreciably reduced aflatoxin B1 accumulation without affecting growth of the fungus. Sodium molybdate and sodium monovanadate also reduced aflatoxin B1 yields without affecting mycelial growth, but to a lesser extent.The addition of zinc sulphate stimulated aflatoxin B1 production in all media used. The influence of the other trace elements on aflatoxin production depended on the level of trace elements present in the basal medium. In general, manganese chloride had a stimulatory effect, whereas copper sulphate depressed yields.Mycelial levels of aflatoxin had peaked and then declined before mycelial dry weights had reached maximum.High yields of aflatoxin B1 were obtained in media having a final pH as low as pH 2.8.

scholarly journals Balancing selection for aflatoxin in Aspergillus flavus is maintained through interference competition with, and fungivory by insects

2017 ◽  
Vol 284 (1869) ◽  
pp. 20172408 ◽  
Author(s):  
Milton T. Drott ◽  
Brian P. Lazzaro ◽  
Dan L. Brown ◽  
Ignazio Carbone ◽  
Michael G. Milgroom
Keyword(s):  
Aspergillus Flavus ◽  
Balancing Selection ◽  
Interference Competition ◽  
Fold Increase ◽  
Aflatoxin Production ◽  
Fitness Advantage ◽  
Naturally Occurring ◽  
Selection For ◽  
Single Larva

The role of microbial secondary metabolites in the ecology of the organisms that produce them remains poorly understood. Variation in aflatoxin production by Aspergillus flavus is maintained by balancing selection, but the ecological function and impact on fungal fitness of this compound are unknown. We hypothesize that balancing selection for aflatoxin production in A. flavus is driven by interaction with insects. To test this, we competed naturally occurring aflatoxigenic and non-aflatoxigenic fungal isolates against Drosophila larvae on medium containing 0–1750 ppb aflatoxin, using quantitative PCR to quantify A. flavus DNA as a proxy for fungal fitness. The addition of aflatoxin across this range resulted in a 26-fold increase in fungal fitness. With no added toxin, aflatoxigenic isolates caused higher mortality of Drosophila larvae and had slightly higher fitness than non-aflatoxigenic isolates. Additionally, aflatoxin production increased an average of 1.5-fold in the presence of a single larva and nearly threefold when the fungus was mechanically damaged. We argue that the role of aflatoxin in protection from fungivory is inextricably linked to its role in interference competition. Our results, to our knowledge, provide the first clear evidence of a fitness advantage conferred to A. flavus by aflatoxin when interacting with insects.

Lack of aflatoxin production by Aspergillus flavus is associated with reduced fungal growth and delayed expression of aflatoxin pathway genes

2015 ◽  
Vol 8 (3) ◽  
pp. 335-340 ◽  
Author(s):  
H. Zhang ◽  
L.L. Scharfenstein ◽  
C. Carter-Wientjes ◽  
P.-K. Chang ◽  
D. Zhang ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Animal Feed ◽  
Regulatory Gene ◽  
Fungal Growth ◽  
Aflatoxin Production ◽  
Aflatoxin Contamination ◽  
Resistance Factors ◽  
Crop Varieties ◽  
Crop Resistance ◽  
Underlying Mechanisms

Aflatoxins, produced by Aspergillus flavus and Aspergillus parasiticus, are the most toxic fungal secondary metabolites that contaminate agricultural commodities such as peanuts, cotton and maize. Understanding the underlying mechanisms of crop resistance to fungal infection is an important step for plant breeders to develop better and improved crop varieties for safe production of human food and animal feed. Infection studies have identified a resistant (R) peanut line, GT-C20, which is able to decrease aflatoxin contamination. The mycelial growth of A. flavus NRRL3357 on the R peanut line was much lower than that on the susceptible (S) peanut line, Tifrunner. Besides reducing fungal growth, the R line compared to the S line inhibited aflatoxin production completely. Real-time RT-PCR assays of both the R and S lines infected by A. flavus showed that expression of five aflatoxin biosynthetic pathway genes, the aflR regulatory gene and the aflD, aflM, aflP and aflQ structural genes, was not reduced but was significantly delayed on the R line. The results suggested that resistance factors of the R line acted negatively on A. flavus growth and also altered fungal development. The dysfunction in development changed the timing and the pattern of aflatoxin gene expression, which in part rendered A. flavus unable to produce aflatoxins.

scholarly journals Function of crzA in Fungal Development and Aflatoxin Production in Aspergillus flavus

Toxins ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 567 ◽  
Author(s):  
Su-Yeon Lim ◽  
Ye-Eun Son ◽  
Dong-Hyun Lee ◽  
Tae-Jin Eom ◽  
Min-Ju Kim ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Fungal Growth ◽  
Wall Stress ◽  
Aflatoxin Production ◽  
Colony Growth ◽  
Cell Wall Stress ◽  
Mutant Strains ◽  
Sclerotial Formation ◽  
Calcineurin Pathway

The calcineurin pathway is an important signaling cascade for growth, sexual development, stress response, and pathogenicity in fungi. In this study, we investigated the function of CrzA, a key transcription factor of the calcineurin pathway, in an aflatoxin-producing fungus Aspergillus flavus (A. flavus). To examine the role of the crzA gene, crzA deletion mutant strains in A. flavus were constructed and their phenotypes, including fungal growth, spore formation, and sclerotial formation, were examined. Absence of crzA results in decreased colony growth, the number of conidia, and sclerocia production. The crzA-deficient mutant strains were more susceptible to osmotic pressure and cell wall stress than control or complemented strains. Moreover, deletion of crzA results in a reduction in aflatoxin production. Taken together, these results demonstrate that CrzA is important for differentiation and mycotoxin production in A. flavus.

scholarly journals Detection of Aflatoxigenic and Non-Aflatoxigenic Isolates of Aspergillus flavus Isolated From Some Clinical and Environmental Sources by HPLC and PCR Techniques

2018 ◽  
Vol 12 (1) ◽  
pp. 40-48
Author(s):  
Mushtak T.S. Al-Ouqaili ◽  
Mohammed H. Muslih ◽  
Salah M. A. Al-Kubaisi
Keyword(s):  
Aspergillus Flavus ◽  
High Performance ◽  
Target Genes ◽  
High Efficiency ◽  
High Sensitivity ◽  
Aflatoxin Production ◽  
Toxin Production ◽  
Genes Encoding ◽  
Hplc Technique

This study aimed to determine the role of polymerase chain reaction (PCR) and High-performance liquid chromatography (HPLC) technique in the discrimination between aflatoxigenic and non-aflatoxigenic isolates of Aspergillus flavus. The isolates were identified based on macroscopical and microscopical characteristics, and extracted aflatoxin was detected by HPLC technique. Furthermore, DNA was extracted from the all isolates and carried out by PCR to amplify target genes encoding for toxin production (nor-1, ver-1 and aflR). The results showed that the genes (aflR, nor-1) were found in 11 (73%) of isolates, while the (ver-1) gene appeared in 10 (67%) of isolates. Both aflatoxigenic and non-aflatoxigenic isolates were also determined depending on the amplification of gene sites in the targeted DNA. HPLC technique has also used with high efficiency to ensure the aflatoxin-producing isolates and to evaluate the level of aflatoxin B1 production for 15 isolates of A. flavus. Ten isolates were able to produce aflatoxin with rates ranged from 0.78 to 45.03 ppm. PCR technique has proved high efficiency in the differentiation between aflatoxigenic and non-aflatoxigenic isolates of A. flavus. Moreover, aflatoxin production was directly associated with gene appearance and gene detection. Also, HPLC technique is a standard and superb technique in identifying and analyzing aflatoxin with high sensitivity and accuracy.

scholarly journals Genetic Responses and Aflatoxin Inhibition during Co-Culture of Aflatoxigenic and Non-Aflatoxigenic Aspergillus flavus

Toxins ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 794
Author(s):  
Rebecca R. Sweany ◽  
Brian M. Mack ◽  
Geromy G. Moore ◽  
Matthew K. Gilbert ◽  
Jeffrey W. Cary ◽  
...  
Keyword(s):  
Gene Expression ◽  
Aspergillus Flavus ◽  
Gene Clusters ◽  
Aflatoxin Production ◽  
Acid Synthesis ◽  
Aflatoxin Contamination ◽  
Oxidation Reduction ◽  
Or Gene ◽  
Genetic Responses

Aflatoxin is a carcinogenic mycotoxin produced by Aspergillus flavus. Non-aflatoxigenic (Non-tox) A. flavus isolates are deployed in corn fields as biocontrol because they substantially reduce aflatoxin contamination via direct replacement and additionally via direct contact or touch with toxigenic (Tox) isolates and secretion of inhibitory/degradative chemicals. To understand touch inhibition, HPLC analysis and RNA sequencing examined aflatoxin production and gene expression of Non-tox isolate 17 and Tox isolate 53 mono-cultures and during their interaction in co-culture. Aflatoxin production was reduced by 99.7% in 72 h co-cultures. Fewer than expected unique reads were assigned to Tox 53 during co-culture, indicating its growth and/or gene expression was inhibited in response to Non-tox 17. Predicted secreted proteins and genes involved in oxidation/reduction were enriched in Non-tox 17 and co-cultures compared to Tox 53. Five secondary metabolite (SM) gene clusters and kojic acid synthesis genes were upregulated in Non-tox 17 compared to Tox 53 and a few were further upregulated in co-cultures in response to touch. These results suggest Non-tox strains can inhibit growth and aflatoxin gene cluster expression in Tox strains through touch. Additionally, upregulation of other SM genes and redox genes during the biocontrol interaction demonstrates a potential role of inhibitory SMs and antioxidants as additional biocontrol mechanisms and deserves further exploration to improve biocontrol formulations.

scholarly journals Ssu72 Regulates Fungal Development, Aflatoxin Biosynthesis and Pathogenicity in Aspergillus flavus

Toxins ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 717
Author(s):  
Guang Yang ◽  
Xiaohong Cao ◽  
Ling Qin ◽  
Lijuan Yan ◽  
Rongsheng Hong ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Aspergillus Flavus ◽  
Pathogenic Fungus ◽  
Aflatoxin Production ◽  
Regulation Of Transcription ◽  
Aflatoxin Biosynthesis ◽  
Fungal Development ◽  
Oxidative Stresses ◽  
Novel Strategy ◽  
Phosphatase Ssu72

The RNA polymerase II (Pol II) transcription process is coordinated by the reversible phosphorylation of its largest subunit-carboxy terminal domain (CTD). Ssu72 is identified as a CTD phosphatase with specificity for phosphorylation of Ser5 and Ser7 and plays critical roles in regulation of transcription cycle in eukaryotes. However, the biofunction of Ssu72 is still unknown in Aspergillus flavus, which is a plant pathogenic fungus and produces one of the most toxic mycotoxins-aflatoxin. Here, we identified a putative phosphatase Ssu72 and investigated the function of Ssu72 in A. flavus. Deletion of ssu72 resulted in severe defects in vegetative growth, conidiation and sclerotia formation. Additionally, we found that phosphatase Ssu72 positively regulates aflatoxin production through regulating expression of aflatoxin biosynthesis cluster genes. Notably, seeds infection assays indicated that phosphatase Ssu72 is crucial for pathogenicity of A. flavus. Furthermore, the Δssu72 mutant exhibited more sensitivity to osmotic and oxidative stresses. Taken together, our study suggests that the putative phosphatase Ssu72 is involved in fungal development, aflatoxin production and pathogenicity in A. flavus, and may provide a novel strategy to prevent the contamination of this pathogenic fungus.

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