scholarly journals Transcriptional Regulation of Aflatoxin Biosynthesis and Conidiation in Aspergillus flavus by Wickerhamomyces anomalus WRL-076 for Reduction of Aflatoxin Contamination

Toxins ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 81 ◽  
Author(s):  
Sui Hua ◽  
Siov Sarreal ◽  
Perng-Kuang Chang ◽  
Jiujiang Yu
Keyword(s):  
Aspergillus Flavus ◽  
Molecular Mechanisms ◽  
Field Experiments ◽  
Regulatory Gene ◽  
Aflatoxin Contamination ◽  
Economic Losses ◽  
Expression Levels ◽  
Wickerhamomyces Anomalus ◽  
Cultural Medium ◽  
Major Producer

Aspergillus flavus is a ubiquitous saprophytic fungus found in soils across the world. The fungus is the major producer of aflatoxin (AF) B1, which is toxic and a potent carcinogen to humans. Aflatoxin B1 (AFB1) is often detected in agricultural crops such as corn, peanut, almond, and pistachio. It is a serious and recurrent problem and causes substantial economic losses. Wickerhamomyces anomalus WRL-076 was identified as an effective biocontrol yeast against A. flavus. In this study, the associated molecular mechanisms of biocontrol were investigated. We found that the expression levels of eight genes, aflR, aflJ, norA, omtA, omtB, pksA, vbs, and ver-1 in the aflatoxin biosynthetic pathway cluster were suppressed. The decreases ranged from several to 10,000 fold in fungal samples co-cultured with W. anomalus. Expression levels of conidiation regulatory genes brlA, abaA, and wetA as well as sclerotial regulatory gene (sclR) were all down regulated. Consistent with the decreased gene expression levels, aflatoxin concentrations in cultural medium were reduced to barely detectable. Furthermore, fungal biomass and conidial number were significantly reduced by 60% and more than 95%, respectively. The results validate the biocontrol efficacy of W. anomalus WRL-076 observed in the field experiments.

Occidiofungin is the key metabolite for antifungal activity of the endophytic bacterium Burkholderia sp. MS455 against Aspergillus flavus

2021 ◽  
Author(s):  
Jiayuan Jia ◽  
Emerald Ford ◽  
Sarah Hobbs ◽  
Sonya Baird ◽  
Shien Lu
Keyword(s):  
Antifungal Activity ◽  
Aspergillus Flavus ◽  
Safety Concern ◽  
Regulatory Gene ◽  
Genomic Analysis ◽  
Endophytic Bacterium ◽  
Aflatoxin Contamination ◽  
Plant Production ◽  
Antifungal Compound ◽  
Buffer Control

Aflatoxin is a secondary metabolite produced by Aspergillus fungi and presents a major food safety concern globally. Among the available methods for prevention and control of aflatoxin, the application of antifungal bacteria has gained favorability in recent years. An endophytic bacterium MS455, isolated from soybean, exhibited broad-spectrum antifungal activity against economically important pathogens, including Aspergillus flavus. MS455 was identified as a strain of Burkholderia based on genomic analysis. Random and site-specific mutations were employed in discovery of the genes that share high homology to the ocf gene cluster of Burkholderia contaminans strain MS14, which is responsible for production of the antifungal compound occidiofungin. RNA-seq analysis demonstrated ORF1, a homolog to the ambR1 LuxR-type regulatory gene, regulates occidiofungin biosynthesis in MS455. Additionally, a total of 284 differentially expressed genes, including 138 up-regulated, and 146 down-regulated genes, suggesting that, in addition to its role in occidiofungin production, ORF1 is involved in expression of multiple genes, especially those involved in ornibactin biosynthesis. Plate bioassays showed the growth of A. flavus was significantly inhibited by the wild-type strain MS455 as compared with the ORF1 mutant. Similarly, corn kernel assays showed that growth of A. flavus and aflatoxin production were reduced significantly by MS455 as compared with buffer control and the ORF1 mutant. Collectively, the results demonstrated that production of occidiofungin is essential for antifungal activity of the endophytic bacterium MS455. This research has provided insights to understanding antifungal mechanisms of MS455 and development of biological approaches to prevent aflatoxin contamination in plant production.

scholarly journals Quantitative Proteomic Analysis for High- and Low-Aflatoxin-Yield Aspergillus flavus Strains Isolated From Natural Environments

2021 ◽  
Vol 12 ◽  
Author(s):  
Tao Li ◽  
Zhaowei Zhang ◽  
Yu Wang ◽  
Ying Li ◽  
Jiang Zhu ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Molecular Mechanisms ◽  
Multiple Reaction Monitoring ◽  
Aflatoxin Contamination ◽  
Field Conditions ◽  
Mass Spectrometry Analysis ◽  
High Yield ◽  
Effective Control ◽  
Natural Environments ◽  
Tandem Mass

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.

scholarly journals Transcriptome Analysis Identified Coordinated Control of Key Pathways Regulating Cellular Physiology and Metabolism upon Aspergillus flavus Infection Resulting in Reduced Aflatoxin Production in Groundnut

2020 ◽  
Vol 6 (4) ◽  
pp. 370
Author(s):  
Pooja Soni ◽  
Spurthi N. Nayak ◽  
Rakesh Kumar ◽  
Manish K. Pandey ◽  
Namita Singh ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Molecular Mechanisms ◽  
Coordinated Control ◽  
Aflatoxin Production ◽  
Aflatoxin Contamination ◽  
Rna Seq ◽  
Resistant Genotype ◽  
Cellular Physiology ◽  
Global Health Issue ◽  
Key Pathways

Aflatoxin-affected groundnut or peanut presents a major global health issue to both commercial and subsistence farming. Therefore, understanding the genetic and molecular mechanisms associated with resistance to aflatoxin production during host–pathogen interactions is crucial for breeding groundnut cultivars with minimal level of aflatoxin contamination. Here, we performed gene expression profiling to better understand the mechanisms involved in reduction and prevention of aflatoxin contamination resulting from Aspergillus flavus infection in groundnut seeds. RNA sequencing (RNA-Seq) of 16 samples from different time points during infection (24 h, 48 h, 72 h and the 7th day after inoculation) in U 4-7-5 (resistant) and JL 24 (susceptible) genotypes yielded 840.5 million raw reads with an average of 52.5 million reads per sample. A total of 1779 unique differentially expressed genes (DEGs) were identified. Furthermore, comprehensive analysis revealed several pathways, such as disease resistance, hormone biosynthetic signaling, flavonoid biosynthesis, reactive oxygen species (ROS) detoxifying, cell wall metabolism and catabolizing and seed germination. We also detected several highly upregulated transcription factors, such as ARF, DBB, MYB, NAC and C2H2 in the resistant genotype in comparison to the susceptible genotype after inoculation. Moreover, RNA-Seq analysis suggested the occurrence of coordinated control of key pathways controlling cellular physiology and metabolism upon A. flavus infection, resulting in reduced aflatoxin production.

scholarly journals Distribution, Genetic Diversity and Biocontrol of Aflatoxigenic Aspergillus flavus in Serbian Maize Fields

Toxins ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 687
Author(s):  
Vanja Vlajkov ◽  
Mila Grahovac ◽  
Dragana Budakov ◽  
Marta Loc ◽  
Ivana Pajčin ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
High Performance ◽  
Critical Role ◽  
High Capacity ◽  
Aflatoxin Production ◽  
Elisa Test ◽  
Aflatoxin Contamination ◽  
Economic Losses ◽  
Enzyme Linked Immunosorbent Assay ◽  
The Republic

Maize is one of the leading export products in the Republic of Serbia. As a country where economic development depends on agriculture, maize production plays a critical role as a crop of strategic importance. Potential aflatoxin contamination of maize poses a risk to food and feed safety and tremendous economic losses. No aflatoxin contamination of maize samples harvested in 2019 and 2020 in different localities in the Republic of Serbia was detected by the Enzyme-Linked Immunosorbent Assay (ELISA) test and High-Performance Liquid Chromatography (HPLC) method. On the other hand, the Cluster Amplification Patterns (CAP) analyses of the isolated Aspergillus flavus strains from 2019 maize samples confirmed the presence of key biosynthesis genes responsible for aflatoxin production. Artificial inoculation and subsequent HPLC analysis of the inoculated maize samples confirmed the high capacity of the A. flavus strains for aflatoxin production, pointing to a high risk of contamination under favorable conditions. Prevention of aflatoxin contamination is primarily based on A. flavus control, where biocontrol agents play a significant role as sustainable disease management tools. In this study, antagonistic activity screening of the novel strains belonging to the Bacillus genus indicated superior suppression of A. flavus strains by two Bacillus strains isolated from the rhizosphere of Phaseolus vulgaris.

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 Transcriptome Sequencing Revealed an Inhibitory Mechanism of Aspergillus flavus Asexual Development and Aflatoxin Metabolism by Soy-Fermenting Non-Aflatoxigenic Aspergillus

2020 ◽  
Vol 21 (19) ◽  
pp. 6994 ◽  
Author(s):  
Kunlong Yang ◽  
Qingru Geng ◽  
Fengqin Song ◽  
Xiaona He ◽  
Tianran Hu ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Transcriptome Sequencing ◽  
Tca Cycle ◽  
Gene Clusters ◽  
Aflatoxin Contamination ◽  
Inhibitory Mechanism ◽  
Inhibitory Compounds ◽  
The Tca Cycle ◽  
Major Producer ◽  
And Control

Aflatoxins (AFs) have always been regarded as the most effective carcinogens, posing a great threat to agriculture, food safety, and human health. Aspergillus flavus is the major producer of aflatoxin contamination in crops. The prevention and control of A. flavus and aflatoxin continues to be a global problem. In this study, we demonstrated that the cell-free culture filtrate of Aspergillus oryzae and a non-aflatoxigenic A. flavus can effectively inhibit the production of AFB1 and the growth and reproduction of A. flavus, indicating that both of the non-aflatoxigenic Aspergillus strains secrete inhibitory compounds. Further transcriptome sequencing was performed to analyze the inhibitory mechanism of A. flavus treated with fermenting cultures, and the results revealed that genes involved in the AF biosynthesis pathway and other biosynthetic gene clusters were significantly downregulated, which might be caused by the reduced expression of specific regulators, such as AflS, FarB, and MtfA. The WGCNA results further revealed that genes involved in the TCA cycle and glycolysis were potentially involved in aflatoxin biosynthesis. Our comparative transcriptomics also revealed that two conidia transcriptional factors, brlA and abaA, were found to be significantly downregulated, which might lead to the downregulation of conidiation-specific genes, such as the conidial hydrophobins genes rodA and rodB. In summary, our research provides new insights for the molecular mechanism of controlling AF synthesis to control the proliferation of A. flavus and AF pollution.

Spatial and temporal population dynamics of Aspergillus flavus in commercial pistachio orchards in Arizona

2022 ◽  
Author(s):  
Connel Ching'anda ◽  
Joseph Atehnkeng ◽  
Ranajit Bandyopadhyay ◽  
Kenneth Callicott ◽  
Marc J Orbach ◽  
...  
Keyword(s):  
Population Dynamics ◽  
High Temperature ◽  
Aspergillus Flavus ◽  
Aflatoxin Contamination ◽  
Economic Losses ◽  
Tree Nut ◽  
Wide Range ◽  
Tree Canopies ◽  
Biocontrol Strain

Aspergillus flavus infects a wide range of crops, including pistachios, and subsequent aflatoxin contamination results in significant economic losses. Application of biocontrol products based on non-aflatoxigenic (atoxigenic) strains of A. flavus is one of the most effective tactics for controlling aflatoxins in crops. Both risk of aflatoxin contamination and effectiveness of biocontrol are influenced by the extent to which A. flavus spores move into pistachio tree canopies during periods of nut development. Thus, the purpose of this study was to evaluate spatial and temporal population dynamics of A. flavus, including the applied biocontrol strain AF36, in canopies of pistachio orchards in Arizona. Propagule densities of A. flavus were quantified on leaf samples collected from lower, middle, and upper canopies from spring through harvest in 2018 and 2019. Aspergillus flavus propagule densities peaked during periods of high temperature and rainfall in 2018 (up to 600 CFU/g) and 2019 (up to 23 CFU/g), which coincided with nut development and maturation. The applied biocontrol strain AF36 was detected at all canopy heights, but overall propagule densities were greater in the upper and middle canopy (mean = 70 CFU/g) compared to the lower canopy (mean = 47 CFU/g). Results suggest June to August is the period during which A. flavus inoculum increases in Arizona pistachio orchards, and to most effectively displace aflatoxin-producing fungi in tree canopies, biocontrol applications should precede this period. In addition, this study demonstrates that soil-applied biocontrol strains can successfully disperse throughout the canopies of commercial tree nut orchards.

scholarly journals Flavonoids Modulate the Accumulation of Toxins From Aspergillus flavus in Maize Kernels

2021 ◽  
Vol 12 ◽  
Author(s):  
Lina Castano-Duque ◽  
Matthew K. Gilbert ◽  
Brian M. Mack ◽  
Matthew D. Lebar ◽  
Carol H. Carter-Wientjes ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Molecular Mechanisms ◽  
Fungal Infections ◽  
Defense Responses ◽  
Aflatoxin Contamination ◽  
Resistant Line ◽  
Fungal Treatment ◽  
Susceptible Line ◽  
A Genome ◽  
Maize Kernels

Aspergillus flavus is an opportunistic fungal pathogen capable of producing aflatoxins, potent carcinogenic toxins that accumulate in maize kernels after infection. To better understand the molecular mechanisms of maize resistance to A. flavus growth and aflatoxin accumulation, we performed a high-throughput transcriptomic study in situ using maize kernels infected with A. flavus strain 3357. Three maize lines were evaluated: aflatoxin-contamination resistant line TZAR102, semi-resistant MI82, and susceptible line Va35. A modified genotype-environment association method (GEA) used to detect loci under selection via redundancy analysis (RDA) was used with the transcriptomic data to detect genes significantly influenced by maize line, fungal treatment, and duration of infection. Gene ontology enrichment analysis of genes highly expressed in infected kernels identified molecular pathways associated with defense responses to fungi and other microbes such as production of pathogenesis-related (PR) proteins and lipid bilayer formation. To further identify novel genes of interest, we incorporated genomic and phenotypic field data from a genome wide association analysis with gene expression data, allowing us to detect significantly expressed quantitative trait loci (eQTL). These results identified significant association between flavonoid biosynthetic pathway genes and infection by A. flavus. In planta fungal infections showed that the resistant line, TZAR102, has a higher fold increase of the metabolites naringenin and luteolin than the susceptible line, Va35, when comparing untreated and fungal infected plants. These results suggest flavonoids contribute to plant resistance mechanisms against aflatoxin contamination through modulation of toxin accumulation in maize kernels.

scholarly journals Updates on the Functions and Molecular Mechanisms of the Genes Involved in Aspergillus flavus Development and Biosynthesis of Aflatoxins

2021 ◽  
Vol 7 (8) ◽  
pp. 666
Author(s):  
Elisabeth Tumukunde ◽  
Rui Xie ◽  
Shihua Wang
Keyword(s):  
Secondary Metabolites ◽  
Aspergillus Flavus ◽  
Posttranslational Modifications ◽  
Molecular Mechanisms ◽  
Aflatoxin Production ◽  
Economic Losses ◽  
Effective Strategies ◽  
Non Invasive ◽  
Cotton Seeds ◽  
Opportunistic Fungal Pathogen

Aspergillus flavus (A. flavus) is a ubiquitous and opportunistic fungal pathogen that causes invasive and non-invasive aspergillosis in humans and animals. This fungus is also capable of infecting a large number of agriculture crops (e.g., peanuts, maze, cotton seeds, rice, etc.), causing economic losses and posing serious food-safety concerns when these crops are contaminated with aflatoxins, the most potent naturally occurring carcinogens. In particular, A. flavus and aflatoxins are intensely studied, and they continue to receive considerable attention due to their detrimental effects on humans, animals, and crops. Although several studies have been published focusing on the biosynthesis of the aforementioned secondary metabolites, some of the molecular mechanisms (e.g., posttranslational modifications, transcription factors, transcriptome, proteomics, metabolomics and transcriptome, etc.) involved in the fungal development and aflatoxin biosynthesis in A. flavus are still not fully understood. In this study, a review of the recently published studies on the function of the genes and the molecular mechanisms involved in development of A. flavus and the production of its secondary metabolites is presented. It is hoped that the information provided in this review will help readers to develop effective strategies to reduce A. flavus infection and aflatoxin production.

scholarly journals The Effect of Gut Bacteria on the Physiology of Red Palm Weevil, Rhynchophorus ferrugineus Olivier and Their Potential for the Control of This Pest

Insects ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 594
Author(s):  
Qian-Xia Liu ◽  
Zhi-Ping Su ◽  
Hui-Hui Liu ◽  
Sheng-Ping Lu ◽  
Bing Ma ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Management Strategies ◽  
Gut Bacteria ◽  
Economic Losses ◽  
Rhynchophorus Ferrugineus ◽  
Intestinal Immunity ◽  
Red Palm Weevil ◽  
Nutrient Metabolism ◽  
Palm Weevil

Red Palm Weevil (RPW), Rhynchophorus ferrugineus Olivier, is a notorious pest, which infests palm trees and has caused great economic losses worldwide. At present, insecticide applications are still the main way to control this pest. However, pesticide resistance has been detected in the field populations of RPW. Thus, future management strategies based on the novel association biological control need be developed. Recent studies have shown that the intestinal tract of RPW is often colonized by multiple microbial species as mammals and model insects, and gut bacteria have been found to promote the growth, development and immune activity of RPW larvae by modulating nutrient metabolism. Furthermore, two peptidoglycan recognition proteins (PGRPs), PGRP-LB and PGRP-S1, can act as the negative regulators to modulate the intestinal immunity to maintain the homeostasis of gut bacteria in RPW larvae. Here, we summarized the current knowledge on the gut bacterial composition of RPW and their impact on the physiological traits of RPW larvae. In contrast with metazoans, it is much easier to make genetic engineered microbes to produce some active molecules against pests. From this perspective, because of the profound effects of gut bacteria on host phenotypes, it is promising to dissect the molecular mechanisms behind their effect on host physiology and facilitate the development of microbial resource-based management methods for pest control.

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