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Frontiers in Cellular and Infection... 2018Reversible protein phosphorylation is known to play important roles in the regulation of various cellular processes in eukaryotes. Phosphatase-mediated dephosphorylation...
Reversible protein phosphorylation is known to play important roles in the regulation of various cellular processes in eukaryotes. Phosphatase-mediated dephosphorylation are integral components of cellular signal pathways by counteracting the phosphorylation action of kinases. In this study, we characterized the functions of CDC14, a dual-specificity phosphatase in the development, secondary metabolism and crop infection of . Deletion of resulted in a growth defect and abnormal conidium morphology. Inactivation of caused defective septum and failure to generate sclerotia. Additionally, the deletion mutant (Δ) displayed increased sensitivity to osmotic and cell wall integrity stresses. Importantly, it had a significant increase in aflatoxin production, which was consistent with the up-regulation of the expression levels of aflatoxin biosynthesis related genes in Δ mutant. Furthermore, seeds infection assays suggested that was crucial for virulence of . It was also found that the activity of amylase was decreased in Δ mutant. AflCDC14-eRFP mainly localized to the cytoplasm and vesicles during coidial germination and mycelial development stages. Taken together, these results not only reveal the importance of the CDC14 phosphatase in the regulation of development, aflatoxin biosynthesis and virulence in , but may also provide a potential target for controlling crop infections of this fungal pathogen.
Topics: Aflatoxins; Animals; Aspergillus flavus; Cell Wall; Fungal Proteins; Gene Deletion; Humans; Osmotic Pressure; Phosphorylation; Protein Tyrosine Phosphatases; Spores, Fungal; Virulence
PubMed: 29868497
DOI: 10.3389/fcimb.2018.00141 -
Toxins Oct 2017Homeobox proteins, a class of well conserved transcription factors, regulate the expression of targeted genes, especially those involved in development. In filamentous...
Homeobox proteins, a class of well conserved transcription factors, regulate the expression of targeted genes, especially those involved in development. In filamentous fungi, homeobox genes are required for normal conidiogenesis and fruiting body formation. In the present study, we identified eight homeobox () genes in the aflatoxin-producing ascomycete, , and determined their respective role in growth, conidiation and sclerotial production. Disruption of seven of the eight genes had little to no effect on fungal growth and development. However, disruption of the homeobox gene AFLA_069100, designated as , in two morphologically different strains, CA14 and AF70, resulted in complete loss of production of conidia and sclerotia as well as aflatoxins B₁ and B₂, cyclopiazonic acid and aflatrem. Microscopic examination showed that the Δ mutants did not produce conidiophores. The inability of Δ mutants to produce conidia was related to downregulation of (bristle) and (abacus), regulatory genes for conidiophore development. These mutants also had significant downregulation of the aflatoxin pathway biosynthetic genes , , and the cluster-specific regulatory gene, . Our results demonstrate that not only plays a significant role in controlling development but is also critical for the production of secondary metabolites, such as aflatoxins.
Topics: Aflatoxins; Aspergillus flavus; DNA, Fungal; Fungal Proteins; Gene Expression Regulation, Fungal; Genes, Homeobox; Indoles; Phylogeny; Secondary Metabolism; Spores, Fungal
PubMed: 29023405
DOI: 10.3390/toxins9100315 -
Functional Genomic Analysis of Aspergillus flavus Interacting with Resistant and Susceptible Peanut.Toxins Feb 2016In the Aspergillus flavus (A. flavus)-peanut pathosystem, development and metabolism of the fungus directly influence aflatoxin contamination. To comprehensively...
In the Aspergillus flavus (A. flavus)-peanut pathosystem, development and metabolism of the fungus directly influence aflatoxin contamination. To comprehensively understand the molecular mechanism of A. flavus interaction with peanut, RNA-seq was used for global transcriptome profiling of A. flavus during interaction with resistant and susceptible peanut genotypes. In total, 67.46 Gb of high-quality bases were generated for A. flavus-resistant (af_R) and -susceptible peanut (af_S) at one (T1), three (T2) and seven (T3) days post-inoculation. The uniquely mapped reads to A. flavus reference genome in the libraries of af_R and af_S at T2 and T3 were subjected to further analysis, with more than 72% of all obtained genes expressed in the eight libraries. Comparison of expression levels both af_R vs. af_S and T2 vs. T3 uncovered 1926 differentially expressed genes (DEGs). DEGs associated with mycelial growth, conidial development and aflatoxin biosynthesis were up-regulated in af_S compared with af_R, implying that A. flavus mycelia more easily penetrate and produce much more aflatoxin in susceptible than in resistant peanut. Our results serve as a foundation for understanding the molecular mechanisms of aflatoxin production differences between A. flavus-R and -S peanut, and offer new clues to manage aflatoxin contamination in crops.
Topics: Arachis; Aspergillus flavus; Gene Expression Regulation, Fungal; Genome, Fungal; Genomics; Host-Pathogen Interactions; RNA, Fungal; Seeds; Sequence Analysis, RNA
PubMed: 26891328
DOI: 10.3390/toxins8020046 -
Scientific Reports Dec 2016Contamination of crops with aflatoxin is a serious global threat to food safety. Aflatoxin production by Aspergillus flavus is exacerbated by drought stress in the field...
Contamination of crops with aflatoxin is a serious global threat to food safety. Aflatoxin production by Aspergillus flavus is exacerbated by drought stress in the field and by oxidative stress in vitro. We examined transcriptomes of three toxigenic and three atoxigenic isolates of A. flavus in aflatoxin conducive and non-conducive media with varying levels of HO to investigate the relationship of secondary metabolite production, carbon source, and oxidative stress. We found that toxigenic and atoxigenic isolates employ distinct mechanisms to remediate oxidative damage, and that carbon source affected the isolates' expression profiles. Iron metabolism, monooxygenases, and secondary metabolism appeared to participate in isolate oxidative responses. The results suggest that aflatoxin and aflatrem biosynthesis may remediate oxidative stress by consuming excess oxygen and that kojic acid production may limit iron-mediated, non-enzymatic generation of reactive oxygen species. Together, secondary metabolite production may enhance A. flavus stress tolerance, and may be reduced by enhancing host plant tissue antioxidant capacity though genetic improvement by breeding selection.
Topics: Aspergillus flavus; Carbon; Fungal Proteins; Gene Expression Regulation, Fungal; Hydrogen Peroxide; Oxidative Stress; Transcriptome
PubMed: 27941917
DOI: 10.1038/srep38747 -
Eukaryotic Cell Sep 2012The transcription factors NsdC and NsdD are required for sexual development in Aspergillus nidulans. We now show these proteins also play a role in asexual development...
The transcription factors NsdC and NsdD are required for sexual development in Aspergillus nidulans. We now show these proteins also play a role in asexual development in the agriculturally important aflatoxin (AF)-producing fungus Aspergillus flavus. We found that both NsdC and NsdD are required for production of asexual sclerotia, normal aflatoxin biosynthesis, and conidiophore development. Conidiophores in nsdC and nsdD deletion mutants had shortened stipes and altered conidial heads compared to those of wild-type A. flavus. Our results suggest that NsdC and NsdD regulate transcription of genes required for early processes in conidiophore development preceding conidium formation. As the cultures aged, the ΔnsdC and ΔnsdD mutants produced a dark pigment that was not observed in the wild type. Gene expression data showed that although AflR is expressed at normal levels, a number of aflatoxin biosynthesis genes are expressed at reduced levels in both nsd mutants. Expression of aflD, aflM, and aflP was greatly reduced in nsdC mutants, and neither aflatoxin nor the proteins for these genes could be detected. Our results support previous studies showing that there is a strong association between conidiophore and sclerotium development and aflatoxin production in A. flavus.
Topics: Aflatoxins; Aspergillus flavus; DNA-Binding Proteins; Fungal Proteins; Gene Deletion; Gene Expression Regulation, Developmental; Morphogenesis; Spores, Fungal; Transcription Factors; Transcription, Genetic
PubMed: 22798394
DOI: 10.1128/EC.00069-12 -
BMC Molecular Biology Feb 2019Woronin bodies are fungal-specific organelles whose formation is derived from peroxisomes. The former are believed to be involved in the regulation of mycotoxins...
BACKGROUND
Woronin bodies are fungal-specific organelles whose formation is derived from peroxisomes. The former are believed to be involved in the regulation of mycotoxins biosynthesis, but not in their damage repair function. The hexagonal peroxisome protein (HexA or Hex1) encoded by hexA gene in Aspergillus is the main and the essential component of the Woronin body. However, little is known about HexA in Aspergillus flavus.
RESULTS
In this study, hexA knock-out mutant (ΔhexA) and complementation strain (ΔhexA) were produced using homologous recombination. The results showed that, ΔhexA and ΔhexA were successfully constructed. And the data analysis indicated that the colony diameter, stress sensitivity and the sclerotia formation of A. flavus were nearly not affected by the absence of HexA. Yet, the deletion of hexA gene reduced the production of asexual spores and lessened virulence on peanuts and maize seeds markedly. In addition, it was also found that there was a significant decrease of Aflatoxin B1 production in deletion mutant, when compared to wild type.
CONCLUSIONS
Therefore, it suggested that the hexA gene has an essential function in conidia production and secondary metabolism in A. flavus. The gene is also believed to be playing an important role in the invasion of A. flavus to the host.
Topics: Aflatoxin B1; Arachis; Aspergillus flavus; Fungal Proteins; Gene Deletion; Gene Knockout Techniques; Secondary Metabolism; Seeds; Spores, Fungal; Virulence; Zea mays
PubMed: 30744561
DOI: 10.1186/s12867-019-0121-3 -
Plant Disease Jul 2022Dried red chili ( spp.), a widely produced and consumed spice in Nigeria, is often contaminated by aflatoxins. Aflatoxins are potent mycotoxins of severe health and...
Dried red chili ( spp.), a widely produced and consumed spice in Nigeria, is often contaminated by aflatoxins. Aflatoxins are potent mycotoxins of severe health and economic concern worldwide. often contaminates crops with aflatoxins in warm regions; however, not all isolates are aflatoxin producers. Nonaflatoxigenic isolates have potential as biocontrol agents for aflatoxin mitigation. The current study examined the genetic diversity of ( = 325) associated with chilies in Nigeria and identified 123 nonaflatoxigenic isolates. The Nigerian isolates from chili were diverse at 17 microsatellite loci, with 5 to 36 alleles per locus, and included 152 haplotypes. The isolates that are active ingredients in Aflasafe, registered for aflatoxin biocontrol on maize and groundnuts in Nigeria, did not share haplotypes with the chili isolates. Of the 152 haplotypes, 65% produced aflatoxins in autoclaved maize, some of which (17%) produced >100,000 µg/kg of aflatoxins. Aflatoxins were not detected in 35% of the haplotypes. Cluster amplification pattern assay detected large deletions in the aflatoxin biosynthetic clusters of some (32%) of the nonaflatoxigenic haplotypes. Coinfection of chili with nonaflatoxigenic isolates from chilies ( = 7) and resulted in a significantly greater average reduction in total aflatoxins compared with that achieved by Aflasafe active ingredient isolates ( < 0.01). These nonaflatoxigenic isolates are a genetic resource for the development of biological control products for aflatoxin mitigation in chilies in Nigeria and should be evaluated under field conditions.
Topics: Aflatoxins; Aspergillus flavus; Genetic Variation; Haplotypes; Nigeria; Zea mays
PubMed: 35084943
DOI: 10.1094/PDIS-07-21-1464-RE -
International Journal of Molecular... Apr 2021()-mediated aflatoxin contamination in maize is a major global economic and health concern. As is an opportunistic seed pathogen, the identification of factors...
()-mediated aflatoxin contamination in maize is a major global economic and health concern. As is an opportunistic seed pathogen, the identification of factors contributing to kernel resistance will be of great importance in the development of novel mitigation strategies. Using V3-V4 bacterial rRNA sequencing and seeds of -resistant maize breeding lines TZAR102 and MI82 and a susceptible line, SC212, we investigated kernel-specific changes in bacterial endophytes during infection. A total of 81 bacterial genera belonging to 10 phyla were detected. Bacteria belonging to the phylum comprised 86-99% of the detected phyla, followed by (14%) and others (<5%) that changed with treatments and/or genotypes. Higher basal levels (without infection) of and in TZAR102 and increases in the abundance of and in MI82 following infection may suggest their role in resistance. Functional profiling of bacteria using 16S rRNA sequencing data revealed the presence of bacteria associated with the production of putative type II polyketides and sesquiterpenoids in the resistant vs. susceptible lines. Future characterization of endophytes predicted to possess antifungal/ anti-aflatoxigenic properties will aid in their development as effective biocontrol agents or microbiome markers for maize aflatoxin resistance.
Topics: Aspergillus flavus; Bacteria; Plant Diseases; Zea mays
PubMed: 33916873
DOI: 10.3390/ijms22073747 -
Toxins Nov 2022and the produced aflatoxins cause great hazards to food security and human health across all countries. The control of and aflatoxins in grains during storage is of...
and the produced aflatoxins cause great hazards to food security and human health across all countries. The control of and aflatoxins in grains during storage is of great significance to humans. In the current study, bacteria strain YM6 isolated from sea sediment was demonstrated effective in controlling by the production of anti-fungal volatiles. According to morphological characteristics and phylogenetic analysis, strain YM6 was identified as YM6 can produce abundant volatile compounds which could inhibit mycelial growth and conidial germination of . Moreover, it greatly prevented fungal infection and aflatoxin production on maize and peanuts during storage. The inhibition rate was 100%. Scanning electron microscopy further supported that the volatiles could destroy the cell structure of and prevent conidia germination on the grain surface. Gas chromatography/mass spectrometry revealed that dimethyl trisulfide (DMTS) with a relative abundance of 13% is the most abundant fraction in the volatiles from strain YM6. The minimal inhibitory concentration of DMTS to conidia is 200 µL/L (compound volume/airspace volume). Thus, we concluded that YM6 and the produced DMTS showed great inhibition to , which could be considered as effective biocontrol agents in further application.
Topics: Humans; Aspergillus flavus; Aflatoxins; Pseudomonas stutzeri; Phylogeny
PubMed: 36422962
DOI: 10.3390/toxins14110788 -
Toxins Jan 2022The inhibitory action of 20 antagonistic isolates against the aflatoxigenic isolate ITEM 9 (Af-9) and their efficacy in reducing aflatoxin formation in vitro were...
The inhibitory action of 20 antagonistic isolates against the aflatoxigenic isolate ITEM 9 (Af-9) and their efficacy in reducing aflatoxin formation in vitro were examined. Production of metabolites with inhibitory effect by the isolates was also investigated. Antagonistic effect against Af-9 was assessed by inhibition of radial growth of the colonies and by fungal interactions in dual confrontation tests. A total of 8 out of 20 isolates resulted in a significant growth inhibition of 3-day-old cultures of Af-9, ranging from 13% to 65%. A total of 14 isolates reduced significantly the aflatoxin B (AfB) content of 15-day-old Af-9 cultures; 4 were ineffective, and 2 increased AfB. Reduction of AfB content was up to 84.9% and 71.1% in 7- and 15-day-old cultures, respectively. Since the inhibition of Af-9 growth by metabolites of was not necessarily associated with inhibition of AfB production and vice versa, we investigated the mechanism of reduction of AfB content at the molecular level by examining two strains: one (T60) that reduced both growth and mycotoxin content; and the other (T44) that reduced mycotoxin content but not Af-9 growth. The expression analyses for the two regulatory genes and , and the structural genes , , and of the aflatoxin biosynthesis cluster indicated that neither strain was able to downregulate the aflatoxin synthesis, leading to the conclusion that the AfB content reduction by these strains was based on other mechanisms, such as enzyme degradation or complexation. Although further studies are envisaged to identify the metabolites involved in the biocontrol of and prevention of aflatoxin accumulation, as well as for assessment of the efficacy under controlled and field conditions, spp. qualify as promising agents and possible alternative options to other biocontrol agents already in use.
Topics: Aflatoxins; Aspergillus flavus; Biological Control Agents; Trichoderma
PubMed: 35202114
DOI: 10.3390/toxins14020086