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.

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 Stress-Activated Protein Kinase Pathway Functions To Support Protein Synthesis and Translational Adaptation in Response to Environmental Stress in Fission Yeast

2005 ◽  
Vol 4 (11) ◽  
pp. 1785-1793 ◽  
Author(s):  
Isabelle Dunand-Sauthier ◽  
Carol A. Walker ◽  
Jana Narasimhan ◽  
Amanda K. Pearce ◽  
Ronald C. Wek ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase ◽  
Osmotic Stress ◽  
Environmental Stress ◽  
Fission Yeast ◽  
Translation Initiation ◽  
Mitogen Activated Protein Kinase ◽  
Wild Type ◽  
Eif2α Phosphorylation ◽  
Mitogen Activated Protein

ABSTRACT The stress-activated protein kinase (SAPK) pathway plays a central role in coordinating gene expression in response to diverse environmental stress stimuli. We examined the role of this pathway in the translational response to stress in Schizosaccharomyces pombe. Exposing wild-type cells to osmotic stress (KCl) resulted in a rapid but transient reduction in protein synthesis. Protein synthesis was further reduced in mutants disrupting the SAPK pathway, including the mitogen-activated protein kinase Wis1 or the mitogen-activated protein kinase Spc1/Sty1, suggesting a role for these stress response factors in this translational control. Further polysome analyses revealed a role for Spc1 in supporting translation initiation during osmotic stress, and additionally in facilitating translational adaptation. Exposure to oxidative stress (H2O2) resulted in a striking reduction in translation initiation in wild-type cells, which was further reduced in spc1 − cells. Reduced translation initiation correlated with phosphorylation of the α subunit of eukaryotic initiation factor 2 (eIF2α) in wild-type cells. Disruption of Wis1 or Spc1 kinase or the downstream bZip transcription factors Atf1 and Pap1 resulted in a marked increase in eIF2α phosphorylation which was dependent on the eIF2α kinases Hri2 and Gcn2. These findings suggest a role for the SAPK pathway in supporting translation initiation and facilitating adaptation to environmental stress in part through reducing eIF2α phosphorylation in fission yeast.

scholarly journals NsdC and NsdD Affect Aspergillus flavus Morphogenesis and Aflatoxin Production

2012 ◽  
Vol 11 (9) ◽  
pp. 1104-1111 ◽  
Author(s):  
Jeffrey W. Cary ◽  
Pamela Y. Harris-Coward ◽  
Kenneth C. Ehrlich ◽  
Brian M. Mack ◽  
Shubha P. Kale ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Strong Association ◽  
Aflatoxin Production ◽  
Expression Data ◽  
Aflatoxin Biosynthesis ◽  
Wild Type ◽  
Content Type ◽  
Conidium Formation ◽  
In The Wild ◽  
Type Gene

ABSTRACT 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 Δ nsdC and Δ nsdD 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.

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.

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 AflSte20 Regulates Morphogenesis, Stress Response, and Aflatoxin Biosynthesis of Aspergillus flavus

Toxins ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 730 ◽  
Author(s):  
Ding Li ◽  
Ling Qin ◽  
Yinchun Wang ◽  
Qingchen Xie ◽  
Na Li ◽  
...  
Keyword(s):  
Stress Response ◽  
Aspergillus Flavus ◽  
Mapk Pathway ◽  
Mitogen Activated Protein Kinase ◽  
Functional Study ◽  
Aflatoxin Biosynthesis ◽  
Knockout Mutant ◽  
Serine Threonine Kinase ◽  
Threonine Kinase ◽  
Mitogen Activated Protein

Various signaling pathways in filamentous fungi help cells receive and respond to environmental information. Previous studies have shown that the mitogen-activated protein kinase (MAPK) pathway is phosphorylation-dependent and activated by different kinase proteins. Serine/threonine kinase plays a very important role in the MAPK pathway. In this study, we selected the serine/threonine kinase AflSte20 in Aspergillus flavus for functional study. By constructing Aflste20 knockout mutants and complemented strains, it was proven that the Aflste20 knockout mutant (ΔAflste20) showed a significant decrease in growth, sporogenesis, sclerotinogenesis, virulence, and infection compared to the WT (wild type) and complemented strain (ΔAflste20C). Further research indicated that ΔAflste20 has more sensitivity characteristics than WT and ΔAflste20C under various stimuli such as osmotic stress and other types of environmental stresses. Above all, our study showed that the mitogen-activated kinase AflSte20 plays an important role in the growth, conidia production, stress response and sclerotia formation, as well as aflatoxin biosynthesis, in A. flavus.

scholarly journals Activation and regulation of the Spc1 stress-activated protein kinase in Schizosaccharomyces pombe.

1996 ◽  
Vol 16 (6) ◽  
pp. 2870-2877 ◽  
Author(s):  
G Degols ◽  
K Shiozaki ◽  
P Russell
Keyword(s):  
Protein Kinase ◽  
Osmotic Stress ◽  
Schizosaccharomyces Pombe ◽  
Tyrosine Phosphatase ◽  
Negative Regulator ◽  
Mitogen Activated Protein Kinase ◽  
Wild Type ◽  
Expression Of Genes ◽  
In The Wild

Spc1, an osmotic-stress-stimulated mitogen-activated protein kinase (MAPK) homolog in the fission yeast Schizosaccharomyces pombe, is required for the induction of mitosis and survival in high-osmolarity conditions. Spc1, also known as Sty1, is activated by Wis1 MAPK kinase and inhibited by Pyp1 tyrosine phosphatase. Spc1 is most closely related to Saccharomyces cerevisiae Hog1 and mammalian p38 kinases. Whereas Hog1 is specifically responsive to osmotic stress, we report here that Spc1 is activated by multiple forms of stress, including high temperature and oxidative stress. In this regard Spc1 is more similar to mammalian p38. Activation of Spc1 is crucial for survival of various forms of stress. Spc1 regulates expression of genes encoding stress-related proteins such as glycerol-3-phosphate dehydrogenase (gpd1+) and trehalose-6-phosphate synthase (tps1+). Spc1 also promotes expression of pyp2+, which encodes a tyrosine phosphatase postulated as a negative regulator of Spc1. This proposal is supported by the finding that Spc1 associates with Pyp2 in vivo and that the amount of Spc1 tyrosine phosphorylation is lower in a Pyp2-overproducing strain than in the wild type. Moreover, the level of stress-stimulated gpd1+ expression is higher in delta pyp2 mutants than in the wild type. These findings demonstrate that Spc1 promotes expression of genes involved in stress survival and that of regulation may be commonly employed to modulate MAPK signal transduction pathways in eukaryotic species.

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 Carbon metabolism and transcriptional variation in response to salt stress in the genome shuffled Candida versatilis and a wild-type salt tolerant yeast strain

RSC Advances ◽  
2017 ◽  
Vol 7 (3) ◽  
pp. 1646-1653 ◽  
Author(s):  
Wei Qi ◽  
Wen-Tao Zhang ◽  
Fu-Ping Lu
Keyword(s):  
Salt Stress ◽  
Osmotic Stress ◽  
Carbon Metabolism ◽  
Molecular Mechanisms ◽  
Wild Type ◽  
Salt Tolerant ◽  
Transcriptional Variation ◽  
Adaptation Response ◽  
Mechanisms Of Adaptation ◽  
Candida Versatilis

The carbon metabolism and molecular mechanisms of adaptation response when exposed to conditions causing osmotic stress in strains of a wild-type of Candida versatilis (WT) and S3–5 were investigated.

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.

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