Progress 10/01/12 to 09/30/15
Outputs
Target Audience:Results generated from this work will be presented at national, international and regional meetings of relevant associations, i.e., The Genetics Society of America, Gordon Research Conference, and the Food Research Institute (FRI) annual meetings. The PI interacted with industry, government regulators, academia, and consumers on food safety issues and provide accurate, useful information and expertise through FRI annual meetings and Newsletters. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Ming-yueh Wu, a PhD student in Genetics program, has been working on the project since 2012. This project conducts genetics, genomics, biochemistry, and bioinformatics research, and therefore provides a great education opportunity to training a next generation scientist. This project is also a fit of outreach science education. The different phenotypes of A. flavus mutants created in this project will be an attractive target for nearly all age groups and delight their interests in science. Students were exposed to the beauty of genetics and the most up-to-date research concepts. This project focused on velvet regulators, which are specific to fungi and conserved in most fungi. Understanding the velvet regulators inA. flavus will provide us an important basis to develop broad-spectrum anti-fungal methods. How have the results been disseminated to communities of interest?Results generated from this work were presented at national, international and regional meetings of relevant associations, i.e., The Genetics Society of America, Gordon Research Conference, and the Food Research Institute (FRI) annual meetings. The work will be submitted for publication in high-profile scientific journals. What do you plan to do during the next reporting period to accomplish the goals?Work will be continued under WIS01888. We will continue to examine the effects of the Velvet proteins and WetA on aflatoxin biogenesis on crops, we will do more phenotype characterizationin vivo. Besides, based on our recent data, WetA may act differently in A. nidulans, A. flavus, and A. fumigatus. Thus, we are planning to carry out RNA-seq of the WetA mutants ofA. flavus, and A. fumigatus, and cross analyzethe transcriptomes of all three species. Our recent data shows that WetA is a potential global transcription factor. We are working on ChIP-seq to elucidate the molecular regulatory mechanism of WetA in Aspergillus.
Impacts
What was accomplished under these goals?
Filamentous fungi have been used by humans for benefits, their metabolites and enzymes, including antibiotics, organic acids, pigments, and food additives. However, some are serious pathogens, which result in agricultural loss, environmental damage, and adverse health effects on humans and animals. Because of the importance of filamentous fungi in human daily life, molecular tools have been developed to enable scientists to understand these microorganisms. The main reproductive mode of filamentous fungi is the formation of asexual spores. In some cases, the fungal secondary metabolites are highly related to development. Aspergillus flavus, an opportunistic pathogen of plant and human, produces numerous secondary metabolites, including the most notorious aflatoxin. Among mycotoxins, aflatoxin B1 is one of the most potent carcinogens and can contaminate oil-seed crops, such as corn, cereals, sorghum, and peanuts. Due to the carcinogenicity and toxicity, aflatoxins have been regulated by the USFDA since 1965. In 2003, mycotoxins, including aflatoxin, were estimated to cause a crop loss of $932 million per year in the United States. The cost of aflatoxin regulation and testing averages $466 million per year. Besides of economic loss, aflatoxins are also a threat to life. Acute aflatoxicosis, associated with extremely high doses of aflatoxin, can lead to death in humans. Therefore, controlling both fungal dissemination and aflatoxin production is very important. Previous studies showed that fungal development and secondary metabolism are intimately associated via the activities of the novel velvet regulators. Velvet genes, including veA, velB, velC, and vosA, are highly conserved in many pathogenic fungi, and have been studied extensively in the model fungus Aspergillus nidulans. Understanding the function of these genes in A.flavus is of particular interest due to this species agricultural and health impact, in particular its production of aflatoxin. In linking development and secondary metabolism, the velvet genes are an ideal target for control strategies, as disruption of these genes can reduce the fungus ability to spread and produce toxin. Here, we investigated the roles of the velvet genes in A. flavus. Previous results show that the expression pattern of velvet regulators is similar to A. nidulans during lifecycle, which implies that velvet proteins function may be highly conserved in all Aspergilli. We generatedvosA, velB, velC, and vosBdeletion mutants inA. flavus. The deletion ofvelBcaused severely impaired (number, size and morphology) conidiation and the lack of sclerotia production. Moreover, thevelB-null mutant no longer produced AFB1. The deletion ofvosAcauses earlier conidiation and higher conidia number. Besides, thevosA-null mutant produces significantly less AFB1 comparing to WT.velB-andvosA-null mutant conidia contain less trehalose compared to wild type, suggesting that bothvelBandvosAare required for the spore viability inA. flavus.velC- andvosB-null mutants don't show disrupted spore viability, stress tolerance, growth rate, ortrehalose amount. However,velC- andvosB-null mutans form more sclerotia comparing to wild type under dark conditions, whilevosB-null mutant shows no significant difference in sclerotia formation under light conditions. Some Velvets are involved in aflatoxin biosynthesis. In submerged culture and liquid culture,veA-, velB-,andvosB -null mutants fail to produce AFB1. In comparison,velC-null mutant produces AFB1 in submerged culture, but fail to produce AFB1 in liquid culture.Other than theVelvets, we also characterize the function of two key development regulators, OsaA and WetA, inA. flavus. Deletion mutants of theosaAgene homologues inA. flavusshow aberrations in development and aflatoxin biogenesis. For that reason, we conclude that OsaA is a key regulatory factor that participates in controlling the process of development and mycotoxin biosynthesis inAspergillusspecies. WetA is an evolutionary conserved central developmental regulator in certain Ascomycetes. ThewetA-null mutant forms wet and white conidia, which have reduced viability and autolyzes in few days. ThewetA-null conidium has a smaller size, lacks of the crenulated structure, and eventually loses the spore content. Loss ofwetAleads to decreased trehalose level in conidia, which is a major conidia content and a protectant against various environmental stresses. Loss of WetA reduces the aflatoxin accumulation. To better understand the molecular regulatory mechanism of these regulators, we conducted RNA-seq toward wild type, vosA-, velB-, osaA-, and wetA-null mutants in A. nidulans, the model organism of Aspergillus species. Partial data has been deposited to NCBI GEO database. Several papers has been published on highly reputed journals. Our findings provides several new potential anti-fungal targets to eliminate the mycotoxin problem and promote biosafety in food industry. TheVelvetproteins, OsaA, and WetA are involved in either sporogenesis and/or mycotoxin production, which make them excellent potential broad-spectrum anti-fungal target. By dissecting the regulatory mechanisms of these regulators inA. flavus, we have more confidence to control both fungal dissemination and mycotoxin production in fields and diminish fungal hazards in food industry.
Publications
- Type:
Book Chapters
Status:
Published
Year Published:
2015
Citation:
Wu, M.-Y., and Yu, J.-H. (2015) Epigenetics of fungal secondary metabolism related genes. In: Biosynthesis and Molecular Genetics of Fungal Secondary Metabolites, Vol 2 Fungal Biology, Susanne Zeilinger, Juan-Francisco Mart�n, Carlos Garc�a-Estrada (Eds), Springer, New York pp. 29-42.
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Emri, T., Szarvas, V., Orosz, E., Antal, K., Park, H.S., Han, K.-H., Yu, J.-H., and Pocsi, I. (2015) Core oxidative stress response in Aspergillus nidulans. BMC Genomics. 16: 478.
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Park, H-S., Yu, Y.M., Lee, M-K., Maeng, P.J. Kim, S.C., and Yu, J.-H. (2015) Velvet-mediated repression of glucan synthesis in Aspergillus nidulans spores. Scientific Rep. 5:10199 | DOI: 10.1038/srep10199.
|
Progress 10/01/13 to 09/30/14
Outputs
Target Audience: Results generated from this work will be presented at national, international and regional meetings of relevant associations, i.e., The Genetics Society of America, Gordon Research Conference, and the Food Research Institute (FRI) annual meetings. The PI will interact with industry, government regulators, academia, and consumers on food safety issues and provide accurate, useful information and expertise through FRI annual meetings and Newsletters. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Ming-yueh Wu, a fourth year PhD student in Genetics program has been working on the project since 2012. This project conducts genetics, genomics, biochemistry, and bioinformatics research, and therefore provides a great education opportunity to training a next generation scientist. This project is also a fit of outreach science education. The different phenotypes of A. flavus mutants which are created in this project will be an attractive target for nearly all age groups and delight their interests in science. Students will be exposed to the beauty of genetics and the most up-to-date research concepts. This project focuses on velvet regulators, which are specific to fungi and conserved in most fungi. Understanding the velvet regulators in A. flavus will provide us an important basis to develop broad-spectrum anti-fungal methods. How have the results been disseminated to communities of interest? Results generated from this work will be presented at national, international and regional meetings of relevant associations, i.e., The Genetics Society of America, Gordon Research Conference, and the Food Research Institute (FRI) annual meetings. The work will be submitted for publication in high-profile scientific journals. What do you plan to do during the next reporting period to accomplish the goals? To further understand molecular functions of the Velvet protein family, OsaA, and WetA in A. flavus, we will carry out more integrated genetic, genomic and physiological studies in the future. For example, we are planning to do RNA-seq analyses of the OsaA and WetA mutants. The RNA-seq data will be analyzed to find more mycotocin- and conidiation-regulatory genes for further study.
Impacts
What was accomplished under these goals?
Filamentous fungi have been used by humans for benefits, their metabolites and enzymes, including antibiotics, organic acids, pigments, and food additives. However, some are serious pathogens, which result in agricultural loss, environmental damage, and adverse health effects on humans and animals. Because of the importance of filamentous fungi in human daily life, molecular tools have been developed to enable scientists to understand these microorganisms. The main reproductive mode of filamentous fungi is the formation of asexual spores. In some cases, the fungal secondary metabolites are highly related to development. Aspergillus flavus, an opportunistic pathogen of plant and human, produces numerous secondary metabolites, including the most notorious aflatoxin. Among mycotoxins, aflatoxin B1 is one of the most potent carcinogens and can contaminate oil-seed crops, such as corn, cereals, sorghum, and peanuts. Due to the carcinogenicity and toxicity, aflatoxins have been regulated by the USFDA since 1965. In 2003, mycotoxins, including aflatoxin, were estimated to cause a crop loss of $932 million per year in the United States. The cost of aflatoxin regulation and testing averages $466 million per year. Besides of economic loss, aflatoxins are also a threat to life. Acute aflatoxicosis, associated with extremely high doses of aflatoxin, can lead to death in humans. Therefore, controlling both fungal dissemination and aflatoxin production is very important. Previous studies showed that fungal development and secondary metabolism are intimately associated via the activities of the novel velvet regulators. Velvet genes, including veA, velB, velC, and vosA, are highly conserved in many pathogenic fungi, and have been studied extensively in the model fungus Aspergillus nidulans. Understanding the function of these genes in A. flavus is of particular interest due to this species agricultural and health impact, in particular its production of aflatoxin. In linking development and secondary metabolism, the velvet genes are an ideal target for control strategies, as disruption of these genes can reduce the fungus ability to spread and produce toxin. Here, we investigated the roles of the velvet genes in A. flavus. Previous results show that the expression pattern of velvet regulators is similar to A. nidulans during lifecycle, which implies that velvet proteins function may be highly conserved in all Aspergilli. Recently, we found a new member of velvet family, VelD, which only found in A. flavus and A. oryzae. We have generated vosA, velB, velC, and velD deletion mutants in A. flavus. The deletion of velB causes severely impaired (number, size and morphology) of conidiation and the lack of sclerotia production. Moreover, the velB deletion mutant no longer produces AFB1. The deletion of vosA causes earlier conidiation and shows 2 fold more conidia number in 4 day culture. Besides, the vosA deletion mutant produces significantly less AFB1 comparing to WT. velB and vosA deletion mutant conidia contain only ~30% of trehalose compared to wild type spores, suggesting that both may be required for the spore viability in A. flavus. According to protein structure analysis and EMSA analysis, we proved that VosA is a DNA-binding regulator. We conducted ChIP-seq of A. nidulans VosA to see the whole picture of VosA-regulatory mechanism. Based on the result, we can find more novel candidates of mycotoxin- and conidiation- regulatory genes and examine their functions in A. flavus. The ChIP-seq data is undergoing analysis. Although velD and vosA share high similarity amino acid sequence (64.0%), their phenotypes are very different. velD deletion mutant doesn't show reduced spore viability. Also, velD deletion causes more sclerotia formation under dark condition while no significant difference from WT under light condition. Besides, velD deletion mutant can no longer produce AFB1. Because velD is also found in A. oryzae, which is not able to produce AFB1, it would be interesting to elucidate the VelD function in A. oryzae. To understand more VelD function, we are generating velD-overexpression and velD-3xFLAG strains for further genetic and proteomic analysis. Through a gain-of-function screen of asexual sporulation repressors, we have identified the osaA gene (Orchestrator of Sex and Asex A) predicted to encode a WOPR domain protein in A. nidulans. The WOPR domain protein family is a newly identified DNA-binding class of proteins that are found in almost every sequenced fungal genome. Development is completely blocked in the osaA multi-copy strain showing a fluffy phenotype. Deleting the osaA gene in A. nidulans affects the developmental process. Likewise, the loss of the osaA gene in A. nidulans affects the expression pattern of key developmental regulators like brlA (asexual activator) and veA (sexual activator). Deletion mutants of the osaA gene homologues in A. flavus show aberrations in development and aflatoxin biogenesis. For that reason, we conclude that OsaA is a key regulatory factor that participates in controlling the process of development and mycotoxin biosynthesis in Aspergillus species. Besides of the Velvet proteins, the central regulators, BrlA, AbaA, and WetA, play essential roles in Aspergillus asexual development and are highly related with secondary metabolism. Comparing to BrlA and AbaA, WetA's function and regulatory mechanism are less understood. Loss of wetA leads to formation of wet-white conidia. Conidia are normal in microscopic appearance but completely autolyze within a few days in A. nidulans. The spore wall is defective and the trehalose biosynthesis is lack, which leads to reduced stress tolerance. In A. fumigatus, the absence of WetA causes delayed germ-tube formation and reduced hyphal branching, suggesting a role of WetA in the early phase of fungal growth. Besides, WetA accumulates preferentially in mature conidia and activates a set of spore-specific (class B) genes. Based on these results, we propose that WetA is a transcription factor (TF) and directly regulate gene expression. There were some WetA reports in A. nidulans, A. fumigatus, and other species, but never in A. flavus. This is the first study to elucidate the WetA function of mycotoxin production in A. flavus. We have generated wetA deletion mutant in A. flavus. A. flavus wetA deletion mutant produces wet-white conidia. Although WetA has no effect on AFB1 production, the loss of wetA leads to reduced conidia viability and conidia autolysis in 3 days after inoculation. Loss of wetA also results in increased beta-(1,3)-glucan level in conidia, while trehalose amount is reduced. Interestingly, A. fumigatus wetA null mutant shows delayed conidiation in comparison to wild type. However, A. flavus wetA null mutant shows earlier conidiation , A. nidulans wetA null mutant shows no difference from wild type, suggesting that WetA acts differently in late stage of conidiation in different Aspergillus species. The wetA null mutant shows a reduced growth rate. Deletion of wetA also alters stress tolerance. The wetA null mutant is sensitive to osmotic (KCl) and oxidative (H2O2) stress and is extremely sensitive to heat and UV stress. In A. flavus wetA null mutant, brlA and abaA accumulation dramatically increased at 12 hours after asexual induction. To sum up, the Velvet proteins, OsaA, and WetA are involved in either sporogenesis and/or mycotoxin production. Once we reveal the regulatory mechanisms of these proteins, we have more confidence to control theboth fungal dissemination and mycotoxin production in fields. This research will shed light on the regulation mechanism of fungal sporulation and toxin production and further give us new ideas of controlling both beneficial and harmful fungi in industry, medical, and agricultural fields.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
VelC positively controls sexual development in Aspergillus nidulans. PLoS ONE, 9(2): e89883. doi:10.1371/journal.pone.0089883
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Ahmed YL, Gerke J, Park H-S, Bayram �, Neumann P, et al. (2013) The Velvet Family of Fungal Regulators Contains a DNA-Binding Domain Structurally Similar to NF-?B. PLoS Biol 11(12): e1001750. doi:10.1371/journal.pbio.1001750
|
Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Results generated from this work will be presented at national, international and regional meetings of relevant associations, i.e., The Genetics Society of America, Gordon Research Conference, and the Food Research Institute (FRI) annual meetings. The PI will interact with industry, government regulators, academia, and consumers on food safety issues and provide accurate, useful information and expertise through FRI annual meetings and Newsletters. The work will be submitted for publication in high-profile scientific journals. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Ming-yueh Wu, a second year PhD student in Genetics program has been working on the project since 2012. This project conducts genetics, genomics, biochemistry, and bioinformatics research, and therefore provides a great education opportunity to training a next generation scientist. This project is also a fit of outreach science education. The different phenotypes of A. flavus mutants which are created in this project will be an attractive target for nearly all age groups and delight their interests in science. Students will be exposed to the beauty of genetics and the most up-to-date research concepts. This project focuses on velvet regulators, which are specific to fungi and conserved in most fungi. Understanding the velvet regulators in A. flavus will provide us an important basis to develop broad-spectrum anti-fungal methods. Besides, this research will shed light on the regulation mechanism of fungal sporulation and toxin production and further give us new ideas of controlling both beneficial and harmful fungi in industry, medical, and agricultural fields. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals? Based on the results, we propose that WetA is a transcription factor (TF) and directly regulate gene expression. There were some WetA reports in A. nidulans, A. fumigatus, and other species, but never in A. flavus. This is the first study to elucidate the WetA function of mycotoxin production in A. flavus. We have generated wetA deletion mutant in A. flavus. A. flavus wetA deletion mutant produces wet-white conidia and shows obvious pigmentation on culture agar plate. These phenotypes are similar to the wetA deletion mutant in A. nidulans. Further analyses are currently undergoing. To further understand the Velvet protein family and WetA function in A. flavus, we propose to carry out more integrated genetic, genomic and physiological studies in the future. The work will be submitted for publication in high-profile scientific journals.
Impacts
What was accomplished under these goals?
Filamentous fungi have been used by humans for benefits, their metabolites and enzymes, including antibiotics, organic acids, pigments, and food additives. However, some are serious pathogens, which result in agricultural loss, environmental damage, and adverse health effects on humans and animals. Because of the importance of filamentous fungi in human daily life, molecular tools have been developed to enable scientists to understand these microorganisms. The main reproductive mode of filamentous fungi is the formation of asexual spores. In some cases, the fungal secondary metabolites are highly related to development. Aspergillus flavus, an opportunistic pathogen of plant and human, produces numerous secondary metabolites, including the most notorious aflatoxin. Among mycotoxins, aflatoxin B1 is one of the most potent carcinogens and can contaminate oil-seed crops, such as corn, cereals, sorghum, and peanuts. Due to the carcinogenicity and toxicity, aflatoxins have been regulated by the USFDA since 1965. In 2003, mycotoxins, including aflatoxin, were estimated to cause a crop loss of $932 million per year in the United States. The cost of aflatoxin regulation and testing averages $466 million per year. Besides of economic loss, aflatoxins are also a threat to life. Acute aflatoxicosis, associated with extremely high doses of aflatoxin, can leads to death in humans. Therefore, controlling both fungal dissemination and aflatoxin production is very important. Previous studies showed that fungal development and secondary metabolism are intimately associated via the activities of the novel velvet regulators. Velvet genes, including veA, velB, velC, and vosA, are highly conserved in many pathogenic fungi, and have been studied extensively in the model fungus Aspergillus nidulans. Understanding the function of these genes in A. flavus is of particular interest due to this species agricultural and health impact, in particular its production of aflatoxin. In linking development and secondary metabolism the velvet genes are an ideal target for control strategies, as disruption of these genes can reduce the fungus ability to spread and produce toxin. Here we investigated the roles of the velvet genes in Aspergillus flavus. Previous results show that the expression pattern of velvet regulators is similar to A. nidulans during lifecycle, which implies that velvet proteins function may be highly conserved in all Aspergilli. Recently, we found a new member of velvet family, VosB, which only found in A. flavus and A. oryzae. We have generated vosA, velB, velC, and vosB deletion mutants in A. flavus. The deletion of velB causes severely impaired (number, size and morphology) of conidiation and the lack of sclerotia production. Moreover, the velB deletion mutant no longer produces AFB1. The deletion of vosA causes earlier conidiation and shows 2 fold more conidia number in 4 day culture. Besides, the vosA deletion mutant produces significantly less AFB1 comparing to WT. velB and vosA deletion mutant conidia contain only ~30% of trehalose compared to wild type spores, suggesting that both may be required for the spore viability in A. flavus. Although vosB and vosA share high similarity amino acid sequence (64.0%), however, their phenotypes are very different. vosB deletion mutant doesn’t show reduced spore viability. Also, vosB deletion causes more sclerotia formation under dark condition while no significant difference from WT under light condition. Besides, vosB deletion mutant can no longer produce AFB1. Because vosB is also found in A. oryzae which is not able to produce AFB1, it would be interesting to elucidate the VosB function in A. oryzae. Our findings presented above have led to two key hypotheses: 1) The Velvet proteins play important roles in sporulation and AF biosynthesis in A. flavus; 2) VosB is a putative regulator associated with sclerotia formation and AF production. Besides of the Velvet proteins, the central regulators, BrlA, AbaA, and WetA, play essential roles in Aspergillus asexual development and are highly related with secondary metabolism. Comparing to BrlA and AbaA, WetA’s function and regulatory mechanism are less understood. Loss of wetA leads to formation of wet-white conidia. Conidia are normal in microscopic appearance but completely autolyze within a few days in A. nidulans. The spore wall is defective and the trehalose biosynthesis is lack, which leads to reduced stress tolerance. In A. fumigatus, the absence of WetA causes delayed germ-tube formation and reduced hyphal branching, suggesting a role of WetA in the early phase of fungal growth. Besides, WetA accumulates preferentially in mature conidia and activates a set of spore-specific (class B) genes.
Publications
|
Progress 10/01/12 to 12/31/12
Outputs
OUTPUTS: In this project, we focus on revealing the regulatory mechanisms of sporulation and aflatoxin production in the major toxigenic fungus Aspergillus flavus. For the three month period in 2012, we investigated functions of the two velvet proteins VelB and VosA, which are key regulators of Aspergilli sporulation and secondary metabolism. Velvet regulators are conserved in most filamentous and dimorphic fungi. Based on A. nidulans and A. fumigatus velvet regulator research, we have identified these crucial regulators from A. flavus. Further expression analyses of key regulators, including abaA, brlA, velB, vosA, and veA, in A. flavus were conducted by Northern blotting during the lifecycle. These regulators show similar expression pattern during developmental process as A. nidulans. To further understand VelB and VosA function in A. flavus, we generated VelB and VosA deletion mutants by employing double-joint PCR. VelB deletion mutant shows significant reduction of conidiation capability and sclerotia formation in A. flavus, while VosA deletion mutant does not reveal differences of both phenotypes. In addition, we are working to generate VelB/VosA overexpression (multi-copy) mutants by inserting velB/vosA in the pRG3-AMA1 vector which contains the auxotroph marker pyr4 and the autonomous replicating sequence AMA1. Further phenotypic characterization and expression analyses throughout various stages of vegetative growth and post-developmental induction of A. flavus wild type and mutant strains will be carried out. This project conducts genetics, biochemical, and bioinformatic tools to facilitate the research of sporulation and aflatoxin production in A. flavus. Expected results include a thorough understanding of velvet regulators function, identification genes which are regulated by the velvet regulators, and defining the genetic networks regulating spore formation and aflatoxin production in A. flavus. PARTICIPANTS: Ming-yueh Wu, a second year PhD student Genetics, has been working on the project. This project involves conduction genetics, genomics, biochemistry, and bioinformatics research, and therefore provides a great opportunity to train a next generation scientist. TARGET AUDIENCES: Results generated from this work will be presented at national, international and regional meetings of relevant associations, i.e., The Genetics Society of America, Gordon Research Conference, and the Food Research Institute (FRI) annual meetings. The PI will interact with industry, government regulators, academia, and consumers on food safety issues and provide accurate, useful information and expertise through FRI annual meetings and Newsletters. The work will be submitted for publication in high-profile scientific journals. This project is also a fit for outreach science education. The different phenotypes of A. flavus mutants which are created in this project will be an attractive target for nearly all age groups and delight their interests in science. Students will be exposed to the beauty of genetics and the most up-to-date research concepts. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Filamentous fungi, including their metabolites and enzymes, have been used by humans for benefits, including antibiotics, organic acids, pigments, and food additives. However, some filamentous fungi are pathogens, which result in agricultural loss, environmental damage, and adverse health effects on humans and animals. Because of the importance of filamentous fungi in human daily life, molecular tools have been developed to enable scientists to understand these microorganisms. The main reproductive mode of filamentous fungi is the formation of asexual spores. In some cases, the fungal secondary metabolites are highly related to development. Aspergillus flavus, an opportunistic pathogen of plants and humans, produces numerous secondary metabolites, including the most notorious, aflatoxin. Among mycotoxins, aflatoxin B1 is one of the most potent carcinogens and can contaminate oil-seed crops, such as corn, cereals, sorghum, and peanuts. Due to the carcinogenicity and toxicity, aflatoxins have been regulated by the USFDA since 1965. In 2003, mycotoxins, including aflatoxin, were estimated to cause a crop loss of $932 million per year in the United States. The cost of aflatoxin regulation and testing averages $466 million per year. Aside from economic loss, aflatoxins are also a threat to human life. Acute aflatoxicosis, associated with extremely high doses of aflatoxin, can leads to death in humans. Therefore, controlling both fungal dissemination and aflatoxin production is very important. Previous studies showed that fungal development and secondary metabolism are intimately associated via the activities of the novel velvet regulators. Velvet genes, including veA, velB, velC, and vosA, are highly conserved in many pathogenic fungi, and have been studied extensively in the model fungus Aspergillus nidulans. Understanding the function of these genes in A. flavus is of particular interest due to this species' agricultural and health impact, in particular its production of aflatoxin. In linking development and secondary metabolism the velvet genes are an ideal target for control strategies, as disruption of these genes can reduce the fungus's ability to spread and produce toxin. Here we investigated the roles of the velvet genes in Aspergillus flavus. The results show that the expression pattern of velvet regulators is similar to A. nidulans during the lifecycle, which implies that the velvet proteins' function may be highly conserved in all Aspergilli. Further functional analysis will be done by conducting phenotype and expression studies of the VelB/VosA deletion and overexpression mutants. To understand the regulation network of VelB and VosA, we will carry out a series of genomic studies. Understanding the mechanisms governing sporulation and aflatoxin biosynthesis will provide new insights into controlling detrimental activities of this agriculturally important fungus. Furthermore, this project will provide opportunities to promote excellence in science education and rigorous training of graduate and undergraduate students in the disciplines of microbiology, genetics and genomics.
Publications
- No publications reported this period
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