Progress 10/01/07 to 09/30/12
Outputs
OUTPUTS: We have completed the investigation of the regulatory mechanisms controlling sporulation and mycotoxin production in the model filamentous fungus Aspergillus nidulans and the opportunistic pathogenic fungus Aspergillus fumigatus. The multifunctional regulator VelB physically interacts with other velvet regulators and the resulting complexes govern development and secondary metabolism in the filamentous fungus Aspergillus nidulans. In 2012, we further characterized the role of VelB in governing asexual development and conidiogenesis in A. nidulans. In asexual spore formation, velB deletion strains show reduced number of conidia, and decreased and delayed mRNA accumulation of the key asexual regulatory genes brlA, abaA, and vosA. Overexpression of velB induces a two-fold increase of asexual spore production compared to wild type. Furthermore, the velB deletion mutant exhibits increased conidial germination rates in the presence of glucose, and rapid germination of conidia in the absence of external carbon sources. In vivo immuno-pull-down analyses reveal that VelB primarily interacts with VosA in both asexual and sexual spores, and VelB and VosA play an inter-dependent role in spore viability, focal trehalose biogenesis and control of conidial germination. Genetic and in vitro studies reveal that AbaA positively regulates velB and vosA mRNA expression during sporogenesis, and directly binds to the promoters of velB and vosA. In summary, we have revealed that VelB acts as a positive regulator of asexual development and regulates spore maturation, focal trehalose biogenesis and germination by interacting with VosA in A. nidulans. This work has been published in PLoS ONE 2012. In addition, we also characterized the four velvet regulators in the opportunistic human pathogen Aspergillus fumigatus. The deletion of AfuvosA, AfuveA and AfuvelB caused hyper-active asexual development (conidiation) and precocious and elevated accumulation of AfubrlA during developmental progression. Moreover, the absence of AfuvosA, AfuveA, or AfuvelB results in the abundant formation of conidiophores and highly increased AfubrlA mRNA accumulation in liquid submerged culture, suggesting that they act as repressors of conidiation. The deletion of AfuvosA or AfuvelB caused a reduction in conidial trehalose amount, long-term spore viability, conidial tolerance to oxidative and UV stresses, and accelerated and elevated conidial germination regardless of the presence or absence of an external carbon source, suggesting an interdependent role of them in many aspects of fungal biology. Genetic studies suggest that AfuAbaA activates AfuvosA and AfuvelB expression during the mid to late phase of conidiation. Finally, the AfuveA null mutation can be fully complemented by A. nidulans VeA, which can physically interact with AfuVelB and AfuLaeA in vivo. A model depicting the similar yet different roles of the velvet regulators governing conidiation and sporogenesis in A. fumigatus has been generated and presented. This work was published in Molecular and Microbiology 2012. PARTICIPANTS: HeeSoo Park, a PhD candidate at the Molecular and Environmental Toxicology Center has been working on the project. HeeSoo has made excellent progress in every aspect, particularly overcoming weaknesses in manuscript writing. He has published three manuscripts in high profile journals as the first author. HeeSoo is expected to get his PhD in May 2013. In addition, this project has provided opportunities to promote excellence in science education and training. The haploid model fungus A. nidulans has served as an effective and accessible system for teaching basic and difficult genetic concepts to a diverse range of students. At the same time, students have been exposed to the most up-to-date research results and techniques. Understanding the mechanisms of fungal sporulation, dissemination and toxin production of the genus Aspergillus has provided us with new insights into controlling both beneficial and detrimental activities of other industrially, medically, and agriculturally important fungi. TARGET AUDIENCES: Results generated from this work have been published in a number of high-profile journals and 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 has interacted with industry, government regulators, academia, and consumers on food safety issues and provided accurate, useful information and expertise through FRI annual meetings and Newsletters. PROJECT MODIFICATIONS: As stated, we initially proposed to identify a suppressor that bypasses the need for fluG (an upstream developmental activator) in asexual sporulation. However, multiple efforts to clone one of the three suppressor (sfgB, C, D) genes failed. Thus, we employed a genomic DNA library constructed in a multi-copy plasmid in Aspergillus and screened for the gene that could inhibit asexual sporulation when present in higher dose. From the study, we found four key developmental regulators VeA, VelB, VelC and VosA. In this project we have investigated functions of VelB, VosA and VelC in controlling sporulation and aflatoxin production in fungi.
Impacts
Fungi are extremely important organisms both in nature and for human beings. In nature, they are the main decomposers of organic substance and cause millions of dollars in losses in agriculture due to their potential to colonize on food and feed products (frequently associated with mycotoxin contamination). Mycotoxins are toxic secondary metabolites produced by certain fungi. These low molecular weight compounds (usually less than 1000 dalton) are naturally occurring and unavoidable. Mycotoxins can accumulate in maturing corn, cereals, soybeans, sorghum, peanuts, and other food and feed crops in the field and during transportation. Consumption of mycotoxin-contaminated food or feed causes acute or chronic toxicity to human and animals. In addition to concerns about adverse effects of direct consumption of mycotoxin-contaminated foods and feeds, there is also a public health concern about the potential consumption of animal-derived food products, such as meat, milk, or eggs, containing residues of mycotoxins or their metabolites. The most important relevant issues facing grain and livestock producers are preventing mycotoxin contamination of food and feed, and reducing the deleterious effects of mycotoxins on livestock. We have been investigating the mechanisms controlling sporulation and mycotoxin production in Aspergillus nidulans and Aspergillus fumigatus with a long-term goal of eliminating both fungal dispersion and mycotoxin contamination in fields. Our studies have revealed that fungal sporulation and toxin production is intimately associated, via bridging activities, to a new class of novel regulators called the velvet family proteins (VosA, VeA, VelB and VelC). A key and common property of these multi-functional velvet regulators is that they are DNA proteins that function as transcription factors controlling the expression of various genes associated with sporulation and AF biosynthesis. The absence of certain velvet genes results in abnormal sporulation and the lack of AF production. Importantly, these regulators are only specific to fungi and conserved in most (if not all) filamentous and dimorphic fungi, their functions are confirmed (or predicted) to be conserved in other fungi, providing the basis for using velvet as common anti-fungal targets. This project has investigated the molecular mechanisms of regulating both sporulation and AF production by these velvet regulators, focusing on VelB and VosA. Understanding the mechanisms governing sporulation and mycotoxin biosynthesis in molds will provide new insights into controlling both beneficial and detrimental activities of other industrially, medically, and agriculturally important fungi. Furthermore, this project has provided opportunities to promote excellence in science education and rigorous training of graduate and undergraduate students in the disciplines of microbiology, genetics and genomics. The work resulted in 10 high quality publications.
Publications
- Ni, M., Gao, N., Kwon, N.-J., Shin, K.-S., and Yu, J.-H. 2010. Regulation of Aspergillus conidiation. In Cellular and Molecular Biology of Filamentous Fungi, Borkovich, K.A., and Ebbole, D.J. (eds). Washington, D.C., ASM Press. pp. 559-576.
- Kwon, N-J., Park, H-S., Jung, S., Kim, S.C., and Yu, J-H. 2012. The putative guanine nucleotide exchange factor RicA mediates upstream signaling for growth and development in Aspergillus. Eukaryotic Cell 11: 1399-1412.
- Park, H-S., Ni, M., Jeong, K-C., Kim, Y-H., and Yu, J-H. 2012. The role, interaction and regulation of the velvet regulator VelB in Aspergillus nidulans, PLoS ONE 7(9): e45935. doi:10.1371/journal.pone.0045935
- Park, H-S., Bayram, O, Braus, G.H., Kim, S-C., and Yu, J-H. 2012. Characterization of the velvet regulators in Aspergillus fumigatus. Molecular Microbiology. 86: 937-953 DOI: 10.1111/mmi.12032
- Bayram, O.S., Bayram, O, Valerius, O., Park, H.-S., Irniger S., Gerke, J., Ni, M., Han, K.-H., Yu, J.-H., and Braus, G.H. 2010. LaeA control of velvet family regulatory proteins for light-dependent development and fungal cell-type specificity. PLoS GENETICS, 6(12):e1001226
- Xiao, P., Shin, K.-S., Wang, T., and Yu, J.-H. 2010. Aspergillus fumigatus flbB encodes two basic leucine zipper domain (bZIP) proteins required for proper asexual development and gliotoxin production. Eukaryotic Cell, 9: 1711-1723.
- Park, H.-S., and Yu, J.-H. 2012. Multi-Copy Genetic Screen in Aspergillus nidulans. Methods in Molecular Biology 944: 183-190. doi: 10.1007/978-1-62703-122-6_13.
- Park, H-S., and Yu, J-H. 2012. Genetic control of asexual sporulation in filamentous fungi, Current Opinion in Microbiology, 15: 669-677. doi: 10.1016/j.mib.2012.09.006 (Invited Review)
- Yu, J.-H. 2010. Regulation of Development in Aspergillus nidulans and Aspergillus fumigatus. Mycobiology, 38: 229-237. (Invited Review)
|
Progress 10/01/11 to 12/31/11
Outputs
OUTPUTS: We continue to investigate the regulatory mechanisms controlling sporulation and mycotoxin production in the model filamentous fungus Aspergillus nidulans and the opportunistic pathogenic fungus Aspergillus fumigatus. For the three month period in 2011, we continued to study key genes that play a crucial role in coordinating sporulation and toxin production. These key regulators were identified by a forward genetic screen employing a multi-copy genomic DNA library followed by reverse genetic and genomic analyses. Further characterization of the functions of these genes in 2011 revealed that they are in fact essential for normal sporulation and mycotoxin production in most aspergilli. Moreover, these regulators define a new class of fungi-specific DNA-binding transcription factors that are hypothesized to control expression of other genes associated with spore and toxin formation via directly binding to target DNA. Imporatantly, we further found that VelB plays an essential role in governing asexual spore formation, sclerotia (winterizing structure) production and aflatoxin biosynthesis in Aspergillus flavus. Moreover, these regulators are specific to fungi and conserved in most (if not all) filamentous and dimorphic fungi, providing the important basis for the suitability of velvet as broad-spectrum anti-fungal targets. This project employs recently developed genetic and molecular tools that facilitate the understanding of gene function in fungi. Expected results include better understanding the functions of these novel regulators, identification of groups of genes that are controlled by the two genes, and defining the genetic networks regulating spore formation and toxin production in molds PARTICIPANTS: HeeSoo Park, a PhD candidate in Molecular and Environmental Toxicology Center has been working on the project. This project will provide opportunities to promote excellence in science education and training. The haploid model fungus A. nidulans will serve as an effective and accessible system for teaching basic and difficult genetic concepts to a diverse range of students. At the same time, students will be exposed to the most up-to-date research results and techniques. Understanding the mechanisms of fungal sporulation, dissemination and toxin production the genus Aspergillus will provide us with new insights into controlling both beneficial and detrimental activities of other industrially, medically, and agriculturally important fungi. TARGET AUDIENCES: Results generated from this work have been 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. PROJECT MODIFICATIONS: As stated in the previous years' report, we initially proposed to identify a suppressor that bypasses the need for fluG (an upstream developmental activator) in asexual sporulation. However, multiple efforts to clone one of the three suppressor (sfgB, C, D) genes failed. Thus, we employed a genomic DNA library constructed in a multi-copy plasmid in Aspergillus and screened for the gene that can inhibit asexual sporulation when present in higher dose. From the study, we found four key developmental regulators VeA, VelB, VelC and VosA. In this project we are investigating functions of VelB and VelC in controlling sporulation and aflatoxin production in fungi.
Impacts
Fungi are of great importance to humankind as pathogens, environmental recyclers, industrial producers, and agricultural aids. Spores are the primary means of fungal reproduction, cell survival, propagation and infectivity. Fungi and their toxic metabolites (mycotoxins) have tremendous impact on agriculture, socio-economy and human health. Mycotoxin contamination of foods and feeds poses serious health hazards to animals and humans. Fungi are found in every environment and constitute major pathogenic organisms of plants. They cause extensive crop damage as a result of disease in the field and post-harvest food spoilage that is often associated with production of mycotoxins. In fact, contamination of agricultural commodities by mycotoxins is more problematic than the fungal diseases themselves. The mean annual cost of crop losses in the United States due to three major mycotoxins (aflatoxins, fumonisins, and deoxynivalenol) is estimated to be over $900 million. Currently, there are no practical ways to eliminate mycotoxin contamination in foods and feeds. A series of studies have revealed that fungal sporulation and mycotoxin production are intimately associated via activities of a new class of novel regulators called the velvet regulators (VosA, VeA, VelB and VelC). The absence of any one of these velvet genes results in abnormal sporulation and toxin production Importantly, these regulators are conserved in most (if not all) filamentous and dimorphic fungi and their functions are confirmed (or predicted) to be conserved in other fungi. In collaboration with Dr. Braus, we have been further investigating the molecular mechanisms bridging fungal development and mycotoxin production. We found that VeA-VelB and VosA-VelB can form a heterodimer, which then interacts with LaeA, a master regulator of secondary metabolism. The formation of the hetero-trimeric complex (LaeA-VeA-VelB or LaeA-VosA-VelB) in vivo is necessary for proper development and toxin production in fungi. VosA, VeA, VelB and LaeA all localize in the nucleus at certain developmental stages, suggesting that the heterotrimer(s) may function as transcriptional regulators. Resources and activities have made great contributions to achieve these outcomes. . Understanding the mechanisms governing sporulation and mycotoxin biosynthesis in molds will provide new insights into controlling both beneficial and detrimental activities of other industrially, medically, and agriculturally important fungi. 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. The work will be submitted for publication in high-profile scientific journals.
Publications
- Tao, L., and Yu, J.-H. 2011. AbaA and WetA govern distinct stages of Aspergillus fumigatus development. Microbiology-SGM, 157: 313 - 326.
- Park, H.-S., and Yu, J.-H. 2011 Multicopy genetic screen in Aspergillus nidulans. Humana Press, Springer Protocols. Edited by G. Turner and N.P. Keller.
- Szilagyi, M., Kwon, N-J., Bakti, F., M-Hamvas, M., Jambrik, K., Park, H-S., Pocsi, I., Yu, J-H., Emri, T. 2011 Extracellular proteinase formation in carbon starving Aspergillus nidulans cultures- physiological function and regulation. J. Basic Microbiol. 51: 625-634 DOI: 10.1002/jobm.201100068.
- Hegedűs, N., Leiter, E., Kovacs, B., Tomori, V., Kwon, N-J, Emri, T., Marx, F., Batta, G., Csernoch, L., Haas, H., Yu, J.-H., Pocsi, I. 2011 The small molecular mass antifungal protein of Penicillium chrysogenum - a mechanism of action oriented review. J. Basic Microbiol. 51: 561-571. (Invited Review)
- Jeong, K.-C, and Yu, J.-H. 2011 Investigation of in vivo protein interactions in Aspergillus spores. Humana Press, Springer Protocols. Edited by G. Turner and N.P. Keller.
|
Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Fungi are of great importance to humankind as pathogens, environmental recyclers, industrial producers, and agricultural aids. Spores are the primary means of fungal reproduction, cell survival, propagation and infectivity. Fungi and their toxic metabolites (mycotoxins) have tremendous impact on agriculture, socio-economy and human health. Mycotoxin contamination of foods and feeds poses serious health hazards to animals and humans. Fungi are found in every environment and constitute major pathogenic organisms of plants. They cause extensive crop damage as a result of disease in the field and post-harvest food spoilage that is often associated with production of mycotoxins. In fact, contamination of agricultural commodities by mycotoxins is more problematic than the fungal diseases themselves. The mean annual cost of crop losses in the United States due to three major mycotoxins (aflatoxins, fumonisins, and deoxynivalenol) is estimated to be over $900 million. Currently, there are no practical ways to eliminate mycotoxin contamination in foods and feeds. We have been investigating the regulatory mechanisms controlling sporulation and mycotoxin production in the model filamentous fungus Aspergillus nidulans and the opportunistic pathogenic fungus Aspergillus fumigatus. For the one year period in 2010, we continued to study key genes that play a crucial role in coordinating sporulation and toxin production. These key regulators were identified by a forward genetic screen employing a multi-copy genomic DNA library followed by reverse genetic and genomic analyses. Further characterization of the functions of these genes in 2010 revealed that they are in fact essential for normal sporulation and mycotoxin production in most aspergilli. Moreover, these regulators define a new class of fungi-specific transcription factors that are hypothesized to control expression of other genes associated with spore and toxin formation via binding to DNA. This project employs recently developed genetic and molecular tools that facilitate the understanding of gene function in fungi. Expected results include better understanding the functions of these novel regulators, identification of groups of genes that are controlled by the two genes, and defining the genetic networks regulating spore formation and toxin production in molds. Understanding the mechanisms governing sporulation and mycotoxin biosynthesis in molds will provide new insights into controlling both beneficial and detrimental activities of other industrially, medically, and agriculturally important fungi. 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. The work will be submitted for publication in high-profile scientific journals. PARTICIPANTS: HeeSoo Park, a PhD candidate in Molecular and Environmental Toxicology Center has been working on the project. This project will provide opportunities to promote excellence in science education and training. The haploid model fungus A. nidulans will serve as an effective and accessible system for teaching basic and difficult genetic concepts to a diverse range of students. At the same time, students will be exposed to the most up-to-date research results and techniques. Understanding the mechanisms of fungal sporulation, dissemination and toxin production the genus Aspergillus will provide us with new insights into controlling both beneficial and detrimental activities of other industrially, medically, and agriculturally important fungi. 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. PROJECT MODIFICATIONS: As stated in the last years' report, we initially proposed to identify a suppressor that bypasses the need for fluG (an upstream developmental activator) in asexual sporulation. However, multiple efforts to clone one of the three suppressor (sfgB, C, D) genes failed. Thus, we employed a genomic DNA library constructed in a multi-copy plasmid in Aspergillus and screened for the gene that can inhibit asexual sporulation when present in higher dose. From the study, we found four key developmental regulators VeA, VelB, VelC and VosA. In this project we are investigating functions of VelB and VelC in controlling sporulation and toxin production in fungi.
Impacts
Employing the model fungus Aspergillus nidulans, we have been investigating the mechanisms governing fungal sporulation and mycotoxin biosynthesis. A series of studies have revealed that fungal sporulation and mycotoxin production are intimately associated via activities of a new class of novel regulators called the velvet regulators (VosA, VeA, VelB and VelC). A key and common property of these multi-functional regulators is that they are DNA proteins that function as transcription factors controlling the expression of various genes associated with sporulation and mycotoxin biosynthesis. The absence of any one of these velvet genes results in abnormal sporulation and toxin production Importantly, these regulators are conserved in most (if not all) filamentous and dimorphic fungi and their functions are confirmed (or predicted) to be conserved in other fungi. In collaboration with Dr. Braus, we have been further investigating the molecular mechanisms bridging fungal development and mycotoxin production. We found that VeA-VelB and VosA-VelB can form a heterodimer, which then interacts with LaeA, a master regulator of secondary metabolism. The formation of the hetero-trimeric complex (LaeA-VeA-VelB or LaeA-VosA-VelB) in vivo is necessary for proper development and toxin production in fungi. VosA, VeA, VelB and LaeA all localize in the nucleus at certain developmental stages, suggesting that the heterotrimer(s) may function as transcriptional regulators. Resources and activities have made great contributions to achieve these outcomes.
Publications
- Bayram, Ö.S., Bayram, Ö, Valerius, O., Park, H.-S., Irniger S., Gerke, J., Ni, M., Han, K.-H., Yu, J.-H., and Braus, G.H. 2010. LaeA control of velvet family regulatory proteins for light-dependent development and fungal cell-type specificity. PLoS GENETICS, 6(12):e1001226.
|
Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Fungi are found in every environment and constitute major pathogenic organisms of plants. They cause extensive crop damage as a result of disease in the field and post-harvest food spoilage that is often associated with production of mycotoxins. In fact, contamination of agricultural commodities by mycotoxins is more problematic than the fungal diseases themselves. The economic costs of mycotoxins are impossible to accurately measure, but the mean annual cost of crop losses in the United States due to three major mycotoxins (aflatoxins, fumonisins, and deoxynivalenol) is estimated to be over $900 million. Currently, there are no practical ways to eliminate mycotoxin contamination in foods and feeds. We have been investigating the regulatory mechanisms controlling sporulation and toxin production in the model filamentous fungus Aspergillus nidulans and the opportunistic pathogenic fungus Aspergillus fumigatus. For the one year period in 2009, we continued to study key genes that play a crucial role in coordinating asexual and sexual sporulation and toxin production in Aspergillus. These key regulators were identified by a forward genetic screen employing a multi-copy genomic DNA library followed by reverse genetic and genomic analyses. Further characterization of the functions of these genes in 2009 revealed that they are in fact essential for normal sporulation and mycotoxin production in two aspergilli. Moreover, these regulators define a new class of fungi-specific transcription factors that are hypothesized to control expression of other genes associated with spore and toxin formation via binding to DNA. This project employs recently developed genetic and molecular tools that facilitate the understanding of gene function in fungi. Expected results include better understanding the functions of these novel regulators, identification of groups of genes that are controlled by the two genes, and defining the genetic networks regulating spore formation and toxin production in molds. Understanding the mechanisms governing sporulation and secondary metabolism in molds will provide new insights into controlling both beneficial and detrimental activities of other industrially, medically, and agriculturally important fungi. 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. As a faculty member of UW-Madison's Food Research Institute (FRI), the PI actively participates in presentation, discussion and new project development. The PI also offers expert technical advice to government, industry, and various supporting agencies. Results generated from this work will be presented at national, international and regional meetings of relevant associations. 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. PARTICIPANTS: HeeSoo Park, a PhD candidate in Molecular and Environmental Toxicology Center. This project will provide opportunities to promote excellence in science education and training. The haploid model fungus A. nidulans will serve as an effective and accessible system for teaching basic and difficult genetic concepts to a diverse range of students. At the same time, students will be exposed to the most up-to-date research results and techniques. Understanding the mechanisms of fungal sporulation, dissemination and toxin production the genus Aspergillus will provide us with new insights into controlling both beneficial and detrimental activities of other industrially, medically, and agriculturally important fungi. 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. PROJECT MODIFICATIONS: As stated in the last years report, we initially proposed to identify a suppressor that bypasses the need for fluG (an upstream developmental activator) in asexual sporulation. However, multiple efforts to clone one of the three suppressor (sfgB, C, D) genes failed. Thus, we employed a genomic DNA library constructed in a multi-copy plasmid in Aspergillus and screened for the gene that can inhibit asexual sporulation when present in higher dose. From the study, we found four key developmental regulators VeA, VelB, VelC and VosA. In this project we are investigating functions of VelB and VelC in controlling sporulation and toxin production in fungi.
Impacts
Employing the model fungus Aspergillus nidulans, we have been investigating the mechanisms governing fungal sporulation and mycotoxin biosynthesis. A series of studies have revealed that fungal sporulation and mycotoxin production are intimately associated via activities of a new class of novel regulators called the velvet proteins (VosA, VeA, VelB and VelC). A key and common property of these multi-functional regulators is that they have the DNA binding ability and function as transcription factors controlling the expression of various genes associated with sporulation and mycotoxin biosynthesis. The absence of any one of these velvet proteins results in abnormal sporulation and toxin production. Importantly, these regulators are conserved in most (if not all) filamentous and dimorphic fungi and their functions are confirmed (or predicted) to be conserved in other fungi. In collaboration with Drs. Keller and Braus, we began to understand the molecular mechanisms bridging fungal development and mycotoxin production. We found that VeA-VelB and VosA-VelB can form a heterodimer, which then interacts with LaeA, a master regulator of secondary metabolism. The formation of the hetero-trimeric complex (LaeA-VeA-VelB or LaeA-VosA-VelB) in vivo is necessary for proper development and toxin production in fungi. VosA, VeA, VelB and LaeA all localize in the nucleus at certain developmental stages, suggesting that the heterotrimer(s) may function as transcriptional regulators. Resources and activities have made great contributions to achieve these outcomes.
Publications
- Shin, K.-S., Kwon, N.-J., Park, W.-S., Kwon, G.-S., and Yu, J.-H. 2009. Differential roles of the ChiB chitinase in autolysis and cell death of Aspergillus nidulans. Eukaryot. Cell, 8:738-746.
- Pocsi, I., Leiter, E., Kwon, N.-J., Shin, K.-S., Kwon, G.-S., Pusztahelyi, T., Emri, T., Abuknesha, R., Price, R., and Yu, J.-H. 2009. Asexual sporulation signaling regulates autolysis of Aspergillus nidulans via modulating the chitinase ChiB production. J. Appl. Microbiol., 107:514-523 doi:10.1111/j.1365-2672.2009.04237.x
|
Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Fungi are found in every environment and constitute major pathogenic organisms of plants. They cause extensive crop damage as a result of disease in the field and post-harvest food spoilage that is often accompanied by production of mycotoxins. In reality, contamination of agricultural commodities by mycotoxins is more problematic than the fungal diseases themselves. The economic costs of mycotoxins are impossible to accurately measure, but the mean annual cost of crop losses in the United States due to three major mycotoxins (aflatoxins, fumonisins, and deoxynivalenol) is estimated to be over $900 million. Currently, there are no practical ways to eliminate mycotoxin contamination in foods and feeds. We have been dissecting the mechanisms controlling sporulation and toxin production in the model filamentous fungus Aspergillus nidulans and the opportunistic pathogenic fungus Aspergillus fumigatus. In 2008, we identified have been studying two genes that may play a crucial role in coordinating asexual and sexual reproduction and toxin production in Aspergillus. This was accomplished via a forward genetic screen employing a multi-copy genomic DNA library followed by reverse genetic and genomic analyses. Further characterization of the functions of these genes is in progress. 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. PARTICIPANTS: Na Gao, a PhD candidate in Molecular and Environmental Toxicology Center. HeeSoo Park, a PhD candidate in Molecular and Environmental Toxicology Center. This project will provide opportunities to promote excellence in science education and training. The haploid model fungus A. nidulans will serve as an effective and accessible system for teaching basic and difficult genetic concepts to a diverse range of students. At the same time, students will be exposed to the most up-to-date research results and techniques. Understanding the mechanisms of fungal sporulation, dissemination and toxin production the genus Aspergillus will provide us with new insights into controlling both beneficial and detrimental activities of other industrially, medically, and agriculturally important fungi. 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 Food Research Institute annual meetings and Newsletters. The work will be submitted for publication in high-profile scientific journals. PROJECT MODIFICATIONS: Initially we proposed to identify a suppressor that bypasses the need for fluG (an upstream developmental activator) in asexual sporulation. However, multiple efforts to clone one of the three suppressor (sfgB, C, D) genes failed. Thus, we employed a genomic DNA library constructed in a multi-copy plasmid in Aspergillus and screened for the gene that can inhibit asexual sporulation when present in higher dose. From the study, we found four key developmental regulators VeA, VelB, VelC and VosA. In this project we are investigating functions of VelB and VelC in controlling sporulation and toxin production in fungi.
Impacts
Employing the model fungus Aspergillus nidulans, we have been investigating the mechanisms governing fungal sporulation and mycotoxin biosynthesis. A series of studies have revealed that fungal sporulation and mycotoxin production are intimately associated via activities of a new class of novel regulators called the velvet proteins (VosA, VeA and VelB). A key and common property of these multi-functional regulators is that they have the DNA binding capacity and may function as transcription factors controlling the expression of various genes associated with sporulation and toxigenesis. The absence of any one of these velvet proteins results in abnormal sporulation and toxin production Importantly, these regulators are conserved in most (if not all) filamentous and dimorphic fungi and their functions are confirmed (or predicted) to be conserved in other fungi. In collaboration with Drs. Keller and Braus, we began to understand the molecular mechanisms bridging fungal development and mycotoxin production. We found that VeA-VelB and VosA-VelB can form a heterodimer, which then interacts with LaeA, a master regulator of secondary metabolism. The formation of the hetero-trimeric complex (LaeA-VeA-VelB or LaeA-VosA-VelB) in vivo is necessary for proper development and toxin production in fungi. VosA, VeA, VelB and LaeA all localize in the nucleus at certain developmental stages, suggesting that the heterotrimer(s) may function as transcriptional regulators. Resources and activities have made great contributions to achieve these outcomes.
Publications
- Pocsi, I; Leiter, E; Kwon, N-J; Shin, K-S; Kwon, G-S; Pusztahelyi, T; Emri, T; Abuknesha, R; Price, R; Yu, J-H. 2009 Asexual sporulation signaling regulates autolysis of Aspergillus nidulans via modulating the chitinase ChiB production. J. Appl. Microbiol. In Press
- Bayram, O, Krappmann, S., Ni, M., Bok, J-W., Helmstaedt, K., Valerius, O., Braus-Stromeyer, S., Kwon, N-K., Keller, NP., Yu, J-H, and Braus, GH. 2008. The velvet complex coordinates light, fungal development and secondary metabolism. Science, 320: 1504-1506.
- Etxebeste, O., Ni, M., Garzia, A., Kwon, N.-J., Fischer, R., Yu, J.H., Espeso, E.A. and Ugalde, U. 2008. Basic-zipper-type transcription factor FlbB controls asexual development in Aspergillus nidulans. Eukaryotic Cell. 7: 38-48.
|
Progress 10/01/07 to 12/31/07
Outputs
OUTPUTS: Fungal spores are the primary means of infecting host organisms for many human and plant pathogenic fungi. Moreover, the aerosolized fungal spores can contain potent allergens to which certain people respond with strong hypersensitive (allergic) reactions. These allergenic fungal spores are particularly problematic for farmers. In fact, there is a disease called Farmer's Lung. Even worse, many fungi are toxigenic and they produce toxic secondary metabolites called mycotoxins. Certainly, fungal spores and associated mycotoxins are trouble-causing agents that raise a number of health and food safety issues in agriculture and its associated industries. As plant pathogens, fungi cause extensive crop damage that is often accompanied by production of mycotoxins. Mycotoxins can enter our food chain by either direct contamination resulting from the use of food components contaminated with mycotoxins or indirect contamination caused by the growth of toxigenic fungi on foods and
feeds. In addition to concerns over adverse effects of mycotoxins on food and animals consuming mycotoxin-contaminated feeds, there is also public health concern over the potential for humans to consume animal-derived food products. These ingested mycotoxins can lead to deterioration of liver or kidney function and can cause cancer and even death. Given Wisconsin's prominent agricultural base, fungi (molds), fungal spores and mycotoxins constitute imperative issues to the state's human health, environmental quality and food safety. Studies showed that a significant proportion of the farm population in Wisconsin does have precipitins to the microorganisms associated with farmer's lung disease. With regard to the mycotoxin problems, in 1988 severe drought caused Wisconsin corn to become contaminated with aflatoxin. In 1992, excessive rain in the fall in Wisconsin caused more than half of the state's corn crops to be contaminated by Fusarium mycotoxins, which adversely affected livestock
in many counties. Given the importance of fungi as causal agents of human and plant disease, and broad problems caused by mycotoxins, it is critical that new approaches to control fungal infections and mycotoxin production be identified. As a part of continuing efforts, we proposed to further dissect the mechanisms controlling sporulation and toxin production in the model filamentous fungus Aspergillus nidulans. For the three-month period in 2007 (October-December), we identified a key gene that may play a crucial role in coordinating asexual and sexual reproduction and toxin production in A. nidulans. This was accomplished via a forward genetic screen employing a multi-copy genomic DNA library. Further characterization of the functions of this gene is in progress.
PARTICIPANTS: Na Gao, a PhD candidate in Molecular and Environmental Toxicology Center. This project will provide opportunities to promote excellence in science education and training. The haploid model fungus A. nidulans will serve as an effective and accessible system for teaching basic and difficult genetic concepts to a diverse range of students. At the same time, students will be exposed to the most up-to-date research results and techniques. Understanding the mechanisms of fungal reproduction and dissemination in the model Aspergillus will provide us with new insights into controlling both beneficial and detrimental activities of other industrially, medically, and agriculturally important aspergilli.
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.
PROJECT MODIFICATIONS: Initially we proposed to identify a suppressor that bypasses the need for fluG (an upstream developmental activator) in asexual sporulation. However, multiple efforts for cloning one of the three suppressor (sfgB) genes failed to identify the gene. Thus, we employed a genomic DNA library constructed in a multi-copy plasmid in Aspergillus and screened for the gene that can inhibit asexual sporulation when present in higher dose. It was expected that multi-copy repressors of sporulation would elucidate new regulatory genes that cannot be defined via chemical mutagenesis. In fact, the gene identified by this way turned out to play a crucial role in controlling sporulation and toxin production in fungi. This gene will be further studied.
Impacts
This project identifies and examines functions of one or more key genes involved in fungal spore formation and mycotoxin production. Thus, outcomes of the project will advance broad base of knowledge on fundamental fungal biology and will provide new insights into controlling fungal disease, infestation and mycotoxin contamination in foods and feeds.
Publications
- No publications reported this period
|
|