1
|
Favilla LD, Herman TS, Goersch CDS, de Andrade RV, Felipe MSS, Bocca AL, Fernandes L. Expanding the Toolbox for Functional Genomics in Fonsecaea pedrosoi: The Use of Split-Marker and Biolistic Transformation for Inactivation of Tryptophan Synthase ( trpB) Gene. J Fungi (Basel) 2023; 9:jof9020224. [PMID: 36836338 PMCID: PMC9963410 DOI: 10.3390/jof9020224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 01/27/2023] [Accepted: 01/31/2023] [Indexed: 02/11/2023] Open
Abstract
Chromoblastomycosis (CBM) is a disease caused by several dematiaceous fungi from different genera, and Fonsecaea is the most common which has been clinically isolated. Genetic transformation methods have recently been described; however, molecular tools for the functional study of genes have been scarcely reported for those fungi. In this work, we demonstrated that gene deletion and generation of the null mutant by homologous recombination are achievable for Fonsecaea pedrosoi by the use of two approaches: use of double-joint PCR for cassette construction, followed by delivery of the split-marker by biolistic transformation. Through in silico analyses, we identified that F. pedrosoi presents the complete enzymatic apparatus required for tryptophan (trp) biosynthesis. The gene encoding a tryptophan synthase trpB -which converts chorismate to trp-was disrupted. The ΔtrpB auxotrophic mutant can grow with external trp supply, but germination, viability of conidia, and radial growth are defective compared to the wild-type and reconstituted strains. The use of 5-FAA for selection of trp- phenotypes and for counter-selection of strains carrying the trp gene was also demonstrated. The molecular tools for the functional study of genes, allied to the genetic information from genomic databases, significantly boost our understanding of the biology and pathogenicity of CBM causative agents.
Collapse
Affiliation(s)
- Luísa Dan Favilla
- Laboratory of Applied Immunology, Institute of Biology, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
- Graduate Program in Molecular Biology, Institute of Biology, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
| | - Tatiana Sobianski Herman
- Laboratory of Applied Immunology, Institute of Biology, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
- Graduate Program in Molecular Patology, Faculty of Medicine, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
| | - Camila da Silva Goersch
- Laboratory of Applied Immunology, Institute of Biology, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
- Graduate Program in Microbial Biology, Institute of Biology, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
| | - Rosangela Vieira de Andrade
- Graduate Program of Genomic Sciences and Biotechnology, Catholic University of Brasilia, Campus Asa Norte, Asa Norte, Federal District, Taguatinga 70790-160, Brazil
| | - Maria Sueli Soares Felipe
- Graduate Program of Genomic Sciences and Biotechnology, Catholic University of Brasilia, Campus Asa Norte, Asa Norte, Federal District, Taguatinga 70790-160, Brazil
| | - Anamélia Lorenzetti Bocca
- Laboratory of Applied Immunology, Institute of Biology, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
- Graduate Program in Molecular Biology, Institute of Biology, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
- Graduate Program in Molecular Patology, Faculty of Medicine, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
| | - Larissa Fernandes
- Laboratory of Applied Immunology, Institute of Biology, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
- Graduate Program in Microbial Biology, Institute of Biology, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Federal District, Brasilia 70910-900, Brazil
- Centro Metropolitano, Faculty of Ceilândia, Campus UnB Ceilândia, University of Brasília, Ceilândia Sul, Federal District, Brasilia 72220-275, Brazil
- Correspondence:
| |
Collapse
|
2
|
Putative Core Transcription Factors Affecting Virulence in Aspergillus flavus during Infection of Maize. J Fungi (Basel) 2023; 9:jof9010118. [PMID: 36675939 PMCID: PMC9861280 DOI: 10.3390/jof9010118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 12/20/2022] [Accepted: 12/23/2022] [Indexed: 01/17/2023] Open
Abstract
Aspergillus flavus is an opportunistic pathogen responsible for millions of dollars in crop losses annually and negative health impacts on crop consumers globally. A. flavus strains have the potential to produce aflatoxin and other toxic secondary metabolites, which often increase during plant colonization. To mitigate the impacts of this international issue, we employ a range of strategies to directly impact fungal physiology, growth and development, thus requiring knowledge on the underlying molecular mechanisms driving these processes. Here we utilize RNA-sequencing data that are obtained from in situ assays, whereby Zea mays kernels are inoculated with A. flavus strains, to select transcription factors putatively driving virulence-related gene networks. We demonstrate, through growth, sporulation, oxidative stress-response and aflatoxin/CPA analysis, that three A. flavus strains with knockout mutations for the putative transcription factors AFLA_089270, AFLA_112760, and AFLA_031450 demonstrate characteristics such as reduced growth capacity and decreased aflatoxin/CPA accumulation in kernels consistent with decreased fungal pathogenicity. Furthermore, AFLA_089270, also known as HacA, eliminates CPA production and impacts the fungus's capacity to respond to highly oxidative conditions, indicating an impact on plant colonization. Taken together, these data provide a sound foundation for elucidating the downstream molecular pathways potentially contributing to fungal virulence.
Collapse
|
3
|
It's All in the Genes: The Regulatory Pathways of Sexual Reproduction in Filamentous Ascomycetes. Genes (Basel) 2019; 10:genes10050330. [PMID: 31052334 PMCID: PMC6562746 DOI: 10.3390/genes10050330] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 04/17/2019] [Accepted: 04/24/2019] [Indexed: 12/23/2022] Open
Abstract
Sexual reproduction in filamentous ascomycete fungi results in the production of highly specialized sexual tissues, which arise from relatively simple, vegetative mycelia. This conversion takes place after the recognition of and response to a variety of exogenous and endogenous cues, and relies on very strictly regulated gene, protein, and metabolite pathways. This makes studying sexual development in fungi an interesting tool in which to study gene-gene, gene-protein, and protein-metabolite interactions. This review provides an overview of some of the most important genes involved in this process; from those involved in the conversion of mycelia into sexually-competent tissue, to those involved in the development of the ascomata, the asci, and ultimately, the ascospores.
Collapse
|
4
|
Mitogen-Activated Protein Kinase Cross-Talk Interaction Modulates the Production of Melanins in Aspergillus fumigatus. mBio 2019; 10:mBio.00215-19. [PMID: 30914505 PMCID: PMC6437049 DOI: 10.1128/mbio.00215-19] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Aspergillus fumigatus is the most important airborne human pathogenic fungus, causing thousands of deaths per year. Its lethality is due to late and often inaccurate diagnosis and the lack of efficient therapeutics. The failure of efficient prophylaxis and therapy is based on the ability of this pathogen to activate numerous salvage pathways that are capable of overcoming the different drug-derived stresses. A major role in the protection of A. fumigatus is played by melanins. Melanins are cell wall-associated macromolecules classified as virulence determinants. The understanding of the various signaling pathways acting in this organism can be used to elucidate the mechanism beyond melanin production and help to identify ideal drug targets. The pathogenic fungus Aspergillus fumigatus is able to adapt to extremely variable environmental conditions. The A. fumigatus genome contains four genes coding for mitogen-activated protein kinases (MAPKs), which are important regulatory knots involved in diverse cellular responses. From a clinical perspective, MAPK activity has been connected to salvage pathways, which can determine the failure of effective treatment of invasive mycoses using antifungal drugs. Here, we report the characterization of the Saccharomyces cerevisiae Fus3 ortholog in A. fumigatus, designated MpkB. We demonstrate that MpkB is important for conidiation and that its deletion induces a copious increase of dihydroxynaphthalene (DHN)-melanin production. Simultaneous deletion of mpkB and mpkA, the latter related to maintenance of the cell wall integrity, normalized DHN-melanin production. Localization studies revealed that MpkB translocates into the nuclei when A. fumigatus germlings are exposed to caspofungin stress, and this is dependent on the cross-talk interaction with MpkA. Additionally, DHN-melanin formation was also increased after deletion of genes coding for the Gα protein GpaA and for the G protein-coupled receptor GprM. Yeast two-hybrid and coimmunoprecipitation assays confirmed that GpaA and GprM interact, suggesting their role in the MpkB signaling cascade.
Collapse
|
5
|
Gilbert MK, Mack BM, Moore GG, Downey DL, Lebar MD, Joardar V, Losada L, Yu J, Nierman WC, Bhatnagar D. Whole genome comparison of Aspergillus flavus L-morphotype strain NRRL 3357 (type) and S-morphotype strain AF70. PLoS One 2018; 13:e0199169. [PMID: 29966003 PMCID: PMC6028093 DOI: 10.1371/journal.pone.0199169] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 06/01/2018] [Indexed: 01/03/2023] Open
Abstract
Aspergillus flavus is a saprophytic fungus that infects corn, peanuts, tree nuts and other agriculturally important crops. Once the crop is infected the fungus has the potential to secrete one or more mycotoxins, the most carcinogenic of which is aflatoxin. Aflatoxin contaminated crops are deemed unfit for human or animal consumption, which results in both food and economic losses. Within A. flavus, two morphotypes exist: the S strains (small sclerotia) and L strains (large sclerotia). Significant morphological and physiological differences exist between the two morphotypes. For example, the S-morphotypes produces sclerotia that are smaller (< 400 μm), greater in quantity, and contain higher concentrations of aflatoxin than the L-morphotypes (>400 μm). The morphotypes also differ in pigmentation, pH homeostasis in culture and the number of spores produced. Here we report the first full genome sequence of an A. flavus S morphotype, strain AF70. We provide a comprehensive comparison of the A. flavus S-morphotype genome sequence with a previously sequenced genome of an L-morphotype strain (NRRL 3357), including an in-depth analysis of secondary metabolic clusters and the identification SNPs within their aflatoxin gene clusters.
Collapse
Affiliation(s)
- Matthew K. Gilbert
- Food and Feed Safety Unit, USDA, New Orleans, Louisiana, United States of America
- * E-mail:
| | - Brian M. Mack
- Food and Feed Safety Unit, USDA, New Orleans, Louisiana, United States of America
| | - Geromy G. Moore
- Food and Feed Safety Unit, USDA, New Orleans, Louisiana, United States of America
| | - Darlene L. Downey
- Food and Feed Safety Unit, USDA, New Orleans, Louisiana, United States of America
| | - Matthew D. Lebar
- Food and Feed Safety Unit, USDA, New Orleans, Louisiana, United States of America
| | - Vinita Joardar
- The J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Liliana Losada
- The J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - JiuJiang Yu
- Food Quality Laboratory, USDA, Beltsville, Maryland, United States of America
| | - William C. Nierman
- The J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Deepak Bhatnagar
- Food and Feed Safety Unit, USDA, New Orleans, Louisiana, United States of America
| |
Collapse
|
6
|
Manfiolli AO, Dos Reis TF, de Assis LJ, de Castro PA, Silva LP, Hori JI, Walker LA, Munro CA, Rajendran R, Ramage G, Goldman GH. Mitogen activated protein kinases (MAPK) and protein phosphatases are involved in Aspergillus fumigatus adhesion and biofilm formation. Cell Surf 2018; 1:43-56. [PMID: 32743127 PMCID: PMC7389341 DOI: 10.1016/j.tcsw.2018.03.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 03/08/2018] [Accepted: 03/14/2018] [Indexed: 12/28/2022] Open
Abstract
The main characteristic of biofilm formation is extracellular matrix (ECM) production. The cells within the biofilm are surrounded by ECM which provides structural integrity and protection. During an infection, this protection is mainly against cells of the immune system and antifungal drugs. A. fumigatus forms biofilms during static growth on a solid substratum and in chronic aspergillosis infections. It is important to understand how, and which, A. fumigatus signal transduction pathways are important for the adhesion and biofilm formation in a host during infection. Here we investigated the role of MAP kinases and protein phosphatases in biofilm formation. The loss of the MAP kinases MpkA, MpkC and SakA had an impact on the cell surface and the ECM during biofilm formation and reduced the adherence of A. fumigatus to polystyrene and fibronectin-coated plates. The phosphatase null mutants ΔsitA and ΔptcB, involved in regulation of MpkA and SakA phosphorylation, influenced cell wall carbohydrate exposure. Moreover, we characterized the A. fumigatus protein phosphatase PphA. The ΔpphA strain was more sensitive to cell wall-damaging agents, had increased β-(1,3)-glucan and reduced chitin, decreased conidia phagocytosis by Dictyostelium discoideum and reduced adhesion and biofilm formation. Finally, ΔpphA strain was avirulent in a murine model of invasive pulmonary aspergillosis and increased the released of tumor necrosis factor alpha (TNF-α) from bone marrow derived macrophages (BMDMs). These results show that MAP kinases and phosphatases play an important role in signaling pathways that regulate the composition of the cell wall, extracellular matrix production as well as adhesion and biofilm formation in A. fumigatus.
Collapse
Affiliation(s)
- Adriana Oliveira Manfiolli
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Thaila Fernanda Dos Reis
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Leandro José de Assis
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Patrícia Alves de Castro
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Lilian Pereira Silva
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Juliana I Hori
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Louise A Walker
- School of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Carol A Munro
- School of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Ranjith Rajendran
- Infection and Immunity Research Group, Glasgow Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, The University of Glasgow, 378 Sauchiehall Street, Glasgow G2 3JZ, UK
| | - Gordon Ramage
- Infection and Immunity Research Group, Glasgow Dental School, School of Medicine, College of Medical, Veterinary and Life Sciences, The University of Glasgow, 378 Sauchiehall Street, Glasgow G2 3JZ, UK
| | - Gustavo H Goldman
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| |
Collapse
|
7
|
Choera T, Zelante T, Romani L, Keller NP. A Multifaceted Role of Tryptophan Metabolism and Indoleamine 2,3-Dioxygenase Activity in Aspergillus fumigatus-Host Interactions. Front Immunol 2018; 8:1996. [PMID: 29403477 PMCID: PMC5786828 DOI: 10.3389/fimmu.2017.01996] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 12/22/2017] [Indexed: 12/19/2022] Open
Abstract
Aspergillus fumigatus is the most prevalent filamentous fungal pathogen of humans, causing either severe allergic bronchopulmonary aspergillosis or often fatal invasive pulmonary aspergillosis (IPA) in individuals with hyper- or hypo-immune deficiencies, respectively. Disease is primarily initiated upon the inhalation of the ubiquitous airborne conidia—the initial inoculum produced by A. fumigatus—which are complete developmental units with an ability to exploit diverse environments, ranging from agricultural composts to animal lungs. Upon infection, conidia initially rely on their own metabolic processes for survival in the host’s lungs, a nutritionally limiting environment. One such nutritional limitation is the availability of aromatic amino acids (AAAs) as animals lack the enzymes to synthesize tryptophan (Trp) and phenylalanine and only produce tyrosine from dietary phenylalanine. However, A. fumigatus produces all three AAAs through the shikimate–chorismate pathway, where they play a critical role in fungal growth and development and in yielding many downstream metabolites. The downstream metabolites of Trp in A. fumigatus include the immunomodulatory kynurenine derived from indoleamine 2,3-dioxygenase (IDO) and toxins such as fumiquinazolines, gliotoxin, and fumitremorgins. Host IDO activity and/or host/microbe-derived kynurenines are increasingly correlated with many Aspergillus diseases including IPA and infections of chronic granulomatous disease patients. In this review, we will describe the potential metabolic cross talk between the host and the pathogen, specifically focusing on Trp metabolism, the implications for therapeutics, and the recent studies on the coevolution of host and microbe IDO activation in regulating inflammation, while controlling infection.
Collapse
Affiliation(s)
- Tsokyi Choera
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States
| | - Teresa Zelante
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Luigina Romani
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, United States.,Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, United States
| |
Collapse
|
8
|
Manfiolli AO, de Castro PA, dos Reis TF, Dolan S, Doyle S, Jones G, Riaño Pachón DM, Ulaş M, Noble LM, Mattern DJ, Brakhage AA, Valiante V, Silva-Rocha R, Bayram O, Goldman GH. Aspergillus fumigatusprotein phosphatase PpzA is involved in iron assimilation, secondary metabolite production, and virulence. Cell Microbiol 2017; 19. [DOI: 10.1111/cmi.12770] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 06/28/2017] [Accepted: 07/14/2017] [Indexed: 01/19/2023]
Affiliation(s)
| | - Patrícia Alves de Castro
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto; Universidade de São Paulo; Ribeirão Preto Brazil
| | - Thaila Fernanda dos Reis
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto; Universidade de São Paulo; Ribeirão Preto Brazil
| | - Stephen Dolan
- Department of Biology; Maynooth University; Maynooth Co. Kildare Ireland
| | - Sean Doyle
- Department of Biology; Maynooth University; Maynooth Co. Kildare Ireland
| | - Gary Jones
- Department of Biology; Maynooth University; Maynooth Co. Kildare Ireland
| | - Diego M. Riaño Pachón
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE); Centro Nacional de Pesquisa em Energia e Materiais (CNPEM); Campinas São Paulo Brazil
| | - Mevlüt Ulaş
- Department of Biology; Maynooth University; Maynooth Co. Kildare Ireland
| | | | - Derek J. Mattern
- Department of Molecular and Applied Microbiology; Leibniz Institute for Natural Product Research and Infection Biology-Hans Knöll Institute; Jena Germany
- University of Jena; Jena Germany
| | - Axel A. Brakhage
- Department of Molecular and Applied Microbiology; Leibniz Institute for Natural Product Research and Infection Biology-Hans Knöll Institute; Jena Germany
- University of Jena; Jena Germany
| | - Vito Valiante
- Leibniz Research Group-Biobricks of Microbial Natural Product Syntheses; Leibniz Institute for Natural Product Research and Infection Biology-Hans Knöll Institute; Jena Germany
| | - Rafael Silva-Rocha
- Faculdade de Medicina de Ribeirão Preto; Universidade de São Paulo; Ribeirão Preto Brazil
| | - Ozgur Bayram
- Department of Biology; Maynooth University; Maynooth Co. Kildare Ireland
| | - Gustavo H. Goldman
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto; Universidade de São Paulo; Ribeirão Preto Brazil
| |
Collapse
|
9
|
Zhi QQ, Li JY, Liu QY, He ZM. A cytosine methyltransferase ortholog dmtA is involved in the sensitivity of Aspergillus flavus to environmental stresses. Fungal Biol 2017; 121:501-514. [DOI: 10.1016/j.funbio.2017.02.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 01/21/2017] [Accepted: 02/01/2017] [Indexed: 01/05/2023]
|
10
|
Satterlee T, Cary JW, Calvo AM. RmtA, a Putative Arginine Methyltransferase, Regulates Secondary Metabolism and Development in Aspergillus flavus. PLoS One 2016; 11:e0155575. [PMID: 27213959 PMCID: PMC4877107 DOI: 10.1371/journal.pone.0155575] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 05/01/2016] [Indexed: 12/31/2022] Open
Abstract
Aspergillus flavus colonizes numerous oil seed crops such as corn, peanuts, treenuts and cotton worldwide, contaminating them with aflatoxin and other harmful potent toxins. In the phylogenetically related model fungus Aspergillus nidulans, the methyltransferase, RmtA, has been described to be involved in epigenetics regulation through histone modification. Epigenetics regulation affects a variety of cellular processes, including morphogenesis and secondary metabolism. Our study shows that deletion of rmtA in A. flavus results in hyperconidiating colonies, indicating that rmtA is a repressor of asexual development in this fungus. The increase in conidiation in the absence of rmtA coincides with greater expression of brlA, abaA, and wetA compared to that in the wild type. Additionally, the rmtA deletion mutant presents a drastic reduction or loss of sclerotial production, while forced expression of this gene increased the ability of this fungus to generate these resistant structures, revealing rmtA as a positive regulator of sclerotial formation. Importantly, rmtA is also required for the production of aflatoxin B1 in A. flavus, affecting the expression of aflJ. Furthermore, biosynthesis of additional metabolites is also controlled by rmtA, indicating a broad regulatory output in the control of secondary metabolism. This study also revealed that rmtA positively regulates the expression of the global regulatory gene veA, which could contribute to mediate the effects of rmtA on development and secondary metabolism in this relevant opportunistic plant pathogen.
Collapse
Affiliation(s)
- Timothy Satterlee
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, United States of America
| | - Jeffrey W. Cary
- USDA, ARS, Southern Regional Research Center, New Orleans, LA, 70124, United States of America
| | - Ana M. Calvo
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, United States of America
- * E-mail:
| |
Collapse
|
11
|
Wang PM, Choera T, Wiemann P, Pisithkul T, Amador-Noguez D, Keller NP. TrpE feedback mutants reveal roadblocks and conduits toward increasing secondary metabolism in Aspergillus fumigatus. Fungal Genet Biol 2015; 89:102-113. [PMID: 26701311 DOI: 10.1016/j.fgb.2015.12.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2015] [Revised: 11/23/2015] [Accepted: 12/05/2015] [Indexed: 12/11/2022]
Abstract
Small peptides formed from non-ribosomal peptide synthetases (NRPS) are bioactive molecules produced by many fungi including the genus Aspergillus. A subset of NRPS utilizes tryptophan and its precursor, the non-proteinogenic amino acid anthranilate, in synthesis of various metabolites such as Aspergillus fumigatus fumiquinazolines (Fqs) produced by the fmq gene cluster. The A. fumigatus genome contains two putative anthranilate synthases - a key enzyme in conversion of anthranilic acid to tryptophan - one beside the fmq cluster and one in a region of co-linearity with other Aspergillus spp. Only the gene found in the co-linear region, trpE, was involved in tryptophan biosynthesis. We found that site-specific mutations of the TrpE feedback domain resulted in significantly increased production of anthranilate, tryptophan, p-aminobenzoate and fumiquinazolines FqF and FqC. Supplementation with tryptophan restored metabolism to near wild type levels in the feedback mutants and suggested that synthesis of the tryptophan degradation product kynurenine could negatively impact Fq synthesis. The second putative anthranilate synthase gene next to the fmq cluster was termed icsA for its considerable identity to isochorismate synthases in bacteria. Although icsA had no impact on A. fumigatus Fq production, deletion and over-expression of icsA increased and decreased respectively aromatic amino acid levels suggesting that IcsA can draw from the cellular chorismate pool.
Collapse
Affiliation(s)
- Pin-Mei Wang
- Ocean College, Zhejiang University, Hangzhou 310058, Zhejiang Province, PR China
| | - Tsokyi Choera
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, USA
| | - Philipp Wiemann
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, USA
| | | | | | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, USA; Department of Bacteriology, University of Wisconsin, Madison, USA.
| |
Collapse
|
12
|
Gilbert MK, Mack BM, Wei Q, Bland JM, Bhatnagar D, Cary JW. RNA sequencing of an nsdC mutant reveals global regulation of secondary metabolic gene clusters in Aspergillus flavus. Microbiol Res 2015; 182:150-61. [PMID: 26686623 DOI: 10.1016/j.micres.2015.08.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 08/21/2015] [Accepted: 08/31/2015] [Indexed: 01/16/2023]
Abstract
The filamentous fungus, Aspergillus flavus (A. flavus) is an opportunistic pathogen capable of invading a number of crops and contaminating them with toxic secondary metabolites such as aflatoxins. Characterizing the molecular mechanisms governing growth and development of this organism is vital for developing safe and effective strategies for reducing crop contamination. The transcription factor nsdC has been identified as being required for normal asexual development and aflatoxin production in A. flavus. Building on a previous study using a large (L)-sclerotial morphotype A. flavus nsdC mutant we observed alterations in conidiophore development and loss of sclerotial and aflatoxin production using a nsdC mutant of a small (S)-sclerotial morphotype, that normally produces aflatoxin and sclerotia in quantities much higher than the L-morphotype. RNA sequencing analysis of the nsdC knockout mutant and isogenic control strain identified a number of differentially expressed genes related to development and production of secondary metabolites, including aflatoxin, penicillin and aflatrem. Further, RNA-seq data indicating down regulation of aflatrem biosynthetic gene expression in the nsdC mutant correlated with HPLC analyses showing a decrease in aflatrem levels. The current study expands the role of nsdC as a globally acting transcription factor that is a critical regulator of both asexual reproduction and secondary metabolism in A. flavus.
Collapse
Affiliation(s)
- Matthew K Gilbert
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA
| | - Brian M Mack
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA
| | - Qijian Wei
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA
| | - John M Bland
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA
| | - Deepak Bhatnagar
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA
| | - Jeffrey W Cary
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA.
| |
Collapse
|
13
|
Baidya S, Duran RM, Lohmar JM, Harris-Coward PY, Cary JW, Hong SY, Roze LV, Linz JE, Calvo AM. VeA is associated with the response to oxidative stress in the aflatoxin producer Aspergillus flavus. EUKARYOTIC CELL 2014; 13:1095-103. [PMID: 24951443 PMCID: PMC4135802 DOI: 10.1128/ec.00099-14] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 06/14/2014] [Indexed: 12/20/2022]
Abstract
Survival of fungal species depends on the ability of these organisms to respond to environmental stresses. Osmotic stress or high levels of reactive oxygen species (ROS) can cause stress in fungi resulting in growth inhibition. Both eukaryotic and prokaryotic cells have developed numerous mechanisms to counteract and survive the stress in the presence of ROS. In many fungi, the HOG signaling pathway is crucial for the oxidative stress response as well as for osmotic stress response. This study revealed that while the osmotic stress response is only slightly affected by the master regulator veA, this gene, also known to control morphological development and secondary metabolism in numerous fungal species, has a profound effect on the oxidative stress response in the aflatoxin-producing fungus Aspergillus flavus. We found that the expression of A. flavus homolog genes involved in the HOG signaling pathway is regulated by veA. Deletion of veA resulted in a reduction in transcription levels of oxidative stress response genes after exposure to hydrogen peroxide. Furthermore, analyses of the effect of VeA on the promoters of cat1 and trxB indicate that the presence of VeA alters DNA-protein complex formation. This is particularly notable in the cat1 promoter, where the absence of VeA results in abnormally stronger complex formation with reduced cat1 expression and more sensitivity to ROS in a veA deletion mutant, suggesting that VeA might prevent binding of negative transcription regulators to the cat1 promoter. Our study also revealed that veA positively influences the expression of the transcription factor gene atfB and that normal formation of DNA-protein complexes in the cat1 promoter is dependent on AtfB.
Collapse
Affiliation(s)
- Sachin Baidya
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - Rocio M Duran
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - Jessica M Lohmar
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - Pamela Y Harris-Coward
- Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, Louisiana, USA
| | - Jeffrey W Cary
- Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, Louisiana, USA
| | - Sung-Yong Hong
- Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Ludmila V Roze
- Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - John E Linz
- Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Ana M Calvo
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| |
Collapse
|
14
|
NsdC and NsdD affect Aspergillus flavus morphogenesis and aflatoxin production. EUKARYOTIC CELL 2012; 11:1104-11. [PMID: 22798394 DOI: 10.1128/ec.00069-12] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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 ΔnsdC and ΔnsdD mutants produced a dark pigment that was not observed in the wild type. Gene expression data showed that although AflR is expressed at normal levels, a number of aflatoxin biosynthesis genes are expressed at reduced levels in both nsd mutants. Expression of aflD, aflM, and aflP was greatly reduced in nsdC mutants, and neither aflatoxin nor the proteins for these genes could be detected. Our results support previous studies showing that there is a strong association between conidiophore and sclerotium development and aflatoxin production in A. flavus.
Collapse
|
15
|
Role of nitric oxide and flavohemoglobin homolog genes in Aspergillus nidulans sexual development and mycotoxin production. Appl Environ Microbiol 2011; 77:5524-8. [PMID: 21642398 DOI: 10.1128/aem.00638-11] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Flavohemoglobins are widely distributed in both prokaryotes and eukaryotes. These proteins are involved in reducing nitric oxide levels. Deletion of the Aspergillus nidulans flavohemoglobin gene fhbA induced sexual development and decreased sterigmatocystin production. Supplementation with a nitric oxide-releasing compound promoted cleistothecial formation and increased nsdD and steA expression, indicating that nitric oxide induces sexual development. This is the first study on the effect of nitric oxide on morphogenesis and secondary metabolism in fungi.
Collapse
|
16
|
Cary JW, Ehrlich KC, Beltz SB, Harris-Coward P, Klich MA. Characterization of the Aspergillus ochraceoroseus aflatoxin/sterigmatocystin biosynthetic gene cluster. Mycologia 2009; 101:352-62. [PMID: 19537208 DOI: 10.3852/08-173] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Production of carcinogenic aflatoxins has been reported from members of Aspergillus section Flavi, Aspergillus section Nidulantes and a newly proposed Aspergillus section Ochraceorosei that consists of Aspergillus ochraceoroseus and A. rambellii. Unlike members of section Flavi, A. ochraceoroseus and A. rambellii have been shown to accumulate both aflatoxin (AF) and the aflatoxin precursor sterigmatocystin (ST). Alhough morphologically distinct from A. nidulans, molecular characterization of A. ochraceoroseus AF/ST genes and physiological characteristics of AF/ST production indicated that A. ochraceoroseus is more closely related to A. nidulans than to A. flavus. Knowing that the A. nidulans ST gene cluster is organized differently from the A. flavus AF gene cluster, we determined the genetic organization of the AF/ST biosynthetic cluster in A. ochraceoroseus. Sequencing of overlapping lambda clones and genomic PCR fragments obtained by gene-walking techniques demonstrated that the A. ochraceoroseus AF/ST gene cluster is organized much like the A. nidulans ST gene cluster except that the region from aflN to aflW is located directly upstream of aflC and in reverse orientation such that aflW represents the distal end and aflY the proximal end of the cluster. The A. ochraceoroseus cluster genes demonstrated 62-76% nucleotide identity to their A. nidulans ST cluster gene homologs. Transformation of an A. nidulans aflR mutant with the A. ochraceoroseus aflR restored ST production in A. nidulans transformants. PCR amplification of A. rambellii genomic DNA demonstrated that the AF/ST gene cluster is organized in the same manner as that of A. ochraceoroseus.
Collapse
Affiliation(s)
- J W Cary
- USDA, ARS, Southern Regional Research Center, 1100 Robert E. Lee Boulevard, New Orleans, Louisiana 70124, USA.
| | | | | | | | | |
Collapse
|
17
|
Expression of a heterologous laccase by Aspergillus niger cultured by solid-state and submerged fermentations. Enzyme Microb Technol 2006. [DOI: 10.1016/j.enzmictec.2005.07.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
18
|
Abstract
The selection arena hypothesis states that overproduction of zygotes--a widespread phenomenon in animals and plants--can be explained as a mechanism of progeny choice. As a similar mechanism, the ascomycetous fungus Aspergillus nidulans may overproduce dikaryotic fruit initials, hereafter called dikaryons. Then, progeny choice might involve selection on which of these dikaryons will thrive to produce thousands of zygotes. These zygotes each produce eight sexual spores which together fill up one fruiting body. In this study, we test the selection arena hypothesis in this homothallic fungus that produces both sexual and asexual spores. We analyzed two mitochondrial and 15 auxotrophic mutations for consequences on sexual and asexual reproduction. We found that many of these mutations confer sexual self-sterility as a pleiotropic effect under conditions of normal asexual spore production. This confirms an important prediction of the selection arena, namely that dikaryons carrying a (slightly) deleterious mutation are not able to proliferate and produce sexual spores. The selection arena ensures that reproductive energy is invested mainly in dikaryons and thus sexual spores of good genetic quality.
Collapse
Affiliation(s)
- Judith Bruggeman
- Laboratory of Genetics, Department of Plant Sciences, Wageningen University, Arboretumlaan 4, 6703 BD Wageningen, The Netherlands
| | | | | |
Collapse
|
19
|
Swart K, van Heemst D, Slakhorst M, Debets F, Heyting C. Isolation and characterization of sexual sporulation mutants of Aspergillus nidulans. Fungal Genet Biol 2001; 33:25-35. [PMID: 11407883 DOI: 10.1006/fgbi.2001.1266] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
For the genetic dissection of sexual sporulation in Aspergillus nidulans, we started a collection of ascosporeless mutants. After mutagenization of conidiospores with high doses of UV, we isolated 20 mutants with defects in ascospore formation. We crossed these mutants in two successive rounds with the wild-type strain. Eighteen of the 20 isolated mutants produced progeny with the original mutant phenotype in these crosses, and these mutants were further analyzed. All 18 analyzed mutations were recessive to wild type. We assigned them to 15 complementation groups, based on crosses between mutants. The mutants could be classified as follows according to their cytological phenotype: (1) no croziers, (2) arrest at prekaryogamy, (3) arrest in early meiotic prophase, (4) arrest in late meiotic prophase, (5) arrest in meiotic metaphase I, (6) defective postmeiotic mitosis and/or deliniation of ascospores, and (7) slow progression through the postmeiotic stages of ascospore formation. A large proportion of the mutants, namely 11 of 18, arrested in meiotic prophase or metaphase I. We discuss a possible approach for isolating the wild-type alleles of the genes that carry the sexual sporulation mutations.
Collapse
Affiliation(s)
- K Swart
- Genetics and Molecular Genetics Groups, Wageningen University, Wageningen, 6703 HA, The Netherlands
| | | | | | | | | |
Collapse
|
20
|
Jeong HY, Han DM, Jahng KY, Chae KS. The rpl16a gene for ribosomal protein L16A identified from expressed sequence tags is differentially expressed during sexual development of Aspergillus nidulans. Fungal Genet Biol 2000; 31:69-78. [PMID: 11170736 DOI: 10.1006/fgbi.2000.1233] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We obtained 305 expressed sequence tags (ESTs), which are from the poly(A) site to the most proximal MboI site, from mycelia at the early sexual developmental (ESD) stage of Aspergillus nidulans. By comparison of these ESTs with those obtained previously from the vegetative stage and from the late sexual developmental stage followed by Northern blot analyses, genes of 17 ESTs were identified as being expressed more abundantly at the ESD stage than at the vegetative stage. Five of 17 genes were expressed more abundantly in the presence of the veA gene or the nsdD gene, suggesting that these 5 genes may be involved in sexual development. In a gene of one EST, appearing three times among 305 ESTs and identified by GenBank, polyadenylation seemed to occur at two sites. Nucleotide sequences of the gene having the EST and its cDNA revealed that the gene can code for a 202-amino-acid polypeptide with an estimated molecular mass of 23 kDa. The deduced amino acid showed 73% identity to Saccharomyces cerevisiae ribosomal protein L16A (RPL16A), and therefore the gene was named rpl16a. A. nidulans RPL16A had a putative leucine zipper motif and a basic leucine zipper motif like those of other organisms. The expression level of the rpl16a gene, present as a single copy in this organism, reached a maximum after 2 h, decreased thereafter, and increased again 30 to 50 h after the end of induction of sexual development. These results clearly indicated that the rpl16a gene is expressed differentially during sexual development.
Collapse
Affiliation(s)
- H Y Jeong
- Institute for Molecular Biology and Genetics, and Division of Biological Sciences, Chonbuk National University, Chonju, 561-756, Republic of Korea
| | | | | | | |
Collapse
|
21
|
Hoffmann B, Wanke C, Lapaglia SK, Braus GH. c-Jun and RACK1 homologues regulate a control point for sexual development in Aspergillus nidulans. Mol Microbiol 2000; 37:28-41. [PMID: 10931303 DOI: 10.1046/j.1365-2958.2000.01954.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Amino acid limitation results in impaired sexual fruit body formation in filamentous fungi such as Aspergillus nidulans. The starvation signal is perceived by the cross-pathway regulatory network controlling the biosynthesis of translational precursors and results in increased expression of a transcriptional activator encoded by a c-Jun homologue. In the presence of amino acids, the gene product of the mammalian RACK1 homologue cpcB is required to repress the network. Growth under amino acid starvation conditions permits the initiation of the sexual developmental programme of the fungus, but blocks fruit body formation before completion of meiosis. Accordingly, arrest at this defined control point results in microcleistothecia filled with hyphae. Addition of amino acids results in release of the block and completion of development to mature ascospores. The same developmental block is induced by either overexpression of c-Jun homologues or deletion of the RACK1 homologue cpcB of A. nidulans in the presence of amino acids. Therefore, the amino acid starvation signal regulates sexual development through the network that also controls the amino acid biosynthetic genes. Expression of the RACK1 gene suppresses the block in development caused by a deletion of cpcB. These data illuminate a connection between metabolism and sexual development in filamentous fungi.
Collapse
Affiliation(s)
- B Hoffmann
- Institute of Microbiology and Genetics, Georg-August-University, Grisebachstrasse 8, D-37077 Göttingen, Germany
| | | | | | | |
Collapse
|
22
|
Horng JS, Linz JE, Pestka JJ. Cloning and characterization of the trpC gene from an aflatoxigenic strain of Aspergillus parasiticus. Appl Environ Microbiol 1989; 55:2561-8. [PMID: 2690735 PMCID: PMC203122 DOI: 10.1128/aem.55.10.2561-2568.1989] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The trpC gene in the tryptophan biosynthetic pathway was isolated from an aflatoxigenic Aspergillus parasiticus by complementation of an Escherichia coli trpC mutant lacking phosphoribosylanthranilate isomerase (PRAI) activity. The cloned gene complemented an E. coli trpC mutant deficient in indoleglycerolphosphate synthase (IGPS) activity as well as an Aspergillus nidulans mutant strain that was defective in all three enzymatic activities of the trpC gene (glutamine amidotransferase, IGPS, and PRAI), thus indicating the presence of a complete and functional trpC gene. The location and organization of the A. parasiticus trpC gene on the cloned DNA fragment were determined by deletion mapping and by hybridization to heterologous DNA probes that were prepared from cloned trpC genes of A. nidulans and Aspergillus niger. These experiments suggested that the A. parasiticus trpC gene encoded a trifunctional polypeptide with a functional domain structure organized identically to those of analogous genes from other filamentous fungi. The A. parasiticus trpC gene was expressed constitutively regardless of the nutritional status of the culture medium. This gene should be useful as a selectable marker in developing a DNA-mediated transformation system to analyze the aflatoxin biosynthetic pathway of A. parasiticus.
Collapse
Affiliation(s)
- J S Horng
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing 48824
| | | | | |
Collapse
|
23
|
Abstract
We investigated the functional organization of the Aspergillus nidulans trpC promoter by the sequential removal of sequences upstream of the major trpC mRNA cap site (+1). DNA fragments containing promoter mutations were fused to the Escherichia coli lacZ gene, and a novel method was used to select for integration of the fusion gene at the Aspergillus argB locus. beta-Galactosidase assays and S1 nuclease protection experiments demonstrated that the promoter mutations affected gene expression in three ways: (i) 5' deletions up to -82 resulted in variable increases in beta-galactosidase activity, depending on the growth conditions; (ii) a deletion from -67 to -11 did not alter the level of beta-galactosidase activity, but did give rise to mRNAs with aberrant 5' ends; and (iii) a 5' deletion with an endpoint at -11 and an internal deletion from -142 to -11 abolished gene expression. These results indicate that sequences upstream of -82 reduce transcription of the trpC gene and that distinct DNA sequence elements are required for expression versus correct initiation of transcription of the trpC gene. The sequences essential for trpC expression do not include the common eucaryotic promoter elements CCAAT and TATAAA. To our knowledge, this is the first functional analysis of a promoter from a fungus other than Saccharomyces cerevisiae.
Collapse
|
24
|
Abstract
We investigated the functional organization of the Aspergillus nidulans trpC promoter by the sequential removal of sequences upstream of the major trpC mRNA cap site (+1). DNA fragments containing promoter mutations were fused to the Escherichia coli lacZ gene, and a novel method was used to select for integration of the fusion gene at the Aspergillus argB locus. beta-Galactosidase assays and S1 nuclease protection experiments demonstrated that the promoter mutations affected gene expression in three ways: (i) 5' deletions up to -82 resulted in variable increases in beta-galactosidase activity, depending on the growth conditions; (ii) a deletion from -67 to -11 did not alter the level of beta-galactosidase activity, but did give rise to mRNAs with aberrant 5' ends; and (iii) a 5' deletion with an endpoint at -11 and an internal deletion from -142 to -11 abolished gene expression. These results indicate that sequences upstream of -82 reduce transcription of the trpC gene and that distinct DNA sequence elements are required for expression versus correct initiation of transcription of the trpC gene. The sequences essential for trpC expression do not include the common eucaryotic promoter elements CCAAT and TATAAA. To our knowledge, this is the first functional analysis of a promoter from a fungus other than Saccharomyces cerevisiae.
Collapse
|
25
|
Sánchez F, Touriño A, Traseira S, Pérez-Aranda A, Rubio V, Peñalva MA. Molecular cloning and characterization of the trpC gene from Penicillium chrysogenum. MOLECULAR & GENERAL GENETICS : MGG 1986; 205:248-52. [PMID: 2433566 DOI: 10.1007/bf00430435] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We cloned the Penicillium chrysogenum trpC gene from a genomic library by complementation of an Escherichia coli trpC mutant lacking phosphoribosylanthranilate isomerase activity. The gene encodes a 2.7 kb poly(A)+ RNA. We localized the gene by sequence analysis in a 2.9 kb DNA insert found in the smallest plasmid selected from the library. Sequence data strongly suggest that the organization of the gene is similar to that described in other Ascomycetes. We found that a DNA fragment which codes only for the carboxy-terminal portion of the polypeptide is sufficient for complementation of the E. coli trpC9830 mutation.
Collapse
|
26
|
Muñoz-Rivas AM, Specht CA, Ullrich RC, Novotny CP. Isolation of the DNA sequence coding indole-3-glycerol phosphate synthetase and phosphoribosylanthranilate isomerase of Schizophyllum commune. Curr Genet 1986; 10:909-13. [PMID: 3447744 DOI: 10.1007/bf00398288] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A Schizophyllum gene library was made in plasmid pRK9. Plasmids from this library were tested for their ability to complement several auxotrophic mutations of Escherichia coli. The goal was to isolate a Schizophyllum auxotrophic gene that could be used to transform a corresponding Schizophyllum auxotrophic mutant to prototrophy. Complementation was observed only for E. coli trpC indole 3-glycerol phosphate synthetase (IGPS) and phosphoribosyl-anthranilate isomerase (PRAI) mutations. Plasmids with a Schizophyllum sequence coding for both IGPS and PRAI activities were recovered from E. coli transformants. Expression of the Schizophyllum gene (TRP1) in E. coli is probably dependent on the Serratia marcescens promoter of plasmid pRK9. The DNA sequence containing the Schizophyllum TRP1 gene was not obviously rearranged in cloning.
Collapse
Affiliation(s)
- A M Muñoz-Rivas
- Department of Botany, University of Vermont, Burlington 05405
| | | | | | | |
Collapse
|
27
|
Mullaney EJ, Hamer JE, Roberti KA, Yelton MM, Timberlake WE. Primary structure of the trpC gene from Aspergillus nidulans. MOLECULAR & GENERAL GENETICS : MGG 1985; 199:37-45. [PMID: 3158796 DOI: 10.1007/bf00327506] [Citation(s) in RCA: 161] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
We have determined the structure and complete nucleotide sequence of the trifunctional trpC gene from the Ascomycetous fungus Aspergillus nidulans. Results from RNA gel blot analyses showed that this gene encodes two size classes of polyribosomal, poly (A)+RNAs with approximate lengths of 2,400 and 2,600 nucleotides. S1 nuclease protection studies demonstrated that the distribution into the two size classes is due to selection of alternative sites for polyadenylation. The transcription units contain a single open translation reading frame of 2,304 nucleotides. The sequence of this reading frame is approximately 40% divergent from the sequence of the functionally analogous trp-1 gene from Neurospora crassa (Schechtman, M.G. and Yanofsky, C., J. Mol. Appl. Gen. 2:83-99). The predicted amino acid sequence of the A. nidulans trpC polypeptide is also 40% divergent from the predicted amino acid sequence of the N. crassa trp-1 polypeptide. The A. nidulans gene has considerably less bias in codon selection than observed for the N. crassa gene. Discrete regions of DNA homology were also found in similar positions in the 5' and 3' flanking sequences of the Aspergillus and Neurospora genes. Similar regions of homology were not observed in other Aspergillus or Neurospora genes that have been sequenced. Thus, if these evolutionarily conserved sequences act as signals for transcription initiation or polyadenylation, or are involved in gene regulation, their functions are restricted to a subset of protein coding genes in these two closely related fungi.
Collapse
|
28
|
Kos A, Kuijvenhoven J, Wernars K, Bos CJ, van den Broek HW, Pouwels PH, van den Hondel CA. Isolation and characterization of the Aspergillus niger trpC gene. Gene 1985; 39:231-8. [PMID: 2936650 DOI: 10.1016/0378-1119(85)90317-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The Aspergillus niger trpC gene was isolated by complementation experiments with an Escherichia coli trpC mutant. Plasmid DNA containing the A. niger trpC gene transforms an Aspergillus nidulans mutant strain, defective in all three enzymatic activities of the trpC gene, to Trp+, indicating the presence of a complete and functional trpC gene. Southern blot analysis of DNA from these Trp+ transformants showed that plasmid DNA was present but that this DNA was not integrated at the site of the chromosomal trpC locus. The A. niger trpC gene was localized on the cloned fragment by heterologous hybridization experiments and sequence analysis. These experiments suggest that the organization of the A. niger trpC gene is identical to that of the analogous A. nidulans trpC and the Neurospora crassa trp-1 genes.
Collapse
|
29
|
Yelton MM, Hamer JE, Timberlake WE. Transformation of Aspergillus nidulans by using a trpC plasmid. Proc Natl Acad Sci U S A 1984; 81:1470-4. [PMID: 6324193 PMCID: PMC344858 DOI: 10.1073/pnas.81.5.1470] [Citation(s) in RCA: 553] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We constructed a chimeric plasmid carrying a complete copy of the trifunctional trpC gene from the Ascomycete fungus Aspergillus nidulans. This plasmid, designated pHY201, replicates in Escherichia coli, where it confers resistance to ampicillin and chloramphenicol and complements trpC mutants lacking phosphoribosylanthranilate isomerase activity. We used pHY201 to transform an A. nidulans trpC- strain to trpC+ at frequencies of greater than 20 stable transformants per microgram of DNA. Southern blot analysis of DNA from transformants showed that pHY201 DNA had integrated into the A. nidulans chromosomes in a majority of cases. Most of the integration events appeared to occur at the site of the trpC- allele of the recipient strain. In several instances, we succeeded in recovering pHY201, or derivatives thereof, from A. nidulans transformants by restriction endonuclease digestion of chromosomal DNA, ligation, and transformation of E. coli.
Collapse
|
30
|
Yelton MM, Hamer JE, de Souza ER, Mullaney EJ, Timberlake WE. Developmental regulation of the Aspergillus nidulans trpC gene. Proc Natl Acad Sci U S A 1983; 80:7576-80. [PMID: 6324178 PMCID: PMC534383 DOI: 10.1073/pnas.80.24.7576] [Citation(s) in RCA: 65] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We have cloned the trifunctional trpC gene from Aspergillus nidulans by hybrid phage lambda complementation of an Escherichia coli trpC mutant lacking phosphoribosylanthranilate isomerase activity. Four different phages sharing a 4.3-kilobase region were obtained. Plasmid subclones containing this region also complemented the E. coli trpC mutant. We determined that a 1.8-kilobase DNA fragment was minimally required for complementation. The fragment hybridized with two poly(A)+ RNAs, 3.0 and 3.2 kilobases in length. We infer that these transcripts are Aspergillus trpC mRNAs and that the entire Aspergillus trpC gene is not required for complementation in E. coli. Levels of both trpC transcripts in poly(A)+ RNA are regulated by growth medium composition. They were highest when cells were grown in minimal medium containing nitrate as the nitrogen source and lowest when cells were grown in medium containing yeast extract. The concentrations of the transcripts are also regulated during conidiophore development. Conidiating cultures grown on medium containing yeast extract had significantly higher levels of both transcripts than did hyphae grown in minimal medium containing nitrate. Levels of the transcripts in mature spores were equivalent to those found in hyphae grown in minimal medium containing nitrate. Results from nutritional experiments with an A. nidulans trpC mutant suggest that developmental regulation of trpC mRNA levels may be related to a high requirement for tryptophan or a compound derived from tryptophan during conidiation.
Collapse
|