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Noar RD, Thomas E, Daub ME. Genetic Characteristics and Metabolic Interactions between Pseudocercospora fijiensis and Banana: Progress toward Controlling Black Sigatoka. PLANTS (BASEL, SWITZERLAND) 2022; 11:948. [PMID: 35406928 PMCID: PMC9002641 DOI: 10.3390/plants11070948] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 03/23/2022] [Accepted: 03/25/2022] [Indexed: 05/10/2023]
Abstract
The international importance of banana and severity of black Sigatoka disease have led to extensive investigations into the genetic characteristics and metabolic interactions between the Dothideomycete Pseudocercospora fijiensis and its banana host. P. fijiensis was shown to have a greatly expanded genome compared to other Dothideomycetes, due to the proliferation of retrotransposons. Genome analysis suggests the presence of dispensable chromosomes that may aid in fungal adaptation as well as pathogenicity. Genomic research has led to the characterization of genes and metabolic pathways involved in pathogenicity, including: secondary metabolism genes such as PKS10-2, genes for mitogen-activated protein kinases such as Fus3 and Slt2, and genes for cell wall proteins such as glucosyl phosphatidylinositol (GPI) and glycophospholipid surface (Gas) proteins. Studies conducted on resistance mechanisms in banana have documented the role of jasmonic acid and ethylene pathways. With the development of banana transformation protocols, strategies for engineering resistance include transgenes expressing antimicrobial peptides or hydrolytic enzymes as well as host-induced gene silencing (HIGS) targeting pathogenicity genes. Pseudocercospora fijiensis has been identified as having high evolutionary potential, given its large genome size, ability to reproduce both sexually and asexually, and long-distance spore dispersal. Thus, multiple control measures are needed for the sustainable control of black Sigatoka disease.
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Affiliation(s)
- Roslyn D. Noar
- NSF Center for Integrated Pest Management, North Carolina State University, Raleigh, NC 27606, USA
| | - Elizabeth Thomas
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA; (E.T.); (M.E.D.)
| | - Margaret E. Daub
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA; (E.T.); (M.E.D.)
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Witte TE, Villeneuve N, Boddy CN, Overy DP. Accessory Chromosome-Acquired Secondary Metabolism in Plant Pathogenic Fungi: The Evolution of Biotrophs Into Host-Specific Pathogens. Front Microbiol 2021; 12:664276. [PMID: 33968000 PMCID: PMC8102738 DOI: 10.3389/fmicb.2021.664276] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 03/09/2021] [Indexed: 11/25/2022] Open
Abstract
Accessory chromosomes are strain- or pathotype-specific chromosomes that exist in addition to the core chromosomes of a species and are generally not considered essential to the survival of the organism. Among pathogenic fungal species, accessory chromosomes harbor pathogenicity or virulence factor genes, several of which are known to encode for secondary metabolites that are involved in plant tissue invasion. Accessory chromosomes are of particular interest due to their capacity for horizontal transfer between strains and their dynamic "crosstalk" with core chromosomes. This review focuses exclusively on secondary metabolism (including mycotoxin biosynthesis) associated with accessory chromosomes in filamentous fungi and the role accessory chromosomes play in the evolution of secondary metabolite gene clusters. Untargeted metabolomics profiling in conjunction with genome sequencing provides an effective means of linking secondary metabolite products with their respective biosynthetic gene clusters that reside on accessory chromosomes. While the majority of literature describing accessory chromosome-associated toxin biosynthesis comes from studies of Alternaria pathotypes, the recent discovery of accessory chromosome-associated biosynthetic genes in Fusarium species offer fresh insights into the evolution of biosynthetic enzymes such as non-ribosomal peptide synthetases (NRPSs), polyketide synthases (PKSs) and regulatory mechanisms governing their expression.
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Affiliation(s)
- Thomas E. Witte
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre, Ottawa, ON, Canada
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, Canada
| | - Nicolas Villeneuve
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre, Ottawa, ON, Canada
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, Canada
| | - Christopher N. Boddy
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, Canada
| | - David P. Overy
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre, Ottawa, ON, Canada
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Lind AL, Wisecaver JH, Lameiras C, Wiemann P, Palmer JM, Keller NP, Rodrigues F, Goldman GH, Rokas A. Drivers of genetic diversity in secondary metabolic gene clusters within a fungal species. PLoS Biol 2017; 15:e2003583. [PMID: 29149178 PMCID: PMC5711037 DOI: 10.1371/journal.pbio.2003583] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 12/01/2017] [Accepted: 11/02/2017] [Indexed: 12/30/2022] Open
Abstract
Filamentous fungi produce a diverse array of secondary metabolites (SMs) critical for defense, virulence, and communication. The metabolic pathways that produce SMs are found in contiguous gene clusters in fungal genomes, an atypical arrangement for metabolic pathways in other eukaryotes. Comparative studies of filamentous fungal species have shown that SM gene clusters are often either highly divergent or uniquely present in one or a handful of species, hampering efforts to determine the genetic basis and evolutionary drivers of SM gene cluster divergence. Here, we examined SM variation in 66 cosmopolitan strains of a single species, the opportunistic human pathogen Aspergillus fumigatus. Investigation of genome-wide within-species variation revealed 5 general types of variation in SM gene clusters: nonfunctional gene polymorphisms; gene gain and loss polymorphisms; whole cluster gain and loss polymorphisms; allelic polymorphisms, in which different alleles corresponded to distinct, nonhomologous clusters; and location polymorphisms, in which a cluster was found to differ in its genomic location across strains. These polymorphisms affect the function of representative A. fumigatus SM gene clusters, such as those involved in the production of gliotoxin, fumigaclavine, and helvolic acid as well as the function of clusters with undefined products. In addition to enabling the identification of polymorphisms, the detection of which requires extensive genome-wide synteny conservation (e.g., mobile gene clusters and nonhomologous cluster alleles), our approach also implicated multiple underlying genetic drivers, including point mutations, recombination, and genomic deletion and insertion events as well as horizontal gene transfer from distant fungi. Finally, most of the variants that we uncover within A. fumigatus have been previously hypothesized to contribute to SM gene cluster diversity across entire fungal classes and phyla. We suggest that the drivers of genetic diversity operating within a fungal species shown here are sufficient to explain SM cluster macroevolutionary patterns. All organisms produce metabolites, which are small molecules important for growth, reproduction, and other essential functions. Some organisms, including fungi, plants, and bacteria, make specialized forms of metabolites known as “secondary” metabolites that are ecologically important and improve their producers’ chances of survival and reproduction. In fungi, the genes in pathways that synthesize secondary metabolites are typically located next to each other in the genome and organized in contiguous gene clusters. These gene clusters, along with the metabolites they produce, are highly distinct, even between otherwise similar fungi, and it is often difficult to reconstruct how these differences evolved. To understand how secondary metabolic pathways evolve in fungi, we compared secondary metabolic gene clusters in 66 strains of one species of filamentous fungus, the human pathogen Aspergillus fumigatus. We show that these gene clusters vary extensively within this species, and describe the genetic processes that cause these differences. We identify 5 types of variants: single nucleotide changes, gene and gene cluster gain and loss, different gene clusters at the same genomic position, and mobile gene clusters that “jump” around the genome. These results provide a road map to the types and frequencies of genomic changes underlying the extensive diversity of fungal secondary metabolites.
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Affiliation(s)
- Abigail L. Lind
- Department of Biomedical Informatics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Jennifer H. Wisecaver
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Catarina Lameiras
- Department of Microbiology, Portuguese Oncology Institute of Porto, Porto, Portugal
| | - Philipp Wiemann
- Department of Medical Microbiology & Immunology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Jonathan M. Palmer
- Center for Forest Mycology Research, Northern Research Station, US Forest Service, Madison, Wisconsin, United States of America
| | - Nancy P. Keller
- Department of Medical Microbiology & Immunology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Fernando Rodrigues
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal
- ICVS/3B′s - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Gustavo H. Goldman
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | - Antonis Rokas
- Department of Biomedical Informatics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
- * E-mail:
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Abstract
Metabolic gene clusters (MGCs) have provided some of the earliest glimpses at the biochemical machinery of yeast and filamentous fungi. MGCs encode diverse genetic mechanisms for nutrient acquisition and the synthesis/degradation of essential and adaptive metabolites. Beyond encoding the enzymes performing these discrete anabolic or catabolic processes, MGCs may encode a range of mechanisms that enable their persistence as genetic consortia; these include enzymatic mechanisms to protect their host fungi from their inherent toxicities, and integrated regulatory machinery. This modular, self-contained nature of MGCs contributes to the metabolic and ecological adaptability of fungi. The phylogenetic and ecological patterns of MGC distribution reflect the broad diversity of fungal life cycles and nutritional modes. While the origins of most gene clusters are enigmatic, MGCs are thought to be born into a genome through gene duplication, relocation, or horizontal transfer, and analyzing the death and decay of gene clusters provides clues about the mechanisms selecting for their assembly. Gene clustering may provide inherent fitness advantages through metabolic efficiency and specialization, but experimental evidence for this is currently limited. The identification and characterization of gene clusters will continue to be powerful tools for elucidating fungal metabolism as well as understanding the physiology and ecology of fungi.
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Affiliation(s)
- Jason C Slot
- The Ohio State University, Columbus, OH, United States.
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Abstract
The application of environmental DNA techniques and increased genome sequencing of microbial diversity, combined with detailed study of cellular characters, has consistently led to the reexamination of our understanding of the tree of life. This has challenged many of the definitions of taxonomic groups, especially higher taxonomic ranks such as eukaryotic kingdoms. The Fungi is an example of a kingdom which, together with the features that define it and the taxa that are grouped within it, has been in a continual state of flux. In this article we aim to summarize multiple lines of data pertinent to understanding the early evolution and definition of the Fungi. These include ongoing cellular and genomic comparisons that, we will argue, have generally undermined all attempts to identify a synapomorphic trait that defines the Fungi. This article will also summarize ongoing work focusing on taxon discovery, combined with phylogenomic analysis, which has identified novel groups that lie proximate/adjacent to the fungal clade-wherever the boundary that defines the Fungi may be. Our hope is that, by summarizing these data in the form of a discussion, we can illustrate the ongoing efforts to understand what drove the evolutionary diversification of fungi.
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Mehrabi R, Mirzadi Gohari A, Kema GHJ. Karyotype Variability in Plant-Pathogenic Fungi. ANNUAL REVIEW OF PHYTOPATHOLOGY 2017; 55:483-503. [PMID: 28777924 DOI: 10.1146/annurev-phyto-080615-095928] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Recent advances in genetic and molecular technologies gradually paved the way for the transition from traditional fungal karyotyping to more comprehensive chromosome biology studies. Extensive chromosomal polymorphisms largely resulting from chromosomal rearrangements (CRs) are widely documented in fungal genomes. These extraordinary CRs in fungi generate substantial genome plasticity compared to other eukaryotic organisms. Here, we review the most recent findings on fungal CRs and their underlying mechanisms and discuss the functional consequences of CRs for adaptation, fungal evolution, host range, and pathogenicity of fungal plant pathogens in the context of chromosome biology. In addition to a complement of permanent chromosomes called core chromosomes, the genomes of many fungal pathogens comprise distinct unstable chromosomes called dispensable chromosomes (DCs) that also contribute to chromosome polymorphisms. Compared to the core chromosomes, the structural features of DCs usually differ for gene density, GC content, housekeeping genes, and recombination frequency. Despite their dispensability for normal growth and development, DCs have important biological roles with respect to pathogenicity in some fungi but not in others. Therefore, their evolutionary origin is also reviewed in relation to overall fungal physiology and pathogenicity.
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Affiliation(s)
- Rahim Mehrabi
- Seed and Plant Improvement Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran
- Department of Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan, Iran
| | - Amir Mirzadi Gohari
- Department of Plant Pathology, Faculty of Agricultural Sciences and Engineering, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
- Wageningen Plant Research, Wageningen University and Research, 6700AA Wageningen, The Netherlands;
| | - Gert H J Kema
- Wageningen Plant Research, Wageningen University and Research, 6700AA Wageningen, The Netherlands;
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8
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Meiotic inheritance of a fungal supernumerary chromosome and its effect on sexual fertility in Nectria haematococca. Fungal Biol 2015; 119:929-939. [DOI: 10.1016/j.funbio.2015.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 06/25/2015] [Accepted: 07/14/2015] [Indexed: 11/20/2022]
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Kimura M, Tokai T, Takahashi-Ando N, Ohsato S, Fujimura M. Molecular and Genetic Studies ofFusariumTrichothecene Biosynthesis: Pathways, Genes, and Evolution. Biosci Biotechnol Biochem 2014; 71:2105-23. [PMID: 17827683 DOI: 10.1271/bbb.70183] [Citation(s) in RCA: 272] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Trichothecenes are a large family of sesquiterpenoid secondary metabolites of Fusarium species (e.g., F. graminearum) and other molds. They are major mycotoxins that can cause serious problems when consumed via contaminated cereal grains. In the past 20 years, an outline of the trichothecene biosynthetic pathway has been established based on the results of precursor feeding experiments and blocked mutant analyses. Following the isolation of the pathway gene Tri5 encoding the first committed enzyme trichodiene synthase, 10 biosynthesis genes (Tri genes; two regulatory genes, seven pathway genes, and one transporter gene) were functionally identified in the Tri5 gene cluster. At least three pathway genes, Tri101 (separated alone), and Tri1 and Tri16 (located in the Tri1-Tri16 two-gene cluster), were found outside of the Tri5 gene cluster. In this review, we summarize the current understanding of the pathways of biosynthesis, the functions of cloned Tri genes, and the evolution of Tri genes, focusing on Fusarium species.
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Affiliation(s)
- Makoto Kimura
- Plant & Microbial Metabolic Engineering Research Unit, Discovery Research Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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Wight WD, Labuda R, Walton JD. Conservation of the genes for HC-toxin biosynthesis in Alternaria jesenskae. BMC Microbiol 2013; 13:165. [PMID: 23865912 PMCID: PMC3729494 DOI: 10.1186/1471-2180-13-165] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 07/12/2013] [Indexed: 11/23/2022] Open
Abstract
Background HC-toxin, a cyclic tetrapeptide, is a virulence determinant for the plant pathogenic fungus Cochliobolus carbonum. It was recently discovered that another fungus, Alternaria jesenskae, also produces HC-toxin. Results The major genes (collectively known as AjTOX2) involved in the biosynthesis of HC-toxin were identified from A. jesenskae by genomic sequencing. The encoded orthologous proteins share 75-85% amino acid identity, and the genes for HC-toxin biosynthesis are duplicated in both fungi. The genomic organization of the genes in the two fungi show a similar but not identical partial clustering arrangement. A set of representative housekeeping proteins show a similar high level of amino acid identity between C. carbonum and A. jesenskae, which is consistent with the close relatedness of these two genera within the family Pleosporaceae (Dothideomycetes). Conclusions This is the first report that the plant virulence factor HC-toxin is made by an organism other than C. carbonum. The genes may have moved by horizontal transfer between the two species, but it cannot be excluded that they were present in a common ancestor and lost from other species of Alternaria and Cochliobolus.
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Affiliation(s)
- Wanessa D Wight
- Department of Energy Plant Research Laboratory, Michigan State University, 612 Wilson Road, Room 210, East Lansing, MI 48824, USA
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Condon BJ, Leng Y, Wu D, Bushley KE, Ohm RA, Otillar R, Martin J, Schackwitz W, Grimwood J, MohdZainudin N, Xue C, Wang R, Manning VA, Dhillon B, Tu ZJ, Steffenson BJ, Salamov A, Sun H, Lowry S, LaButti K, Han J, Copeland A, Lindquist E, Barry K, Schmutz J, Baker SE, Ciuffetti LM, Grigoriev IV, Zhong S, Turgeon BG. Comparative genome structure, secondary metabolite, and effector coding capacity across Cochliobolus pathogens. PLoS Genet 2013; 9:e1003233. [PMID: 23357949 PMCID: PMC3554632 DOI: 10.1371/journal.pgen.1003233] [Citation(s) in RCA: 148] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Accepted: 11/14/2012] [Indexed: 11/17/2022] Open
Abstract
The genomes of five Cochliobolus heterostrophus strains, two Cochliobolus sativus strains, three additional Cochliobolus species (Cochliobolus victoriae, Cochliobolus carbonum, Cochliobolus miyabeanus), and closely related Setosphaeria turcica were sequenced at the Joint Genome Institute (JGI). The datasets were used to identify SNPs between strains and species, unique genomic regions, core secondary metabolism genes, and small secreted protein (SSP) candidate effector encoding genes with a view towards pinpointing structural elements and gene content associated with specificity of these closely related fungi to different cereal hosts. Whole-genome alignment shows that three to five percent of each genome differs between strains of the same species, while a quarter of each genome differs between species. On average, SNP counts among field isolates of the same C. heterostrophus species are more than 25× higher than those between inbred lines and 50× lower than SNPs between Cochliobolus species. The suites of nonribosomal peptide synthetase (NRPS), polyketide synthase (PKS), and SSP-encoding genes are astoundingly diverse among species but remarkably conserved among isolates of the same species, whether inbred or field strains, except for defining examples that map to unique genomic regions. Functional analysis of several strain-unique PKSs and NRPSs reveal a strong correlation with a role in virulence.
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Affiliation(s)
- Bradford J. Condon
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
| | - Yueqiang Leng
- Department of Plant Pathology, North Dakota State University, Fargo, North Dakota, United States of America
| | - Dongliang Wu
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
| | - Kathryn E. Bushley
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, United States of America
| | - Robin A. Ohm
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Robert Otillar
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Joel Martin
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Wendy Schackwitz
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Jane Grimwood
- HudsonAlpha Institute for Biotechnology, Huntsville, Alabama, United States of America
| | - NurAinIzzati MohdZainudin
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
- Department of Biology, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
| | - Chunsheng Xue
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
- College of Plant Protection, Shenyang Agricultural University, Shenyang, China
| | - Rui Wang
- Department of Plant Pathology, North Dakota State University, Fargo, North Dakota, United States of America
| | - Viola A. Manning
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, United States of America
| | - Braham Dhillon
- Department of Forest Sciences, University of British Columbia, Vancouver, Canada
| | - Zheng Jin Tu
- Supercomputing Institute for Advanced Computational Research, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Brian J. Steffenson
- Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota, United States of America
| | - Asaf Salamov
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Hui Sun
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Steve Lowry
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Kurt LaButti
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - James Han
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Alex Copeland
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Erika Lindquist
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Kerrie Barry
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Jeremy Schmutz
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
- HudsonAlpha Institute for Biotechnology, Huntsville, Alabama, United States of America
| | - Scott E. Baker
- Pacific Northwest National Laboratory, Richland, Washington, United States of America
| | - Lynda M. Ciuffetti
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, United States of America
| | - Igor V. Grigoriev
- United States Department of Energy (DOE) Joint Genome Institute (JGI), Walnut Creek, California, United States of America
| | - Shaobin Zhong
- Department of Plant Pathology, North Dakota State University, Fargo, North Dakota, United States of America
| | - B. Gillian Turgeon
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
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Tsuge T, Harimoto Y, Akimitsu K, Ohtani K, Kodama M, Akagi Y, Egusa M, Yamamoto M, Otani H. Host-selective toxins produced by the plant pathogenic fungusAlternaria alternata. FEMS Microbiol Rev 2013; 37:44-66. [DOI: 10.1111/j.1574-6976.2012.00350.x] [Citation(s) in RCA: 247] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 06/14/2012] [Accepted: 07/19/2012] [Indexed: 12/19/2022] Open
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Horbach R, Navarro-Quesada AR, Knogge W, Deising HB. When and how to kill a plant cell: infection strategies of plant pathogenic fungi. JOURNAL OF PLANT PHYSIOLOGY 2011; 168:51-62. [PMID: 20674079 DOI: 10.1016/j.jplph.2010.06.014] [Citation(s) in RCA: 203] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Revised: 06/16/2010] [Accepted: 06/18/2010] [Indexed: 05/23/2023]
Abstract
Fungi cause severe diseases on a broad range of crop and ornamental plants, leading to significant economical losses. Plant pathogenic fungi exhibit a huge variability in their mode of infection, differentiation and function of infection structures and nutritional strategy. In this review, advances in understanding mechanisms of biotrophy, necrotrophy and hemibiotrophic lifestyles are described. Special emphasis is given to the biotrophy-necrotrophy switch of hemibiotrophic pathogens, and to biosynthesis, chemical diversity and mode of action of various fungal toxins produced during the infection process.
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Affiliation(s)
- Ralf Horbach
- Martin-Luther-University Halle-Wittenberg, Faculty of Natural Sciences III, Institute for Agricultural and Nutritional Sciences, Phytopathology and Plant Protection, Betty-Heimann-Strasse 3, Halle (Saale), Germany
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Seong KY, Pasquali M, Zhou X, Song J, Hilburn K, McCormick S, Dong Y, Xu JR, Kistler HC. Global gene regulation byFusariumtranscription factorsTri6andTri10reveals adaptations for toxin biosynthesis. Mol Microbiol 2009; 72:354-67. [DOI: 10.1111/j.1365-2958.2009.06649.x] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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15
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Andrie RM, Schoch CL, Hedges R, Spatafora JW, Ciuffetti LM. Homologs of ToxB, a host-selective toxin gene from Pyrenophora tritici-repentis, are present in the genome of sister-species Pyrenophora bromi and other members of the Ascomycota. Fungal Genet Biol 2007; 45:363-77. [PMID: 18226934 DOI: 10.1016/j.fgb.2007.10.014] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2007] [Revised: 10/20/2007] [Accepted: 10/23/2007] [Indexed: 11/29/2022]
Abstract
Pyrenophora tritici-repentis requires the production of host-selective toxins (HSTs) to cause the disease tan spot of wheat, including Ptr ToxA, Ptr ToxB, and Ptr ToxC. Pyrenophora bromi, the species most closely related to P. tritici-repentis, is the causal agent of brown leaf spot of bromegrass. Because of the relatedness of P. bromi and P. tritici-repentis, we investigated the possibility that P. bromi contains sequences homologous to ToxA and/or ToxB, the products of which may be involved in its interaction with bromegrass. Multiplex polymerase chain reaction (PCR) revealed the presence of ToxB-like sequences in P. bromi and high-fidelity PCR was used to clone several of these loci, which were subsequently confirmed to be homologous to ToxB. Additionally, Southern analysis revealed ToxB from P. bromi to have a multicopy nature similar to ToxB from P. tritici-repentis. A combination of phylogenetic and Southern analyses revealed that the distribution of ToxB extends further into the Pleosporaceae, and a search of available fungal genomes identified a distant putative homolog in Magnaporthe grisea, causal agent of rice blast. Thus, unlike most described HSTs, ToxB homologs are present across a broad range of plant pathogenic ascomycetes, suggesting that it may have arose in an early ancestor of the Ascomycota.
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Affiliation(s)
- Rachael M Andrie
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA
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van der Does HC, Rep M. Virulence genes and the evolution of host specificity in plant-pathogenic fungi. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2007; 20:1175-82. [PMID: 17918619 DOI: 10.1094/mpmi-20-10-1175] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In the fungal kingdom, the ability to cause disease in plants appears to have arisen multiple times during evolution. In many cases, the ability to infect particular plant species depends on specific genes that distinguish virulent fungi from their sometimes closely related nonvirulent relatives. These genes encode host-determining "virulence factors," including small, secreted proteins and enzymes involved in the synthesis of toxins. These virulence factors typically are involved in evolutionary arms races between plants and pathogens. We briefly summarize current knowledge of these virulence factors from several fungal species in terms of function, phylogenetic distribution, sequence variation, and genomic location. Second, we address some issues that are relevant to the evolution of virulence in fungi toward plants; in particular, horizontal gene transfer and the genomic organization of virulence genes.
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Affiliation(s)
- H Charlotte van der Does
- Swammerdam Institute for Life Sciences, University of Amsterdam, P.O. Box 94062, 1090 GB Amsterdam, The Netherlands
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Dekkers KL, You BJ, Gowda VS, Liao HL, Lee MH, Bau HJ, Ueng PP, Chung KR. The Cercospora nicotianae gene encoding dual O-methyltransferase and FAD-dependent monooxygenase domains mediates cercosporin toxin biosynthesis. Fungal Genet Biol 2007; 44:444-54. [PMID: 17074519 DOI: 10.1016/j.fgb.2006.08.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 08/28/2006] [Accepted: 08/30/2006] [Indexed: 11/27/2022]
Abstract
Cercosporin, a photo-activated, non-host-selective phytotoxin produced by many species of the plant pathogenic fungus Cercospora, causes peroxidation of plant cell membranes by generating reactive oxygen species and is an important virulence determinant. Here we report a new gene, CTB3 that is involved in cercosporin biosynthesis in Cercospora nicotianae. CTB3 is adjacent to a previously identified CTB1 encoding a polyketide synthase which is also required for cercosporin production. CTB3 contains a putative O-methyltransferase domain in the N-terminus and a putative flavin adenine dinucleotide (FAD)-dependent monooxygenase domain in the C-terminus. The N-terminal amino acid sequence also is similar to that of the transcription enhancer AFLS (formerly AFLJ) involved in aflatoxin biosynthesis. Expression of CTB3 was differentially regulated by light, medium, nitrogen and carbon sources and pH. Disruption of the N- or C-terminus of CTB3 yielded mutants that failed to accumulate the CTB3 transcript and cercosporin. The Deltactb3 disruptants produced a yellow pigment that is not toxic to tobacco suspension cells. Production of cercosporin in a Deltactb3 null mutant was fully restored when transformed with a functional CTB3 clone or when paired with a Deltactb1-null mutant (defective in polyketide synthase) by cross feeding of the biosynthetic intermediates. Pathogenicity assays using detached tobacco leaves revealed that the Deltactb3 disruptants drastically reduced lesion formation.
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Affiliation(s)
- Katherine L Dekkers
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Rd., Lake Alfred, FL 33850, USA
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18
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Luo CX, Yin LF, Ohtaka K, Kusaba M. The 1.6Mb chromosome carrying the avirulence gene AvrPik in Magnaporthe oryzae isolate 84R-62B is a chimera containing chromosome 1 sequences. ACTA ACUST UNITED AC 2006; 111:232-9. [PMID: 17188484 DOI: 10.1016/j.mycres.2006.10.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Revised: 10/14/2006] [Accepted: 10/25/2006] [Indexed: 10/23/2022]
Abstract
A genetic map was constructed previously from a cross between Magnaporthe oryzae isolates 84R-62B and Y93-245c-2, and genetic markers closely linked to the cultivar-specific avirulence (Avr) gene, AvrPik, were assigned to a 1.6Mb small chromosome of 84R-62B that is absent from Y93-245c-2. In the present study, the 1.6Mb chromosome was characterized by using contour-clamped homogeneous electric fields (CHEF) electrophoresis and hybridization analysis. CHEF electrophoresis analysis showed that the 1.6Mb chromosome was inherited in Mendelian fashion, and co-segregated with AvrPik. Southern hybridization analysis revealed that the 1.6Mb chromosome carried sequences only distributed to the supernumerary chromosome in M. oryzae isolates, as well as sequences corresponding to those in the supercontig 17 of chromosome 1 in the M. grisea database. Thus, we conclude that the Mendelian 1.6Mb chromosome is a chimera containing sequences from chromosome 1 and from supernumerary chromosomes in M. oryzae.
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Affiliation(s)
- Chao-Xi Luo
- Faculty of Agriculture, Saga University, Saga, Japan
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19
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Zhong S, Steffenson BJ. Molecular karyotyping and chromosome length polymorphism in Cochliobolus sativus. ACTA ACUST UNITED AC 2006; 111:78-86. [PMID: 17161941 DOI: 10.1016/j.mycres.2006.09.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Revised: 08/28/2006] [Accepted: 09/01/2006] [Indexed: 11/24/2022]
Abstract
Fungi are known to have variable genomes that can generate new virulence types capable of attacking important crop plants. To assess chromosome length polymorphisms in the barley spot blotch pathogen (Cochliobolus sativus), we analyzed the karyotypes of 16 isolates using contour-clamped homogeneous electric field (CHEF) electrophoresis. The collection of isolates studied were from diverse regions of the world (USA, Canada, Japan, Brazil, Uruguay, and Poland) and included representatives comprising the three known C. sativus pathotypes of 0, 1, and 2. Under two different running conditions, the number of CHEF bands observed ranged from 8 to 13 with a size range of 0.85 to 3.80 mega-bases (Mb). Each of the 16 isolates showed a unique banding pattern, except for two North Dakota isolates ND90Pr and ND91-Bowman, which were very similar. Single-copy DNA probes, previously assigned to each of the 15 chromosomes identified in reference isolate ND93-1, were hybridized to Southern blots of CHEF-separated chromosomes and revealed highly polymorphic chromosomes among isolates. Chromosomal rearrangements (translocations, deletions, duplications) were found in several isolates. DNA markers previously found linked to VHv1, a gene in pathotype 2 isolates conferring virulence on barley cultivar Bowman, also were used as probes in hybridizations with the CHEF blots. The results showed that the chromosome carrying the virulence gene in pathotype 2 isolates is larger than its counterpart without the gene in other isolates. This suggests that the genomic region carrying the virulence locus VHv1 is unique to pathotype 2 isolates. This study provides useful information on genome structure and divergence, which is essential for advancing our understanding of the genetics and biology of C. sativus.
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Affiliation(s)
- Shaobin Zhong
- Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108, USA.
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20
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Bok JW, Chung D, Balajee SA, Marr KA, Andes D, Nielsen KF, Frisvad JC, Kirby KA, Keller NP. GliZ, a transcriptional regulator of gliotoxin biosynthesis, contributes to Aspergillus fumigatus virulence. Infect Immun 2006; 74:6761-8. [PMID: 17030582 PMCID: PMC1698057 DOI: 10.1128/iai.00780-06] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gliotoxin is a nonribosomal peptide produced by Aspergillus fumigatus. This compound has been proposed as an A. fumigatus virulence factor due to its cytotoxic, genotoxic, and apoptotic properties. Recent identification of the gliotoxin gene cluster identified several genes (gli genes) likely involved in gliotoxin production, including gliZ, encoding a putative Zn(2)Cys(6) binuclear transcription factor. Replacement of gliZ with a marker gene (DeltagliZ) resulted in no detectable gliotoxin production and loss of gene expression of other gli cluster genes. Placement of multiple copies of gliZ in the genome increased gliotoxin production. Using endpoint survival data, the DeltagliZ and a multiple-copy gliZ strain were not statistically different from the wild type in a murine pulmonary model; however, both the wild-type and the multiple-copy gliZ strain were more virulent than DeltalaeA (a mutant reduced in production of gliotoxin and other toxins). A flow-cytometric analysis of polymorphonuclear leukocytes (PMNs) exposed to supernatants from wild-type, DeltagliZ, complemented DeltagliZ, and DeltalaeA strains supported a role for gliotoxin in apoptotic but not necrotic PMN cell death. This may indicate that several secondary metabolites are involved in A. fumigatus virulence.
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Affiliation(s)
- Jin Woo Bok
- Department of Plant Pathology, University of Wisconsin-Madison, 882 Russell Labs, 1630 Linden Drive, Madison, WI 53706, USA
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Katoh H, Isshiki A, Masunaka A, Yamamoto H, Akimitsu K. A Virulence-Reducing Mutation in the Postharvest Citrus Pathogen Alternaria citri. PHYTOPATHOLOGY 2006; 96:934-940. [PMID: 18944048 DOI: 10.1094/phyto-96-0934] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT Alternaria citri causes Alternaria black rot, a postharvest fruit disease, on a broad range of citrus cultivars. We previously described that an endopolygalacturonase minus mutant of A. citri caused significantly less black rot in citrus fruit. To search for other essential factors causing symptoms in addition to endopolygalacturonase, a random mutation analysis of pathogenicity was performed using restriction enzyme-mediated integration. Three isolates among 1,694 transformants of A. citri had a loss in pathogenicity in a citrus peel assay, and one of these three mutants was a histidine auxotroph. Gene AcIGPD that encodes imidazole glycerol phosphate dehydratase, the sixth enzyme in the histidine biosynthetic pathway, was cloned, and the mutant containing the disrupted target gene, AcIGPD, caused less black rot.
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22
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Abstract
HC-toxin is a cyclic tetrapeptide of structure cyclo(D-Pro-L-Ala-D-Ala-L-Aeo), where Aeo stands for 2-amino-9,10-epoxi-8-oxodecanoic acid. It is a determinant of specificity and virulence in the interaction between the producing fungus, Cochliobolus carbonum, and its host, maize. HC-toxin qualifies as one of the few microbial secondary metabolites whose ecological function in nature is understood. Reaction to C. carbonum and to HC-toxin is controlled in maize by the Hm1 and Hm2 loci. These loci encode HC-toxin reductase, which detoxifies HC-toxin by reducing the 8-carbonyl group of Aeo. HC-toxin is an inhibitor of histone deacetylases (HDACs) in many organisms, including plants, insects, and mammals, but why inhibition of HDACs during infection by C. carbonum leads to disease is not understood. The genes for HC-toxin biosynthesis (collectively known as the TOX2 locus) are loosely clustered over >500 kb in C. carbonum. All of the known TOX2 genes are present in multiple, functional copies and are absent from natural toxin non-producing isolates. The central enzyme in HC-toxin biosynthesis is a 570-kDa non-ribosomal synthetase encoded by a 15.7-kb open reading frame. Other genes known to be required for HC-toxin encode alpha and beta subunits of fatty acid synthase, which are presumed to contribute to the synthesis of Aeo; a pathway-specific transcription factor; an efflux carrier; a predicted branched-chain amino acid aminotransferase; and an alanine racemase.
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Affiliation(s)
- Jonathan D Walton
- Department of Energy Plant Research Laboratory, Michigan State University, E. Lansing, MI 48824, USA.
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Doddapaneni H, Chakraborty R, Yadav JS. Genome-wide structural and evolutionary analysis of the P450 monooxygenase genes (P450ome) in the white rot fungus Phanerochaete chrysosporium: evidence for gene duplications and extensive gene clustering. BMC Genomics 2005; 6:92. [PMID: 15955240 PMCID: PMC1184071 DOI: 10.1186/1471-2164-6-92] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2004] [Accepted: 06/14/2005] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Phanerochaete chrysosporium, the model white rot basidiomycetous fungus, has the extraordinary ability to mineralize (to CO2) lignin and detoxify a variety of chemical pollutants. Its cytochrome P450 monooxygenases have recently been implied in several of these biotransformations. Our initial P450 cloning efforts in P. chrysosporium and its subsequent whole genome sequencing have revealed an extraordinary P450 repertoire ("P450ome") containing at least 150 P450 genes with yet unknown function. In order to understand the functional diversity and the evolutionary mechanisms and significance of these hemeproteins, here we report a genome-wide structural and evolutionary analysis of the P450ome of this fungus. RESULTS Our analysis showed that P. chrysosporium P450ome could be classified into 12 families and 23 sub-families and is characterized by the presence of multigene families. A genome-level structural analysis revealed 16 organizationally homogeneous and heterogeneous clusters of tandem P450 genes. Analysis of our cloned cDNAs revealed structurally conserved characteristics (intron numbers and locations, and functional domains) among members of the two representative multigene P450 families CYP63 and CYP505 (P450foxy). Considering the unusually complex structural features of the P450 genes in this genome, including microexons (2-10 aa) and frequent small introns (45-55 bp), alternative splicing, as experimentally observed for CYP63, may be a more widespread event in the P450ome of this fungus. Clan-level phylogenetic comparison revealed that P. chrysosporium P450 families fall under 11 fungal clans and the majority of these multigene families appear to have evolved locally in this genome from their respective progenitor genes, as a result of extensive gene duplications and rearrangements. CONCLUSION P. chrysosporium P450ome, the largest known to date among fungi, is characterized by tandem gene clusters and multigene families. This enormous P450 gene diversity has evolved by extensive gene duplications and intragenomic recombinations of the progenitor genes presumably to meet the exceptionally high metabolic demand of this biodegradative group of basidiomycetous fungi in ecological niches. In this context, alternative splicing appears to further contribute to the evolution of functional diversity of the P450ome in this fungus. The evolved P450 diversity is consistent with the known vast biotransformation potential of P. chrysosporium. The presented analysis will help design future P450 functional studies to understand the underlying mechanisms of secondary metabolism and oxidative biotransformation pathways in this model white rot fungus.
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Affiliation(s)
- Harshavardhan Doddapaneni
- Environmental Genetics and Molecular Toxicology Division, Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0056, USA
| | - Ranajit Chakraborty
- The Center for Genome Information, Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0056, USA
| | - Jagjit S Yadav
- Environmental Genetics and Molecular Toxicology Division, Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0056, USA
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Schweizer E, Hofmann J. Microbial type I fatty acid synthases (FAS): major players in a network of cellular FAS systems. Microbiol Mol Biol Rev 2004; 68:501-17, table of contents. [PMID: 15353567 PMCID: PMC515254 DOI: 10.1128/mmbr.68.3.501-517.2004] [Citation(s) in RCA: 246] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The present review focuses on microbial type I fatty acid synthases (FASs), demonstrating their structural and functional diversity. Depending on their origin and biochemical function, multifunctional type I FAS proteins form dimers or hexamers with characteristic organization of their catalytic domains. A single polypeptide may contain one or more sets of the eight FAS component functions. Alternatively, these functions may split up into two different and mutually complementing subunits. Targeted inactivation of the individual yeast FAS acylation sites allowed us to define their roles during the overall catalytic process. In particular, their pronounced negative cooperativity is presumed to coordinate the FAS initiation and chain elongation reactions. Expression of the unlinked genes, FAS1 and FAS2, is in part constitutive and in part subject to repression by the phospholipid precursors inositol and choline. The interplay of the involved regulatory proteins, Rap1, Reb1, Abf1, Ino2/Ino4, Opi1, Sin3 and TFIIB, has been elucidated in considerable detail. Balanced levels of subunits alpha and beta are ensured by an autoregulatory effect of FAS1 on FAS2 expression and by posttranslational degradation of excess FAS subunits. The functional specificity of type I FAS multienzymes usually requires the presence of multiple FAS systems within the same cell. De novo synthesis of long-chain fatty acids, mitochondrial fatty acid synthesis, acylation of certain secondary metabolites and coenzymes, fatty acid elongation, and the vast diversity of mycobacterial lipids each result from specific FAS activities. The microcompartmentalization of FAS activities in type I multienzymes may thus allow for both the controlled and concerted action of multiple FAS systems within the same cell.
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Affiliation(s)
- Eckhart Schweizer
- Lehrstuhl für Biochemie der Universität Erlangen-Nürnberg, Staudtstrasse 5, Erlangen 91058, Germany
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25
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Lichter A, Gaventa JM, Ciuffetti LM. Chromosome-based molecular characterization of pathogenic and non-pathogenic wheat isolates of Pyrenophora tritici-repentis. Fungal Genet Biol 2002; 37:180-9. [PMID: 12409102 DOI: 10.1016/s1087-1845(02)00500-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The ToxA gene of Pyrenophora tritici-repentis encodes a host-selective toxin (Ptr ToxA) that has been shown to confer pathogenicity when used to transform a non-pathogenic wheat isolate. Major karyotype polymorphisms between pathogenic and non-pathogenic strains, and to a lesser extent among pathogenic strains, and among non-pathogenic strains were identified. ToxA was localized to a 3.0 Mb chromosome. PCR-based subtraction was carried out with the ToxA chromosome as tester DNA and genomic DNA from a non-pathogenic isolate as driver DNA. Seven of 8 single-copy probes that originated from the 3.0 Mb chromosome could be assigned to a 2.75 Mb chromosome of a non-pathogenic isolate. Nine different repetitive DNA probes originated from the 3.0 Mb chromosome, including sequences that correspond to known fungal transposable elements. Two additional single-copy probes that originated from a 3.4 Mb chromosome were unique to the pathogens and they correspond to a peptide synthetase gene. Our findings suggest substantial differences between pathogenic and non-pathogenic isolates of P. tritici-repentis.
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Affiliation(s)
- Amnon Lichter
- Department of Botany and Plant Pathology, Oregon State University, 2082 Cordley Hall, Corvallis, OR 97331-2902, USA
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27
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Baidyaroy D, Brosch G, Graessle S, Trojer P, Walton JD. Characterization of inhibitor-resistant histone deacetylase activity in plant-pathogenic fungi. EUKARYOTIC CELL 2002; 1:538-47. [PMID: 12456002 PMCID: PMC118000 DOI: 10.1128/ec.1.4.538-547.2002] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
HC-toxin, a cyclic peptide made by the filamentous fungus Cochliobolus carbonum, is an inhibitor of histone deacetylase (HDAC) from many organisms. It was shown earlier that the HDAC activity in crude extracts of C. carbonum is relatively insensitive to HC-toxin as well as to the chemically unrelated HDAC inhibitors trichostatin and D85, whereas the HDAC activity of Aspergillus nidulans is sensitive (G. Brosch et al., Biochemistry 40:12855-12863, 2001). Here we report that HC-toxin-resistant HDAC activity was present in other, but not all, plant-pathogenic Cochliobolus species but not in any of the saprophytic species tested. The HDAC activities of the fungi Alternaria brassicicola and Diheterospora chlamydosporia, which also make HDAC inhibitors, were resistant. The HDAC activities of all C. carbonum isolates tested, except one non-toxin-producing isolate, were resistant. In a cross between a sensitive isolate and a resistant isolate, resistance genetically cosegregated with HC-toxin production. When fractionated by anion-exchange chromatography, extracts of resistant and sensitive isolates and species had two peaks of HDAC activity, one that was fully HC-toxin resistant and a second that was larger and sensitive. The first peak was consistently smaller in extracts of sensitive fungi than in resistant fungi, but the difference appeared to be insufficiently large to explain the differential sensitivities of the crude extracts. Differences in mRNA expression levels of the four known HDAC genes of C. carbonum did not account for the observed differences in HDAC activity profiles. When mixed together, resistant extracts protected extracts of sensitive C. carbonum but did not protect other sensitive Cochlibolus species or Neurospora crassa. Production of this extrinsic protection factor was dependent on TOXE, the transcription factor that regulates the HC-toxin biosynthetic genes. The results suggest that C. carbonum has multiple mechanisms of self-protection against HC-toxin.
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Affiliation(s)
- Dipnath Baidyaroy
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
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Zhong S, Steffenson BJ, Martinez JP, Ciuffetti LM. A molecular genetic map and electrophoretic karyotype of the plant pathogenic fungus Cochliobolus sativus. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2002; 15:481-492. [PMID: 12036279 DOI: 10.1094/mpmi.2002.15.5.481] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A molecular genetic map was constructed and an electrophoretic karyotype was resolved for Cochliobolus sativus, the causal agent of spot blotch of barley and wheat. The genetic map consists of 27 linkage groups with 97 amplified fragment length polymorphism (AFLP) markers, 31 restriction fragment length polymorphism (RFLP) markers, two polymerase chain reaction amplified markers, the mating type locus (CsMAT), and a gene (VHv1) conditioning high virulence on barley cv. Bowman. These linkage groups covered a map distance of 849 cM. The virulence gene VHv1 cosegregated with six AFLP markers and was mapped on one of the major linkage groups. Fifteen chromosome-sized DNAs were resolved in C. sativus isolates ND93-1 and ND9OPr with contour-clamped homogeneous electric field (CHEF) electrophoresis combined with telomere probe analysis of comigrating chromosome-sized DNAs. The chromosome sizes ranged from 1.25 to 3.80 Mbp, and the genome size of the fungus was estimated to be approximately 33 Mbp. By hybridizing genetically mapped RFLP and AFLP markers to CHEF blots, 25 of the 27 linkage groups were assigned to specific chromosomes. The barley-specific virulence locus VHv1 was localized on a chromosome of 2.80 Mbp from isolate ND9OPr in the CHEF gel. The total map length of the fungus was estimated to be at least 1,329 cM based on the map distance covered by the linked markers and the estimated gaps. Therefore, the physical to genetic distance ratio is approximately 25 kb/cM. Construction of a high-resolution map around target loci will facilitate the cloning of the genes conferring virulence and other characters in C. sativus by a map-based cloning strategy.
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Affiliation(s)
- Shaobin Zhong
- Department of Plant Pathology, North Dakota State University, Fargo 58105, USA
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Ahn JH, Cheng YQ, Walton JD. An extended physical map of the TOX2 locus of Cochliobolus carbonum required for biosynthesis of HC-toxin. Fungal Genet Biol 2002; 35:31-8. [PMID: 11860263 DOI: 10.1006/fgbi.2001.1305] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In genetic crosses, HC-toxin production in the filamentous fungus Cochliobolus carbonum appears to be controlled by a single locus, TOX2. At the molecular level, TOX2 is composed of at least seven duplicated and coregulated genes involved in HC-toxin biosynthesis, export, and regulation. All copies of four of the TOX2 genes were previously mapped within a 540-kb stretch of DNA in strain SB111. Subsequently, an additional three TOX2 genes, TOXE, TOXF, and TOXG, have been discovered. In this paper we have mapped all copies of the new genes, a total of seven, and show that except for one of the two copies of TOXE, which was previously shown to be on a chromosome of 0.7 Mb in strain SB111, they are all linked to the previously known TOX2 genes within approximately 600 kb of each other on a chromosome of 3.5 Mb. We show here that this chromosome also contains at least one non-TOX2 gene, EXG2, which encodes an exo-beta1,3-glucanase. EXG2 is still present in strains that have undergone spontaneous deletion of up to approximately 1.4 Mb of the 3.5-Mb chromosome. The results contribute to our understanding of the complex organization of the genes involved in HC-toxin biosynthesis and are consistent with the hypothesis that a reciprocal chromosomal translocation accounts for the pattern of distribution of the TOX2 genes in different C. carbonum isolates.
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Affiliation(s)
- Joong-Hoon Ahn
- Department of Forest Resources, Konkuk University, Seoul, 143-701, Korea
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Wolpert TJ, Dunkle LD, Ciuffetti LM. Host-selective toxins and avirulence determinants: what's in a name? ANNUAL REVIEW OF PHYTOPATHOLOGY 2002; 40:251-85. [PMID: 12147761 DOI: 10.1146/annurev.phyto.40.011402.114210] [Citation(s) in RCA: 214] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Host-selective toxins, a group of structurally complex and chemically diverse metabolites produced by plant pathogenic strains of certain fungal species, function as essential determinants of pathogenicity or virulence. Investigations into the molecular and biochemical responses to these disease determinants reveal responses typically associated with host defense and incompatibility induced by avirulence determinants. The characteristic responses that unify these disparate disease phenotypes are numerous, yet the evidence implicating a causal relationship of these responses, whether induced by host-selective toxins or avirulence factors, in determining the consequences of the host-pathogen interaction is equivocal. This review summarizes some examples of the action of host-selective toxins to illustrate the similarity in responses with those to avirulence determinants.
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Affiliation(s)
- Thomas J Wolpert
- Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331, USA.
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31
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Affiliation(s)
- A E Osbourn
- Sainsbury Laboratory, John Innes Centre, Norwich NR4 7UH, United Kingdom.
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32
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Kim H, Ahn JH, Görlach JM, Caprari C, Scott-Craig JS, Walton JD. Mutational analysis of beta-glucanase genes from the plant-pathogenic fungus Cochliobolus carbonum. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2001; 14:1436-1443. [PMID: 11768539 DOI: 10.1094/mpmi.2001.14.12.1436] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Two new beta-glucanase-encoding genes, EXG2 and MLG2, were isolated from the plant-pathogenic fungus Cochliobolus carbonum using polymerase chain reaction based on amino acid sequences from the purified proteins. EXG2 encodes a 46.6-kDa exo-beta1,3-glucanase and is located on the same 3.5-Mb chromosome that contains the genes of HC-toxin biosynthesis. MLG2 encodes a 26.8-kDa mixed-linked (beta1,3-beta1,4) glucanase with low activity against beta1,4-glucan and no activity against beta1,3-glucan. Specific mutants of EXG2 and MLG2 were constructed by targeted gene replacement. Strains with multiple mutations (genotypes exg1/mlg1, exg2/mlg1, mlg1/mlg2, and exg1/exg2/mlg1/mlg2) were also constructed by sequential disruption and by crossing. Total mixed-linked glucanase activity in culture filtrates of mlg1/mlg2 and exg1/exg2/mlg1/mlg2 mutants was reduced by approximately 73%. Total beta1,3-glucanase activity was reduced by 10, 54, and 96% in exg2, mlg1, and exg1/exg2/mlg1/mlg2 mutants, respectively. The quadruple mutant showed only a modest decrease in growth on beta1,3-glucan or mixed-linked glucan. None of the mutants showed any decrease in virulence.
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Affiliation(s)
- H Kim
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing 48824, USA
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Churchill AC, Dunkle LD, Silbert W, Kennedy KJ, Macko V. Differential synthesis of peritoxins and precursors by pathogenic strains of the fungus Periconia circinata. Appl Environ Microbiol 2001; 67:5721-8. [PMID: 11722928 PMCID: PMC93365 DOI: 10.1128/aem.67.12.5721-5728.2001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Pathogenic strains of the soilborne fungus Periconia circinata produce peritoxins with host-selective toxicity against susceptible genotypes of sorghum. The peritoxins are low-molecular-weight, hybrid molecules consisting of a peptide and a chlorinated polyketide. Culture fluids from pathogenic, toxin-producing (Tox(+)) and nonpathogenic, non-toxin-producing (Tox(-)) strains were analyzed directly by gradient high-performance liquid chromatography (HPLC) with photodiode array detection and HPLC-mass spectrometry to detect intermediates and final products of the biosynthetic pathway. This approach allowed us to compare the metabolite profiles of Tox(+) and Tox(-) strains. Peritoxins A and B and the biologically inactive intermediates, N-3-(E-pentenyl)-glutaroyl-aspartate, circinatin, and 7-chlorocircinatin, were detected only in culture fluids of the Tox(+) strains. The latter two compounds were produced consistently by Tox(+) strains regardless of the amount of peritoxins produced under various culture conditions. In summary, none of the known peritoxin-related metabolites were detected in Tox(-) strains, which suggests that these strains may lack one or more functional genes required for peritoxin biosynthesis.
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Affiliation(s)
- A C Churchill
- Boyce Thompson Institute, Cornell University, Ithaca, New York 14853-1801, USA.
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Pedley KF, Walton JD. Regulation of cyclic peptide biosynthesis in a plant pathogenic fungus by a novel transcription factor. Proc Natl Acad Sci U S A 2001; 98:14174-9. [PMID: 11698648 PMCID: PMC61187 DOI: 10.1073/pnas.231491298] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Strains of the filamentous fungus Cochliobolus carbonum that produce the host-selective compound HC-toxin, a cyclic tetrapeptide, are highly virulent on certain genotypes of maize (Zea mays L.). Production of HC-toxin is under the control of a complex locus, TOX2, which is composed of at least seven linked and duplicated genes that are present only in toxin-producing strains of C. carbonum. One of these genes, TOXE, was earlier shown to be required for the expression of the other TOX2 genes. TOXE has four ankyrin repeats and a basic region similar to those found in basic leucine zipper (bZIP) proteins, but lacks any apparent leucine zipper. Here we show that TOXE is a DNA-binding protein that recognizes a ten-base motif (the "tox-box") without dyad symmetry that is present in the promoters of all of the known TOX2 genes. Both the basic region and the ankyrin repeats are involved in DNA binding. A region of TOXE that includes the first ankyrin repeat is necessary and sufficient for transcriptional activation in yeast. The data indicate that TOXE is the prototype of a new family of transcription factor, so far found only in plant-pathogenic fungi. TOXE plays a specific regulatory role in HC-toxin production and, therefore, pathogenicity by C. carbonum.
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Affiliation(s)
- K F Pedley
- Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
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Ahn JH, Sposato P, Kim SI, Walton JD. Molecular cloning and characterization of cel2 from the fungus Cochlibolus carbonum. Biosci Biotechnol Biochem 2001; 65:1406-11. [PMID: 11471744 DOI: 10.1271/bbb.65.1406] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A new cellulase gene, cel2, from the filamentous fungus Cochliobolus carbonum was cloned by using egl-1 of Trichoderma reesei as a heterologous probe. DNA blot analysis of cel2 showed that this gene is present as a single copy. The gene contains one 49-bp- intron. cel2 encodes a predicted protein (Cel2p) of 423 amino acids with a molecular mass of 45.8 kDa. The predicted pI is 4.96. It shows similarity to other endoglucanases from various fungi. From the comparison with other cellulase genes, cel2 belongs to family 7 of glucohydrolases. cel2 is located on a 2.5-Mb chromosome in C. carbonum and its expression is repressed by sucrose. A cel2 mutant of C. carbonum was created by transformation-mediated gene disruption. The pathogenicity of the mutant was indistinguishable from the wild type, indicating that cel2 by itself is not important for pathogenicity.
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Affiliation(s)
- J H Ahn
- Department of Forest Resource, Konkuk University, Seoul, Korea.
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Tsuchiya D, Taga M. Cytological Karyotyping of Three Cochliobolus spp. by the Germ Tube Burst Method. PHYTOPATHOLOGY 2001; 91:354-360. [PMID: 18943847 DOI: 10.1094/phyto.2001.91.4.354] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT Cytological karyotypes with mitotic metaphase chromosomes were analyzed for Cochliobolus heterostrophus, C. carbonum, and C. sativus by the germ tube burst method (GTBM). Prior to karyotyping, procedures of GTBM suitable to Cochliobolus were established by examining several crucial conditions such as incubation period of conidia. The estimated chromosome numbers of C. heterostrophus and C. carbonum were n = 15 or 16 and n = 13 or 15 depending on the strains, respectively. In C. sativus, n = 15 was estimated. Morphological information of chromosomes including chromosome size and a threadlike-specific structure representing the nucleolar organizing region was also obtained. Our results for some standard strains are in agreement with previous estimates by pulsed field gel electrophoresis (PFGE) or PFGE coupled with restriction fragment length polymorphism genetic linkage analysis, but inconsistent with the previous estimates for other strains by conventional light microscopic cytology. Additionally, PFGE analysis of C. heterostro-phus strains indicated that chromosome number was not determinable solely by PFGE, which is hampered by comigration and clumping of DNA bands.
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Applied mycology and biotechnology for agriculture and foods. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s1874-5334(01)80003-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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38
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Clustered metabolic pathway genes in filamentous fungi. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s1874-5334(01)80009-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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39
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Rosewich UL, Kistler HC. Role of Horizontal Gene Transfer in the Evolution of Fungi. ANNUAL REVIEW OF PHYTOPATHOLOGY 2000; 38:325-363. [PMID: 11701846 DOI: 10.1146/annurev.phyto.38.1.325] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Although evidence for horizontal gene transfer (HGT) in eukaryotes remains largely anecdotal, literature on HGT in fungi suggests that it may have been more important in the evolution of fungi than in other eukaryotes. Still, HGT in fungi has not been widely accepted because the mechanisms by which it may occur are unknown, because it is usually not directly observed but rather implied as an outcome, and because there are often equally plausible alternative explanations. Despite these reservations, HGT has been justifiably invoked for a variety of sequences including plasmids, introns, transposons, genes, gene clusters, and even whole chromosomes. In some instances HGT has also been confirmed under experimental conditions. It is this ability to address the phenomenon in an experimental setting that makes fungi well suited as model systems in which to study the mechanisms and consequences of HGT in eukaryotic organisms.
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Affiliation(s)
- U Liane Rosewich
- USDA-ARS Cereal Disease Laboratory, University of Minnesota, 1551 Lindig Street, St. Paul, Minnesota 55108; e-mail: ,
| | - H Corby Kistler
- USDA-ARS Cereal Disease Laboratory, University of Minnesota, 1551 Lindig Street, St. Paul, Minnesota 55108; e-mail: ,
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Daub ME, Ehrenshaft M. The Photoactivated Cercospora Toxin Cercosporin: Contributions to Plant Disease and Fundamental Biology. ANNUAL REVIEW OF PHYTOPATHOLOGY 2000; 38:461-490. [PMID: 11701851 DOI: 10.1146/annurev.phyto.38.1.461] [Citation(s) in RCA: 172] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Plant pathogenic fungi in eight genera produce light-activated perylenequinone toxins that are toxic to plants via the generation of activated oxygen species, particularly singlet oxygen. Studies on the cercosporin toxin produced by Cercospora species have documented an important role for this toxin in pathogenesis of host plants. Cercosporin-generated active oxygen species destroy the membranes of host plants, providing nutrients to support the growth of these intercellular pathogens. Resistance of Cercospora species to the toxic effects of their own toxin has allowed these organisms to be used as a model for understanding the cellular basis of resistance to singlet oxygen and to general oxidative stress. In particular, the recent discovery that pyridoxine (vitamin B6) quenches singlet oxygen has led to the understanding of a novel role for this vitamin in cells as well as the discovery of a novel pathway of biosynthesis.
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Affiliation(s)
- Margaret E Daub
- Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695-7616; e-mail:
| | - Marilyn Ehrenshaft
- Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695-7616; e-mail:
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41
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Tanaka A, Tsuge T. Structural and functional complexity of the genomic region controlling AK-toxin biosynthesis and pathogenicity in the Japanese pear pathotype of Alternaria alternata. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2000; 13:975-986. [PMID: 10975654 DOI: 10.1094/mpmi.2000.13.9.975] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The Japanese pear pathotype of Alternaria alternata produces host-specific AK-toxin and causes black spot of Japanese pear. Previously, a cosmid clone, pcAKT-1, was isolated that contains two genes, AKT1 and AKT2, within a 5.0-kb region required for AK-toxin biosynthesis. The wild-type strain has multiple, nonfunctional copies of these genes. In the present study, two additional genes, AKTR-1 and AKT3-1, downstream of AKT2 were identified. Transformation of the wild type with AKTR-1- and AKT3-1-targeting vectors produced toxin-deficient (Tox-), nonpathogenic mutants. DNA gel blot analysis, however, demonstrated that the fragments targeted in Tox- mutants were different from those containing AKTR-1 and AKT3-1 on the transforming vectors. A cosmid clone, pcAKT-2, containing the targeted DNA was isolated and shown to carry two genes, AKTR-2 and AKT3-2, with high similarity to AKTR-1 and AKT3-1, respectively. Transcripts from not only AKTR-2 and AKT3-2 but also AKTR-1 and AKT3-1 were found in the wild type. DNA gel blot analysis with pulsed-field gel electrophoresis showed that AKT1, AKT2, AKT3, and AKTR and their homologues are on a single chromosome. These results indicate the structural and functional complexity of the genomic region controlling AK-toxin biosynthesis.
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Affiliation(s)
- A Tanaka
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Japan
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Walton JD. Horizontal gene transfer and the evolution of secondary metabolite gene clusters in fungi: an hypothesis. Fungal Genet Biol 2000; 30:167-71. [PMID: 11035938 DOI: 10.1006/fgbi.2000.1224] [Citation(s) in RCA: 226] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- J D Walton
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
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Johnson RD, Johnson L, Itoh Y, Kodama M, Otani H, Kohmoto K. Cloning and characterization of a cyclic peptide synthetase gene from Alternaria alternata apple pathotype whose product is involved in AM-toxin synthesis and pathogenicity. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2000; 13:742-753. [PMID: 10875335 DOI: 10.1094/mpmi.2000.13.7.742] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Afternaria afternata apple pathotype causes Alternaria blotch of susceptible apple cultivars through the production of a cyclic peptide host-specific toxin, AM-toxin. PCR (polymerase chain reaction), with primers designed to conserved domains of peptide synthetase genes, amplified several products from A. alternata apple pathotype that showed high similarity to other fungal peptide synthetases and were specific to the apple pathotype. Screening of a Lambda Zap genomic library with these PCR-generated probes identified overlapping clones containing a complete cyclic peptide synthetase gene of 13.1 kb in length with no introns. Disruption of this gene, designated AM-toxin synthetase (AMT), by transformation of wild-type A. afternata apple pathotype with disruption vectors resulted in toxin-minus mutants, which were also unable to cause disease symptoms on susceptible apple cultivars. AM-toxin synthetase is therefore a primary determinant of virulence and specificity in the A. alternata apple pathotype/apple interaction.
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Affiliation(s)
- R D Johnson
- Laboratory of Plant Pathology, Faculty of Agriculture, Tottori University, Japan.
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Masunaka A, Tanaka A, Tsuge T, Peever TL, Timmer LW, Yamamoto M, Yamamoto H, Akimitsu K. Distribution and Characterization of AKT Homologs in the Tangerine Pathotype of Alternaria alternata. PHYTOPATHOLOGY 2000; 90:762-768. [PMID: 18944496 DOI: 10.1094/phyto.2000.90.7.762] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT The tangerine pathotype of Alternaria alternata produces a host-selective toxin (HST), known as ACT-toxin, and causes Alternaria brown spot disease of citrus. The structure of ACT-toxin is closely related to AK- and AF-toxins, which are HSTs produced by the Japanese pear and strawberry pathotypes of A. alternata, respectively. AC-, AK-, and AF-toxins are chemically similar and share a 9,10-epoxy-8-hydroxy-9-methyl-decatrienoic acid moiety. Two genes controlling AK-toxin biosynthesis (AKT1 and AKT2) were recently cloned from the Japanese pear pathotype of A. alternata. Portions of these genes were used as heterologous probes in Southern blots, that detected homologs in 13 isolates of A. alternata tangerine pathotype from Minneola tangelo in Florida. Partial sequencing of the homologs in one of these isolates demonstrated high sequence similarity to AKT1 (89.8%) and to AKT2 (90.7%). AKT homologs were not detected in nine isolates of A. alternata from rough lemon, six isolates of nonpathogenic A. alternata, and one isolate of A. citri that causes citrus black rot. The presence of homologs in the Minneola isolates and not in the rough lemon isolates, nonpathogens or black rot isolates, correlates perfectly to pathogenicity on Iyo tangerine and ACT-toxin production. Functionality of the homologs was demonstrated by detection of transcripts using reverse transcription-polymerase chain reaction (RT-PCR) in total RNA of the tangerine pathotype of A. alternata. The high sequence similarity of AKT and AKT homologs in the tangerine patho-type, combined with the structural similarity of AK-toxin and ACT-toxin, may indicate that these homologs are involved in the biosynthesis of the decatrienoic acid moiety of ACT-toxin.
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Wendland J, Ayad-Durieux Y, Knechtle P, Rebischung C, Philippsen P. PCR-based gene targeting in the filamentous fungus Ashbya gossypii. Gene 2000; 242:381-91. [PMID: 10721732 DOI: 10.1016/s0378-1119(99)00509-0] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We have investigated a PCR-based approach for one-step gene targeting in the filamentous fungus Ashbya gossypii. Short guide sequences with 40-46 bp of homology to two sequences of a targeted gene, provided by PCR, were sufficient to mediate homologous recombination. The PCR products used for transformation were generated from the newly constructed chimeric selection marker GEN3. This consists of the open reading frame of the Escherichia coli kanR gene under the control of promoter and terminator sequences of the Saccharomyces cerevisiae TEF2 gene and allows selection of G418/geneticin-resistant transformants. Verification of gene targeting was performed either by PCR or by DNA hybridization analyses, and in all 18 cases tested, correct targeting was confirmed. This approach was used for the complete deletion of the open reading frame of the A. gossypii RHO4 gene for which a double-strand sequence was available as information source for the design of PCR primers. We also demonstrated successful partial deletion of four other ORFs using single-read sequences (SRS) as sole information for the design of targeting primers. A gossypii is the first filamentous fungus in which a PCR-based gene disruption technique has been established. Since short target guide sequences are sufficient to direct homologous integration into the A. gossypii genome it is not necessary to obtain and sequence large DNA fragments from a target locus to provide the long flanking homology regions usually required for efficient targeting of cloned disruption cassettes in filamentous fungi. Thus functional analysis of A. gossypii genes is already possible, based on single-pass sequence information.
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Affiliation(s)
- J Wendland
- Lehrstuhl für Angewandte Microbiology, Biozentrum, University of Basel, Switzerland
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46
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Pitkin JW, Nikolskaya A, Ahn JH, Walton JD. Reduced virulence caused by meiotic instability of the TOX2 chromosome of the maize pathogen Cochliobolus carbonum. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2000; 13:80-87. [PMID: 10656588 DOI: 10.1094/mpmi.2000.13.1.80] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The mechanisms by which pathogenic fungi evolve are poorly understood. Production of the host-selective cyclic peptide HC-toxin is controlled by a complex locus, TOX2, in the plant pathogen Cochliobolus carbonum. Crosses between toxin-producing (Tox2+) and toxin-nonproducing (Tox2-) isolates, as well as crosses between isolates in which the TOX2 genes were on chromosomes of different size, yielded progeny that had lost one or more copies of one or more of the TOX2 genes. Of approximately 200 progeny analyzed, eight (4%) had lost at least one TOX2 gene. All of them still had at least one functional copy of all of the known genes required for HC-toxin production (HTS1, TOXA, TOXC, and TOXE). Most deletion strains could be explained by simple chromosome breaks resulting in the loss of major contiguous portions (0.8 to 1.4 Mb) of the 3.5-Mb TOX2 chromosome, whereas others had more complicated patterns. All deletion strains had normal growth and were fertile, indicating that the 1.4 Mb of DNA contained no essential housekeeping genes. Most strains were also still virulent (Tox2+), but two had a novel phenotype of reduced virulence (RV), characterized by smaller lesions that expanded at a reduced rate and an inability to colonize plants systemically. Although the RV strains made no detectable HC-toxin in culture, the RV phenotype was dependent on the presence of a functional copy of HTS1, which encodes the central enzyme in HC-toxin biosynthesis. We propose that the RV strains still make a low level of HC-toxin, at least in planta, and that this is due to the loss of one or more genes that contribute to, but are not absolutely required for, HC-toxin synthesis.
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Affiliation(s)
- J W Pitkin
- DOE-Plant Research Laboratory, Michigan State University, East Lansing 48824, USA
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Lee N, Bakkeren G, Wong K, Sherwood JE, Kronstad JW. The mating-type and pathogenicity locus of the fungus Ustilago hordei spans a 500-kb region. Proc Natl Acad Sci U S A 1999; 96:15026-31. [PMID: 10611332 PMCID: PMC24767 DOI: 10.1073/pnas.96.26.15026] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The fungal pathogen Ustilago hordei causes the covered smut disease of barley and oats. Mating and pathogenicity in this fungus are controlled by the MAT locus, which contains two distinct gene complexes, a and b. In this study, we tagged the a and b regions with the recognition sequence for the restriction enzyme I-SceI and determined that the distance between the complexes is 500 kb in a MAT-1 strain and 430 kb in a MAT-2 strain. Characterization of the organization of the known genes within the a and b gene complexes provided evidence for nonhomology and sequence inversion between MAT-1 and MAT-2. Antibiotic-resistance markers also were used to tag the a gene complex in MAT-1 strains (phleomycin) and the b gene complex in MAT-2 strains (hygromycin). Crosses were performed with these strains and progeny resistant to both antibiotics were recovered at a very low frequency, suggesting that recombination is suppressed within the MAT region. Overall, the chromosome homologues carrying the MAT locus of U. hordei share features with primitive sex chromosomes, with the added twist that the MAT locus also controls pathogenicity.
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Affiliation(s)
- N Lee
- Biotechnology Laboratory, Department of Microbiology University of British Columbia, Vancouver, BC, Canada V6T 1Z3
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Tanaka A, Shiotani H, Yamamoto M, Tsuge T. Insertional mutagenesis and cloning of the genes required for biosynthesis of the host-specific AK-toxin in the Japanese pear pathotype of Alternaria alternata. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 1999; 12:691-702. [PMID: 10432635 DOI: 10.1094/mpmi.1999.12.8.691] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The Japanese pear pathotype of Alternaria alternata causes black spot of Japanese pear by producing a host-specific toxin known as AK-toxin. Restriction enzyme-mediated integration (REMI) mutagenesis was used to tag genes required for toxin biosynthesis. Protoplasts of a wild-type strain were treated with a linearized plasmid along with the restriction enzyme used to linearize the plasmid. Of 984 REMI transformants recovered, three produced no detectable AK-toxin and lost pathogenicity on pear leaves. Genomic DNA flanking the integrated plasmid was recovered from one of the mutants. With the recovered DNA used as a probe, a cosmid clone of the wild-type strain was isolated. Structural and functional analyses of an 8.0-kb region corresponding to the tagged site indicated the presence of two genes. One, designated AKT1, encodes a member of the class of carboxyl-activating enzymes. The other, AKT2, encodes a protein of unknown function. The essential roles of these two genes in both AK-toxin production and pathogenicity were confirmed by transformation-mediated gene disruption experiments. DNA gel blot analysis detected AKT1 and AKT2 homologues not only in the Japanese pear pathotype strains but also in strains from the tangerine and strawberry pathotypes. The host-specific toxins of these two pathotypes are similar in structure to AK-toxin. Homologues were not detected in other pathotypes or in non-pathogenic strains of A. alternata, suggesting acquisition of AKT1 and AKT2 by horizontal transfer.
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Affiliation(s)
- A Tanaka
- Graduate School of Bioagricultural Sciences, Nagoya University, Japan
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Abstract
In this review the organization of fungal chromosomes and the methods used for karyotype analysis are briefly summarized. The role of chromosome rearrangement, supernumerary chromosomes and repeated DNA sequences in the genetic change of fungi is evaluated.
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Affiliation(s)
- L Hornok
- Agricultural Biotechnology Center, Gödölló, Hungary
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50
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Scott-Craig JS, Cheng YQ, Cervone F, De Lorenzo G, Pitkin JW, Walton JD. Targeted mutants of Cochliobolus carbonum lacking the two major extracellular polygalacturonases. Appl Environ Microbiol 1998; 64:1497-503. [PMID: 9546185 PMCID: PMC106176 DOI: 10.1128/aem.64.4.1497-1503.1998] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The filamentous fungus Cochliobolus carbonum produces endo-alpha 1,4-polygalacturonase (endoPG), exo-alpha 1,4-polygalacturonase (exoPG), and pectin methylesterase when grown in culture on pectin. Residual activity in a pgn1 mutant (lacking endoPG) was due to exoPG activity, and the responsible protein has now been purified. After chemical deglycosylation, the molecular mass of the purified protein decreased from greater than 60 to 45 kDa. The gene that encodes exoPG, PGX1, was isolated with PCR primers based on peptide sequences from the protein. The product of PGX1, Pgx1p, has a predicted molecular mass of 48 kDa, 12 potential N-glycosylation sites, and 61% amino acid identity to an exoPG from the saprophytic fungus Aspergillus tubingensis. Strains of C. carbonum mutated in PGX1 were constructed by targeted gene disruption and by gene replacement. Growth of pgx1 mutant strains on pectin was reduced by ca. 20%, and they were still pathogenic on maize. A double pgn1/pgx1 mutant strain was constructed by crossing. The double mutant grew as well as the pgx1 single mutant on pectin and was still pathogenic despite having less than 1% of total wild-type PG activity. Double mutants retained a small amount of PG activity with the same cation-exchange retention time as Pgn1p and also pectin methylesterase and a PG activity associated with the mycelium. Continued growth of the pgn1/pgx1 mutant on pectin could be due to one or more of these residual activities.
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Affiliation(s)
- J S Scott-Craig
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing 48824, USA
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