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Exploring a novel genomic safe-haven site in the human pathogenic mould Aspergillus fumigatus. Fungal Genet Biol 2022; 161:103702. [PMID: 35569804 DOI: 10.1016/j.fgb.2022.103702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 05/04/2022] [Accepted: 05/07/2022] [Indexed: 11/24/2022]
Abstract
Aspergillus fumigatus is the most important airborne fungal pathogen and allergen of humans causing high morbidity and mortality worldwide. The factors that govern pathogenicity of this organism are multi-factorial and are poorly understood. Molecular tools to dissect the mechanisms of pathogenicity in A. fumigatus have improved significantly over the last 20 years however many procedures have not been standardised for A. fumigatus. Here, we present a new genomic safe-haven locus at the site of an inactivated transposon, named SH-aft4, which can be used to insert DNA sequences in the genome of this fungus without impacting its phenotype. We show that we are able to effectively express a transgene construct from the SH-aft4 and that natural regulation of promoter function is conserved at this site. Furthermore, the SH-aft4 locus is highly conserved in the genome of a wide range of clinical and environmental isolates including the isolates commonly used by many laboratories CEA10, Af293 and ATCC46645, allowing a wide range of isolates to be manipulated. Our results show that the aft4 locus can serve as a site for integration of a wide range of genetic constructs to aid functional genomics studies of this important human fungal pathogen.
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Evangelinos M, Anagnostopoulos G, Karvela-Kalogeraki I, Stathopoulou PM, Scazzocchio C, Diallinas G. Minos as a novel Tc1/mariner-type transposable element for functional genomic analysis in Aspergillus nidulans. Fungal Genet Biol 2015; 81:1-11. [PMID: 26021704 DOI: 10.1016/j.fgb.2015.05.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 05/15/2015] [Accepted: 05/18/2015] [Indexed: 10/23/2022]
Abstract
Transposons constitute powerful genetic tools for gene inactivation, exon or promoter trapping and genome analyses. The Minos element from Drosophila hydei, a Tc1/mariner-like transposon, has proved as a very efficient tool for heterologous transposition in several metazoa. In filamentous fungi, only a handful of fungal-specific transposable elements have been exploited as genetic tools, with the impala Tc1/mariner element from Fusarium oxysporum being the most successful. Here, we developed a two-component transposition system to manipulate Minos transposition in Aspergillus nidulans (AnMinos). Our system allows direct selection of transposition events based on re-activation of niaD, a gene necessary for growth on nitrate as a nitrogen source. On average, among 10(8) conidiospores, we obtain up to ∼0.8×10(2) transposition events leading to the expected revertant phenotype (niaD(+)), while ∼16% of excision events lead to AnMinos loss. Characterized excision footprints consisted of the four terminal bases of the transposon flanked by the TA target duplication and led to no major DNA rearrangements. AnMinos transposition depends on the presence of its homologous transposase. Its frequency was not significantly affected by temperature, UV irradiation or the transcription status of the original integration locus (niaD). Importantly, transposition is dependent on nkuA, encoding an enzyme essential for non-homologous end joining of DNA in double-strand break repair. AnMinos proved to be an efficient tool for functional analysis as it seems to transpose in different genomic loci positions in all chromosomes, including a high proportion of integration events within or close to genes. We have used Minos to obtain morphological and toxic analogue resistant mutants. Interestingly, among morphological mutants some seem to be due to Minos-elicited over-expression of specific genes, rather than gene inactivation.
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Affiliation(s)
- Minoas Evangelinos
- Faculty of Biology, University of Athens, Panepistimioupolis, Athens 15784, Greece
| | | | | | | | - Claudio Scazzocchio
- Department of Microbiology, Imperial College London, London SW7 2AZ, United Kingdom; Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Bâtiment 400, 91405 Orsay Cedex, France
| | - George Diallinas
- Faculty of Biology, University of Athens, Panepistimioupolis, Athens 15784, Greece.
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Nogueira GB, Queiroz MV, Ribeiro RA, Araújo EF. Structural and functional characterization of the Colletotrichum lindemuthianum nit1 gene, which encodes a nitrate eductase enzyme. GENETICS AND MOLECULAR RESEARCH 2013; 12:420-33. [PMID: 23420367 DOI: 10.4238/2013.february.8.7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Colletotrichum lindemuthianum is the causal agent of plant bean anthracnose, one of the most important diseases affecting the common bean. We investigated the structure and expression of the nit1 gene (nitrate reductase) of C. lindemuthianum. The nit1 gene open reading frame contains 2787 bp, interrupted by a single 69-bp intron. The predicted protein has 905 amino acids; it shows high identity with the nitrate reductase of C. higginsianum (79%) and C. graminicola (73%). Expression of nit1 in C. lindemuthianum was evaluated in mycelia grown on different nitrogen sources under conditions of activation and repression. The gene was expressed after 15 min of induction with nitrate, reaching maximum expression at 360 min. The transcription was repressed in mycelia grown in media enriched with ammonia, urea or glutamine. Twenty nit1⁻ mutants were obtained in a medium treated with chlorate. Ten of these mutants were characterized by DNA hybridization, which identified point mutations, a deletion and an insertion. These rearrangements in the nit1 gene in the different mutants may have occurred through activity of transposable elements.
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Affiliation(s)
- G B Nogueira
- Departamento de Microbiologia, Instituto de Biotecnologia Aplicada à Agropecuária, Universidade Federal de Viçosa, Viçosa, MG, Brasil
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Sato A, Oshima K, Noguchi H, Ogawa M, Takahashi T, Oguma T, Koyama Y, Itoh T, Hattori M, Hanya Y. Draft genome sequencing and comparative analysis of Aspergillus sojae NBRC4239. DNA Res 2011; 18:165-76. [PMID: 21659486 PMCID: PMC3111232 DOI: 10.1093/dnares/dsr009] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We conducted genome sequencing of the filamentous fungus Aspergillus sojae NBRC4239 isolated from the koji used to prepare Japanese soy sauce. We used the 454 pyrosequencing technology and investigated the genome with respect to enzymes and secondary metabolites in comparison with other Aspergilli sequenced. Assembly of 454 reads generated a non-redundant sequence of 39.5-Mb possessing 13 033 putative genes and 65 scaffolds composed of 557 contigs. Of the 2847 open reading frames with Pfam domain scores of >150 found in A. sojae NBRC4239, 81.7% had a high degree of similarity with the genes of A. oryzae. Comparative analysis identified serine carboxypeptidase and aspartic protease genes unique to A. sojae NBRC4239. While A. oryzae possessed three copies of α-amyalse gene, A. sojae NBRC4239 possessed only a single copy. Comparison of 56 gene clusters for secondary metabolites between A. sojae NBRC4239 and A. oryzae revealed that 24 clusters were conserved, whereas 32 clusters differed between them that included a deletion of 18 508 bp containing mfs1, mao1, dmaT, and pks-nrps for the cyclopiazonic acid (CPA) biosynthesis, explaining the no productivity of CPA in A. sojae. The A. sojae NBRC4239 genome data will be useful to characterize functional features of the koji moulds used in Japanese industries.
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Affiliation(s)
- Atsushi Sato
- Research and Development Division, Kikkoman Corporation, 399 Noda, Noda City, Chiba 278-0037, Japan
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Ogasawara H, Obata H, Hata Y, Takahashi S, Gomi K. Crawler, a novel Tc1/mariner-type transposable element in Aspergillus oryzae transposes under stress conditions. Fungal Genet Biol 2009; 46:441-9. [DOI: 10.1016/j.fgb.2009.02.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Revised: 02/16/2009] [Accepted: 02/23/2009] [Indexed: 10/21/2022]
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Cecília de Lima Fávaro L, Luiz Araújo W, Aparecida de Souza-Paccola E, Lúcio Azevedo J, Paccola-Meirelles LD. Colletotrichum sublineolum genetic instability assessed by mutants resistant to chlorate. ACTA ACUST UNITED AC 2006; 111:93-105. [PMID: 17158042 DOI: 10.1016/j.mycres.2006.08.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Revised: 05/26/2006] [Accepted: 08/30/2006] [Indexed: 11/28/2022]
Abstract
The fungus Colletotrichum sublineolum, causal agent of sorghum anthracnose, presents high variability, genetic instability and host specialization. The aims of the present work were to investigate the mechanisms involved in the genetic instability in this species. Mutants resistant to chlorate and unable to use nitrate (Nit mutants), were obtained spontaneously, isolated and characterized for complementation pattern, reversion frequency and RAPD profile. The results showed that chlorate-resistant mutants could be divided into six phenotypic classes that probably represented mutations in the structural nitrate reductase locus (nit1), in the structural nitrite reductase locus (nit6 and niiA of Neurospora and Aspergillus, respectively), in the specific regulator locus (nit3), in the main regulator locus (nit2), in loci that codified the cofactor containing molybdenum necessary for nitrate reductase activity (NitM), and one or more genes responsible for nitrate intake (crn). In addition, the genetic control of this metabolism in C. sublineolum seems to be similar to other fungi species such as Aspergillus, Neurospora and Fusarium. The high reversion frequency (10(-4) to 10(-5)) presented by nit1 mutants suggests that the instability in evaluated strains could be a result of transposable elements activity. The RAPD analysis enabled confirmation that the Nit mutants have a similar genetic background to original strain, and that polymorphism exists among wild-type strains, nit1 mutants and revertants of C. sublineolum. These are important aspects for the later direction of molecular analysis, where these mutants will be used as a tool to isolate the active transposable elements in the C. sublineolum genome.
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Affiliation(s)
- Léia Cecília de Lima Fávaro
- Universidade de São Paulo, Escola Superior de Agricultura Luiz de Queiroz, Departamento de Genética, PO Box 83, 13400-970 Piracicaba, São Paulo, Brazil.
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Montiel MD, Lee HA, Archer DB. Evidence of RIP (repeat-induced point mutation) in transposase sequences of Aspergillus oryzae. Fungal Genet Biol 2006; 43:439-45. [PMID: 16531081 DOI: 10.1016/j.fgb.2006.01.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2005] [Revised: 01/06/2006] [Accepted: 01/26/2006] [Indexed: 11/20/2022]
Abstract
A DNA methyl-binding column was used to isolate genomic fragments enriched for DNA-methylation from Aspergillus parasiticus. One of the isolated sequences presented 67% identity at the protein level with the transposase from the transposable element Tan1 of Aspergillus niger var. awamori, and was found to be present in at least 20 copies in the Aspergillus oryzae database. Analysis of four copies showed evidence of C:G to T:A transitions in at least 98.2% of the mutations found over a 1,032-1,180 bp region spanning a large part of the transposase sequence. Using copy specific primers three sequences were amplified from a different strain of A. oryzae and a similar pattern of C:G to T:A transitions was found. These transitions are similar to those observed in RIP, in Neurospora crassa, where cytosine-methylation is believed to be involved. Using methylation-sensitive Southern blotting, no evidence of methylation was found in the transposase sequences in these two A. oryzae strains as well as one A. parasiticus and one Aspergillus flavus strain.
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Affiliation(s)
- Maria D Montiel
- Institute of Genetics, School of Biology, University of Nottingham, University Park, Nottingham NG7 2RD, UK
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Fávaro LCDL, Araújo WLD, Azevedo JLD, Paccola-Meirelles LD. The biology and potential for genetic research of transposable elements in filamentous fungi. Genet Mol Biol 2005. [DOI: 10.1590/s1415-47572005000500024] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Monroy F, Sheppard DC. Taf1: a class II transposon of Aspergillus fumigatus. Fungal Genet Biol 2005; 42:638-45. [PMID: 15896988 DOI: 10.1016/j.fgb.2005.04.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Revised: 03/29/2005] [Accepted: 04/02/2005] [Indexed: 12/01/2022]
Abstract
Aspergillus fumigatus is an important medical pathogen that lacks a known sexual cycle. Transposons may provide an important mechanism for the generation of genetic diversity in this organism. Here, we describe Taf1, the first class II transposon to be identified in A. fumigatus. Taf1, a member of the mariner superfamily and pogo family of transposons, is distinguished by the presence of extremely long (89 bp) inverted repeats that flank the transposase coding sequence. Taf1 is present in different locations and copy number among clinical strains of A. fumigatus and is transcribed. Analysis of multiple insertion sequences within a single strain suggests that Taf1 elements undergo inactivation by a repeat induced polymorphism-like mechanism. Taf1 insertion patterns were extremely stable despite multiple stressors including heat shock, serial passage, and infection in mice. Thus Taf1 may be useful for strain identification and molecular typing.
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Affiliation(s)
- Franz Monroy
- Division of Infectious Diseases, Department of Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA
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Pritham EJ, Feschotte C, Wessler SR. Unexpected Diversity and Differential Success of DNA Transposons in Four Species of Entamoeba Protozoans. Mol Biol Evol 2005; 22:1751-63. [PMID: 15901838 DOI: 10.1093/molbev/msi169] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We report the first comprehensive analysis of transposable element content in the compact genomes (approximately 20 Mb) of four species of Entamoeba unicellular protozoans for which draft sequences are now available. Entamoeba histolytica and Entamoeba dispar, two human parasites, have many retrotransposons, but few DNA transposons. In contrast, the reptile parasite Entamoeba invadens and the free-living Entamoeba moshkovskii contain few long interspersed elements but harbor diverse and recently amplified populations of DNA transposons. Representatives of three DNA transposase superfamilies (hobo/Activator/Tam3, Mutator, and piggyBac) were identified for the first time in a protozoan species in addition to a variety of members of a fourth superfamily (Tc1/mariner), previously reported only from ciliates and Trichomonas vaginalis among protozoans. The diversity of DNA transposons and their differential amplification among closely related species with similar compact genomes are discussed in the context of the biology of Entamoeba protozoans.
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Affiliation(s)
- Ellen J Pritham
- Department of Plant Biology, The University of Georgia, USA.
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Li Destri Nicosia MG, Brocard-Masson C, Demais S, Hua Van A, Daboussi MJ, Scazzocchio C. Heterologous transposition in Aspergillus nidulans. Mol Microbiol 2004. [DOI: 10.1111/j.1365-2958.2001.02323.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Abstract
The past 10 years have been productive in the characterization of fungal transposable elements (TEs). All eukaryotic TEs described are found including an extraordinary prevalence of active members of the pogo family. The role of TEs in mutation and genome organization is well documented, leading to significant advances in our perception of the mechanisms underlying genetic changes in these organisms. TE-mediated changes, associated with transposition and recombination, provide a broad range of genetic variation, which is useful for natural populations in their adaptation to environmental constraints, especially for those lacking the sexual stage. Interestingly, some fungal species have evolved distinct silencing mechanisms that are regarded as host defense systems against TEs. The examination of forces acting on the evolutionary dynamics of TEs should provide important insights into the interactions between TEs and the fungal genome. Another issue of major significance is the practical applications of TEs in gene tagging and population analysis, which will undoubtedly facilitate research in systematic biology and functional genomics.
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Affiliation(s)
- Marie-Josée Daboussi
- Institut de Génétique et Microbiologie, Université Paris-Sud, F-91405 Orsay cedex, France.
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Okubara PA, Tibbot BK, Tarun AS, McAlpin CE, Hua SST. Partial retrotransposon-like DNA sequence in the genomic clone of Aspergillus flavus, pAF28. MYCOLOGICAL RESEARCH 2003; 107:841-6. [PMID: 12967211 DOI: 10.1017/s0953756203008116] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A genomic clone of the aflatoxin-producing fungus Aspergillus flavus, designated pAF28, has been used as a probe for Southern blot fingerprinting of fungal strains. A large number of A. flavus strains isolated from corn fields and tree-nut orchards can be distinguished because the DNA fingerprint patterns are highly polymorphic. We have completed the sequencing of a 6355 bp insert in pAF28. The sequence features motifs and open reading frames characteristic of transposable elements of the gypsy class. We have named this new element AfRTL-1, for A. flavus retrotransposon-like DNA.
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Affiliation(s)
- Patricia A Okubara
- USDA, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA 94710, USA
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Ladendorf O, Brachmann A, Kämper J. Heterologous transposition in Ustilago maydis. Mol Genet Genomics 2003; 269:395-405. [PMID: 12734750 DOI: 10.1007/s00438-003-0848-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2002] [Accepted: 03/31/2003] [Indexed: 11/25/2022]
Abstract
The phytopathogenic basidiomycete Ustilago maydis has become a model system for the analysis of plant-pathogen interactions. The genome sequence of this organism will soon be available, increasing the need for techniques to analyse gene function on a broad basis. We describe a heterologous transposition system for U. maydis that is based on the Caenorhabditis transposon Tc1, which is known to function independently of host factors and to be active in evolutionarily distant species. We have established a nitrate reductase based two-component counterselection system to screen for Tc1 transposition. The element was shown to be functional and transposed to several different locations in the genome of U. maydis. The insertion pattern observed was consistent with the proposed general mechanism of Tc1/mariner integration and constitutes a proof of principle for the first heterologous transposition system in a basidiomycete species. By mapping the insertion site context to known genomic sequences, Tc1 insertion events were shown to occur on different chromosomes, but exhibit a preference for non-coding regions. Only 20% of the insertions were found in putative open reading frames. The establishment of this system will permit efficient gene tagging in U. maydis and possibly also in other fungi.
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Affiliation(s)
- O Ladendorf
- Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch Str., 35043 Marburg, Germany
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Daboussi MJ, Davière JM, Graziani S, Langin T. Evolution of the Fot1 transposons in the genus Fusarium: discontinuous distribution and epigenetic inactivation. Mol Biol Evol 2002; 19:510-20. [PMID: 11919292 DOI: 10.1093/oxfordjournals.molbev.a004106] [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: 11/14/2022] Open
Abstract
To understand the evolution of Fot1, a member of the pogo family widely dispersed in ascomycetes, we have performed a phylogenetic survey across the genus Fusarium divided into six sections. The taxonomic distribution of Fot1 is not homogeneous but patchy; it is prevalent in the Fusarium oxysporum complex, absent in closely related sections, and found in five species from the most distant section Martiella. Multiple copies of Fot1 were sequenced from each strain in which the element occurs. In three species, the Fot1 nucleotide sequence is 98% identical to that from F. oxysporum (Fox), whereas nucleotide divergence for host genes is markedly higher: 11% for partial nuclear 28S rDNA and up to 30% for the gene encoding nitrate reductase (nia). In two species, sequence divergence of Fot1-related elements relative to Fox ranged from 7% to 23% (16% average). Most of the sequence differences (82%) were C-to-T and G-to-A transitions. These mutations are distributed throughout the Fot1 sequences, although they tend to be concentrated in the middle portion of the elements. Analysis of the local sequence context of transitions revealed a hierarchy of site preferences. These characteristics are typical of the repeat-induced point mutation process, first discovered in Neurospora crassa. The spotty distribution of Fot1 elements among species together with the high degree of similarity between Fot1 sequences present in distant species strongly suggests a case of horizontal transfer.
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Affiliation(s)
- Marie-Josée Daboussi
- Institut de Génétique et Microbiologie, Bât 400, Université Paris-Sud, 91405 Orsay, France.
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Abstract
DNA from Aspergillus sp. has been reported not to contain 5-methylcytosine. However, it has been found that Aspergillus nidulans responds to 5-azacytidine, a drug that is a strong inhibitor of DNA methyltransferases. Therefore, we have re-examined the occurrence of 5-methylcytosine in DNA from Aspergillus flavus by using a highly sensitive and specific method for detection of modified bases in genomic DNA comprising high-performance liquid chromatography separation of nucleosides, labeling of the nucleoside with deoxynucleoside kinase and two-dimensional thin-layer chromatography. Our results show that 5-methylcytosine is present in DNA from A. flavus. We estimate the relative amounts of 5-methylcytosine to cytosine to be approximately 1/400.
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Affiliation(s)
- H Gowher
- Institut für Biochemie, FB 8, Heinrich-Buff-Ring 58, 3392 Giessen, Germany
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Abstract
Manipulation of the genome of the human pathogen Aspergillus fumigatus is not well developed. Approaches and data from related model organisms are being used to develop molecular genetic systems in A. fumigatus; for example, the molecular typing of strains during infection. A genome-sequencing programme has begun and will form the basis for future development.
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Affiliation(s)
- J L Brookman
- School of Biological Sciences, University of Manchester, 1.800 Stopford Building, Oxford Road, M13 9PT, Manchester, UK.
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Capy P, Gasperi G, Biémont C, Bazin C. Stress and transposable elements: co-evolution or useful parasites? Heredity (Edinb) 2000; 85 ( Pt 2):101-6. [PMID: 11012710 DOI: 10.1046/j.1365-2540.2000.00751.x] [Citation(s) in RCA: 282] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The activity of transposable elements can be induced by environmental and population factors and in particular by stresses in various organisms. A consequence of the increase in transposable element mobility is the creation of new genetic variability that can be useful in the face of stressful conditions. In this review, results supporting this hypothesis are presented and discussed. The main question is how stress induces the activity of transposable elements. We discuss hypotheses based upon the existence of promoters or fixation sites of transcription activators in the untranslated regions of transposable elements, similar to those found in regulatory regions of host defence genes.
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Affiliation(s)
- P Capy
- Laboratoire Populations, Génétique et Evolution, CNRS - UPR 9034, 91198 Gif-sur-Yvette Cedex, France.
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Sonnenberg AS, Baars JJ, Mikosch TS, Schaap PJ, Van Griensven LJ. Abr1, a transposon-like element in the genome of the cultivated mushroom Agaricus bisporus (Lange) Imbach. Appl Environ Microbiol 1999; 65:3347-53. [PMID: 10427018 PMCID: PMC91503 DOI: 10.1128/aem.65.8.3347-3353.1999] [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] [Received: 01/08/1999] [Accepted: 06/03/1999] [Indexed: 11/20/2022] Open
Abstract
A 300-bp repetitive element was found in the genome of the white button mushroom, Agaricus bisporus, and designated Abr1. It is present in approximately 15 copies per haploid genome in the commercial strain Horst U1. Analysis of seven copies showed 89 to 97% sequence identity. The repeat has features typical of class II transposons (i.e., terminal inverted repeats, subterminal repeats, and a target site duplication of 7 bp). The latter shows a consensus sequence. When used as probe on Southern blots, Abr1 identifies relatively little variation within traditional and present-day commercial strains, indicating that most strains are identical or have a common origin. In contrast to these cultivars, high variation is found among field-collected strains. Furthermore, a remarkable difference in copy numbers of Abr1 was found between A. bisporus isolates with a secondarily homothallic life cycle and those with a heterothallic life cycle. Abr1 is a type II transposon not previously reported in basidiomycetes and appears to be useful for the identification of strains within the species A. bisporus.
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Affiliation(s)
- A S Sonnenberg
- Mushroom Experimental Station, NL-5960 AA Horst, The Netherlands.
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Gómez-Gómez E, Anaya N, Roncero MI, Hera C. Folyt1, a new member of the hAT family, is active in the genome of the plant pathogen Fusarium oxysporum. Fungal Genet Biol 1999; 27:67-76. [PMID: 10413616 DOI: 10.1006/fgbi.1999.1132] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An active transposable element, Folyt1, has been isolated from the tomato pathogen Fusarium oxysporum f. sp. lycopersici as an insertion sequence within the coding region of the nitrate reductase gene (nit 1) in two independent mutants (CO66 and CO108). Folyt1 was 2615 bp in length and contained 9-bp imperfect inverted terminal repeats (ITRs) and 8 bp duplicated at the target site upon insertion. The element contained a long open reading frame interrupted by a single putative intron. The predicted amino acid sequence showed similarity to conserved domains of transposases from hobo, Ac, and Tam3 elements, which belong to the hAT family. The excision frequency of Folyt1 was determined to be less than 10(-5) in both mutants. These events restored the nit 1 wild-type allele without leaving footprints in all the revertants of strain CO66. Nevertheless, some revertants of strain CO108 showed a point mutation footprint at the target sequence. Expression of the Folyt1 transposase was detected by Northern analysis as a 2.1-kb transcript. The element exists in about 10 copies per genome in F. oxysporum f. sp. lycopersici and appears to be widely distributed among different formae speciales of F. oxysporum.
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Affiliation(s)
- E Gómez-Gómez
- Departamento de Genética, Facultad de Ciencias, Córdoba, Spain
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Abstract
Transposons are ubiquitous genetic elements discovered so far in all investigated prokaryotes and eukaryotes. In remarkable contrast to all other genes, transposable elements are able to move to new locations within their host genomes. Transposition of transposons into coding sequences and their initiation of chromosome rearrangements have tremendous impact on gene expression and genome evolution. While transposons have long been known in bacteria, plants, and animals, only in recent years has there been a significant increase in the number of transposable elements discovered in filamentous fungi. Like those of other eukaryotes, each fungal transposable element is either of class or of class II. While class I elements transpose by a RNA intermediate and employ reverse transcriptases, class II elements transpose directly at the DNA level. We present structural and functional features for such transposons that have been identified so far in filamentous fungi. Emphasis is given to specific advantages or unique features when fungal systems are used to study transposable elements, e.g., the evolutionary impact of transposons in coenocytic organisms and possible experimental approaches toward horizontal gene transfer. Finally, we focus on the potential of transposons for tagging and identifying fungal genes.
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Affiliation(s)
- F Kempken
- Lehrstuhl für Allgemeine Botanik, Ruhr-Universität Bochum, Germany
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22
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Abstract
Integration of retroposed RNA in mammals occurs at staggered breaks resulting from an enzyme-generated pair of nicks at opposite DNA strands, preferably within 15-16 bp. Although consensus sequences associated with the two nicks appear somewhat different from one another, both nicking sites are rich in TA, CA and TG dinucleotide steps which are known as specific DNA sites where kinks may occur under bending constraints. This suggests that during interaction with the endonucleolytic enzyme, or enzymes, DNA undergoes bending at the integration sites and kinks are formed, as initial steps in generating the nicks. Nicking at kinkable sites, particularly at TA steps, may also play a role in integration of other insertion elements.
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Affiliation(s)
- J Jurka
- Genetic Information Research Institute, Palo Alto, CA 94306, USA.
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Enkerli J, Bhatt G, Covert SF. Nht1, a transposable element cloned from a dispensable chromosome in Nectria haematococca. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 1997; 10:742-9. [PMID: 9245836 DOI: 10.1094/mpmi.1997.10.6.742] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Certain isolates of the plant-pathogenic fungus Nectria haematococca mating population VI (MPVI) contain dispensable chromosomes that are unstable during sexual reproduction. Several of these chromosomes carry genes for phytoalexin detoxification and thus contribute to the pathogenic potential of this organism. A repeated DNA sequence, Nht1, was cloned from one of these dispensable chromosomes in N. haematococca MPVI. One copy of the repeated element (Nht1A) was completely sequenced. It is 2,198 bp long and it possesses incomplete inverted terminal repeats (ITRs) at each end. Nht1B, a partially sequenced copy of Nht1, has complete ITRs. Nht1A appears to contain 2 introns and encodes a protein of 550 amino acids that is highly similar to the protein encoded by the Fusarium oxysporum transposon, Fot1. Due to the presence of ITRs, its repeated nature, and its similarity to Fot1, we conclude that Nht1 is a transposable element. Within North American N. Haematococca MPVI populations, Nht1 is distributed discontinuously. Its copy number in different field isolates varies from zero to approximately 100 copies per genome. The Nht1A source isolate is estimated to contain nine to 11 copies of Nht1; at least six are on the chromosome from which Nht1A was cloned.
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Affiliation(s)
- J Enkerli
- Department of Botany, University of Georgia, Athens 30602, USA
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27
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Kempken F, Kück U. restless, an active Ac-like transposon from the fungus Tolypocladium inflatum: structure, expression, and alternative RNA splicing. Mol Cell Biol 1996; 16:6563-72. [PMID: 8887685 PMCID: PMC231658 DOI: 10.1128/mcb.16.11.6563] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Elements of the hAT transposon family, such as the maize activator (Ac), have been discovered in a large number of eukaryotic species. This type of class II transposon, present in both plants and animals, has not been previously detected in any fungal organism. However, using a differential screening method to detect repetitive DNA, we have identified a hAT transposon in the hyphomycete Tolypocladium inflatum. The transposon, which we named restless, is 4,097 bp long, carries 20-bp inverted repeats and an 8-bp target site duplication, and encodes a long open reading frame which is interrupted by a single intronic sequence. The derived mRNA exhibits alternative splicing, resulting in the formation of two transcripts that may be translated into polypeptides of 157 or 803 amino acids. The predicted amino acid sequence of the larger polypeptide demonstrates significant homology with transposases from the hAT transposon family. A chromosomal analysis using pulsed-field gel electrophoresis showed that all seven chromosomal bands carry copies of the 4.1-kb transposon. This was confirmed in hybridization experiments with rare-cutting restriction endonucleases which indicate that about 15 copies are present in T. inflatum. The genomic distribution of restless and its transcriptional expression, alternative mRNA splicing, and genomic mobility all imply a potential role for this element in developing a transposon tagging system for use in filamentous fungi.
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Affiliation(s)
- F Kempken
- Lehrstuhl für Allgemeine Botanik, Ruhr-Universität Bochum, Germany
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28
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Abstract
The fungus Phycomyces blakesleeanus has a relatively small genome, 30 megabases (Mb), with a low guanine and cytosine (G + C) content, 35%; the coding sequences cloned to date all have a G + C content of about 50%. In order to investigate the organization of the genome of this fungus, we have cloned and sequenced 251 DNA fragments. One hundred and twenty-six clones were obtained by digestion with MspI (target sequence 5'-CCGG-3') and 125 random clones were obtained by sonication. The average length of sequence obtained was about 200 base pairs (bp) and the total length was about 50 kilobases (kb). The G + C content is not homogeneous throughout the genome: sequences obtained after digestion with MspI have an average of 5% more G + C content than the random fragments, and are enriched in coding sequences. Fourteen MspI fragments show similarities to known proteins and 21 encode ribosomal RNA (rRNA). By contrast, only three of the random fragments are similar to known proteins and only one to a rRNA. We conclude that the Phycomyces genome is composed of G + C-rich genes surrounded by G + C-poor areas. Two clones have similarities to the transposase of the transposon Tc1 from Caenorhabditis elegans. This result suggests the presence of a high copy number of a Tc1-like transposable element in the Phycomyces genome. Another clone was similar to the transposon Tx1 from Xenopus laevis. A novel repetitive nt sequence has been characterized; about 5% of the total genome is a repetition of any of two consensus sequences of 31 bp named PrA1 and PrA2.
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Affiliation(s)
- J Avalos
- Department of Medicine, University of Cambridge School of Clinical Medicine, UK.
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Robertson HM, Asplund ML. Bmmar1: a basal lineage of the mariner family of transposable elements in the silkworm moth, Bombyx mori. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 1996; 26:945-954. [PMID: 9014339 DOI: 10.1016/s0965-1748(96)00061-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We describe a transposable element, called Bmmar1, from the genome of the silkworm moth, Bombyx mori. This element has features of the Tc1-mariner superfamily of transposable elements. Bmmar1 was first detected as a fragment in the 5' region of the larval serum protein (BmLSP) gene. Six genomic clones characterized each differed from a consensus sequence by 3-5 insertions and deletions, as well as an average of 2.3% in nucleotide sequence. The genome contains approximately 2400 copies of Bmmar1. Maximum parsimony phylogenetic analysis of the relationship of Bmmar1 and other members of the Tc1-mariner superfamily, based on their encoded transposase amino acid sequences, indicates that it represents a basal lineage of the mariner family. In particular Bmmar1 encodes a D,D37D motif thought to be the catalytic domain of mariner transposases. Bmmar1 considerably increases the known diversity of this widespread family of transposons. A new naming system is proposed for members of the family.
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Affiliation(s)
- H M Robertson
- Department of Entomology, University of Illinos, Urbana 61801, USA.
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