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Abstract
Fungi are prone to phenotypic instability, that is, the vegetative phase of these organisms, be they yeasts or molds, undergoes frequent switching between two or more behaviors, often with different morphologies, but also sometime having different physiologies without any obvious morphological outcome. In the context of industrial utilization of fungi, this can have a negative impact on the maintenance of strains and/or on their productivity. Instabilities have been shown to result from various mechanisms, either genetic or epigenetic. This chapter will review different types of instabilities and discuss some lesser-known ones, mostly in filamentous fungi, while it will direct readers to additional literature in the case of well-known phenomena such as the amyloid prions or fungal senescence. It will present in depth the "white/opaque" switch of Candida albicans and the "crippled growth" degeneration of the model fungus Podospora anserina. These are two of the most thoroughly studied epigenetic phenotypic switches. I will also discuss the "sectors" presented by many filamentous ascomycetes, for which a prion-based model exists but is not demonstrated. Finally, I will also describe intriguing examples of phenotypic instability for which an explanation has yet to be provided.
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Groebe K, Krause F, Kunstmann B, Unterluggauer H, Reifschneider NH, Scheckhuber CQ, Sastri C, Stegmann W, Wozny W, Schwall GP, Poznanović S, Dencher NA, Jansen-Dürr P, Osiewacz HD, Schrattenholz A. Differential proteomic profiling of mitochondria from Podospora anserina, rat and human reveals distinct patterns of age-related oxidative changes. Exp Gerontol 2007; 42:887-98. [PMID: 17689904 DOI: 10.1016/j.exger.2007.07.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Revised: 06/18/2007] [Accepted: 07/06/2007] [Indexed: 01/07/2023]
Abstract
According to the 'free radical theory of ageing', the generation and accumulation of reactive oxygen species are key events during ageing of biological systems. Mitochondria are a major source of ROS and prominent targets for ROS-induced damage. Whereas mitochondrial DNA and membranes were shown to be oxidatively modified with ageing, mitochondrial protein oxidation is not well understood. The purpose of this study was an unbiased investigation of age-related changes in mitochondrial proteins and the molecular pathways by which ROS-induced protein oxidation may disturb cellular homeostasis. In a differential comparison of mitochondrial proteins from young and senescent strains of the fungal ageing model Podospora anserina, from brains of young (5 months) vs. older rats (17 and 31 months), and human cells, with normal and chemically accelerated in vitro ageing, we found certain redundant posttranslationally modified isoforms of subunits of ATP synthase affected across all three species. These appear to represent general susceptible hot spot targets for oxidative chemical changes of proteins accumulating during ageing, and potentially initiating various age-related pathologies and processes. This type of modification is discussed using the example of SAM-dependent O-methyltransferase from P. anserina (PaMTH1), which surprisingly was found to be enriched in mitochondrial preparations of senescent cultures.
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van Doorn WG. Plant programmed cell death and the point of no return. TRENDS IN PLANT SCIENCE 2005; 10:478-83. [PMID: 16153879 DOI: 10.1016/j.tplants.2005.08.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2005] [Revised: 07/13/2005] [Accepted: 08/24/2005] [Indexed: 05/04/2023]
Abstract
The point of no return during programmed cell death (PCD) is defined as the step beyond which the cell is irreversibly committed to die. Some plant cells can be saved before this point by inducing the formation of functional chloroplasts. A visibly senescent tissue will then become green again and live for months or years. The mechanism of this reversal is only partially known. The point of no return in fungi and animals is often associated with lack of mitochondrial function. In plant cells that do not regreen, there is no evidence for PCD reversal that results in a long life. It is unclear why chloroplast-containing cells, in contrast to those with only mitochondria, have long lives after PCD reversal.
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Affiliation(s)
- Wouter G van Doorn
- Wageningen University and Research Center, PO Box 17, 6700 AA Wageningen, The Netherlands.
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Bertrand H. Role of Mitochondrial DNA in the Senescence and Hypovirulence of Fungi and Potential for Plant Disease Control. ANNUAL REVIEW OF PHYTOPATHOLOGY 2000; 38:397-422. [PMID: 11701848 DOI: 10.1146/annurev.phyto.38.1.397] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The unique coenocytic anatomy of the mycelia of the filamentous fungi and the formation of anastomoses between hyphae from different mycelia enable the intracellular accumulation and infectious transmission of plasmids and mutant mitochondrial DNAs (mtDNAs) that cause senescence. For reasons that are not fully apparent, mitochondria that are rendered dysfunctional by so-called "suppressive" mtDNA mutations proliferate rapidly in growing cells and gradually displace organelles that contain wild-type mtDNA molecules and are functional. The consequence of this process is senescence and death if the suppressive mtDNA contains a lethal mutation. Suppressive mtDNA mutations and mitochondrial plasmids can elicit cytoplasmically transmissible "mitochondrial hypovirulence" syndromes in at least some of the phytopathogenic fungi. In the chestnut-blight fungus Cryphonectria parasitica, the pattern of asexual transmission of mutant mtDNAs and mitochondrial plasmids resembles the pattern of "infectious" transmission displayed by the attenuating virus that is most commonly used for the biological control of this fungus. At least some of the attenuating mitochondrial hypovirulence factors are inherited maternally in crosses, whereas the viruses are not transmitted sexually. The natural control of blight in an isolated stand of chestnut trees has resulted from the invasion of the local population of C. parasitica by a senescence-inducing mutant mtDNA. Moreover, a mitochondrial plasmid, pCRY1, attenuates at least some virulent strains of C. parasitica, suggesting that such factors could be applied to control plant diseases caused by fungi.
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Affiliation(s)
- Helmut Bertrand
- Department of Microbiology, Michigan State University, East Lansing, Michigan 48824; e-mail:
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5
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Jamet-Vierny C, Rossignol M, Haedens V, Silar P. What triggers senescence in Podospora anserina? Fungal Genet Biol 1999; 27:26-35. [PMID: 10413612 DOI: 10.1006/fgbi.1999.1127] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Senescence of Podospora anserina is triggered by a cytoplasmic and infectious factor (the determinant of senescence) and is always correlated with mitochondrial DNA modifications, especially with the accumulation of small circular subgenomic DNA molecules, the senDNAs. Several observations have suggested that the senDNAs could be the cytoplasmic and infectious determinant. However, we show here (1) that senDNA molecules can be transferred to a young culture without the cotransmission of the determinant of senescence and (2) that the determinant of senescence does not segregate as a mitochondrial DNA mutation. Overall, our data strongly argue that amplification of senDNA molecules in the mitochondria is not an intrinsic property of these small DNA molecules. They question the nature of the actual determinant of senescence.
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Affiliation(s)
- C Jamet-Vierny
- Institut de Génétique et Microbiologie, URA 2225, Université de Paris Sud, Orsay cedex, 91405, France
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Hermanns J, Debets F, Hoekstra R, Osiewacz HD. A novel family of linear plasmids with homology to plasmid pAL2-1 of Podospora anserina. MOLECULAR & GENERAL GENETICS : MGG 1995; 246:638-47. [PMID: 7700237 DOI: 10.1007/bf00298971] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Three recently isolated wild-type strains of the ascomycete Podospora anserina were analyzed for the presence of linear mitochondrial plasmids. In one of these strains, designated Wat, at least 12 distinct plasmid-like elements were identified. From molecular analyses a minimum number of 78 individual linear molecules with proteins bound to their 5' ends was estimated. In addition, the different members of this family of typical linear plasmids were shown to possess a common central region and terminal sequences which differ from one plasmid to another due to the presence of different numbers of a 2.4 kb sequence module. Finally, the pWa6 plasmids share a high degree of sequence similarity with pAL2-1, a linear plasmid previously identified in mitochondria of a long-lived mutant of P.anserina. A mechanism is proposed which explains the generation of these distinct, closely related extra-chromosomal genetic traits.
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Affiliation(s)
- J Hermanns
- German Cancer Research Center, Department of Molecular Biology of Aging Processes, Heidelberg
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7
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Ebringer L. Interaction of drugs with extranuclear genetic elements and its consequences. TERATOGENESIS, CARCINOGENESIS, AND MUTAGENESIS 1990; 10:477-501. [PMID: 1982911 DOI: 10.1002/tcm.1770100606] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Bacterial ancestry of mitochondria and plastids is now generally accepted. Both organelles contain their own DNA and transcription-translation apparatus of a prokaryotic type. Due to this fact these systems carry bacteria-like properties. Thus organellar DNA and ribosomes are essentially different from nuclear DNA and cytoplasmic ribosomes in physical as well as in functional respects. Due to the bacterial character of both types of organelles they are susceptible to various antibacterial chemicals. Inhibitors of bacterial protein synthesis inhibit mitochondrial (plastidial) biogenesis. Therefore the cellular content of mitochondria (plastids)-made proteins decreases during cytoplasmic turnover or cell division in the presence of these drugs. Such drug activity consequently leads to a reduced capacity for oxidative phosphorylation or photosynthesis. Organellar genomes are less stable and more sensitive to mutagenesis as compared to nuclear genome. It means also that genotoxic agents induce various disorders of mitochondrial (plastidial) functions. Impairments in the respiratory chain are associated with structural as well as functional abnormalities of mitochondria. These are clinically expressed mostly in tissues with a high demand for ATP: brain, heart, skeletal muscle, and retina. On the other hand, some antibacterial inhibitors of mitochondrial biogenesis (e.g., tetracyclines) inhibit selectively tumor cell proliferation. Therefore they may be considered for use in anticancer therapy. The article summarizes the response of mitochondria and plastids in various organisms to drugs and environmental xenobiotics. Various model organisms suitable for detection of xenobiotic effect on mitochondria (plastids) are presented as well as the possible consequences of such interaction.
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Affiliation(s)
- L Ebringer
- Institute of Molecular and Subcellular Biology, Comenius University, Bratislava, Czechoslovakia
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9
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Vierny-Jamet C. Senescence in Podospora anserina: a possible role for nucleic acid interacting proteins suggested by the sequence analysis of a mitochondrial DNA region specifically amplified in senescent cultures. Gene 1988; 74:387-98. [PMID: 3246349 DOI: 10.1016/0378-1119(88)90172-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In Podospora anserina, the phenomenon of senescence was previously shown to be correlated with the presence of a senescence-specific DNA (sen-DNA) resulting from the amplification of some regions (alpha, beta, gamma, epsilon) of the mitochondrial chromosome. The beta region gives rise to sen-DNAs with variable sizes and junctions which share a 1,100-bp common sequence. Here we report the complete nucleotide sequence of one 4-kb beta sen-DNA. Included in the sequence are a large part of the first intron open reading frame (ORF) of the gene ND4L and three short unidentified ORFs more precisely located in the common beta region. The primary structure of the polypeptide possibly encoded by one of them is very similar to the glycine-rich domains present in various single-stranded DNA-binding proteins. The comparison of the information content of this beta sen-DNA with that of other previously sequenced sen-DNAs suggests that the role in the senescence process attributed to the sen-DNAs could be related to the overproduction of a variety of proteins which interact with nucleic acids.
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Affiliation(s)
- C Vierny-Jamet
- Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, Gif sur Yvette, France
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Wolf K, Del Giudice L. The variable mitochondrial genome of ascomycetes: organization, mutational alterations, and expression. ADVANCES IN GENETICS 1988; 25:185-308. [PMID: 3057820 DOI: 10.1016/s0065-2660(08)60460-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- K Wolf
- Institut für Genetik und Mikrobiologie, Universität München, Munich, Federal Republic of Germany
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Abstract
Two linear plasmid-like DNAs designated pFSC1 (9.2 kbp) and pFSC2 (8.3 kbp) were found in an isolate of the plant pathogenic fungus Fusarium solani f. sp. cucurbitae race 1. The plasmids were maternally inherited and copurified with mitochondrial DNA obtained from a mitochondria-enriched cell fraction suggesting that they are located in mitochondria. The plasmids did not share extensive sequence similarity. No homology was detected between either plasmid and the nuclear or mitochondrial genome when cloned plasmids were used as probes in Southern hybridization analyses. The fungus was cured of plasmids by ethidium bromide treatment. Compared to the plasmid-containing isolate, plasmid-cured derivatives had reduced pathogenicity on a susceptible plant host, Cucurbita maxima "Pink Banana."
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Affiliation(s)
- D A Samac
- Department of Plant Pathology, University of Wisconsin, Madison
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Turker MS, Cummings DJ. Podospora anserina does not senesce when serially passaged in liquid culture. J Bacteriol 1987; 169:454-60. [PMID: 3804968 PMCID: PMC211798 DOI: 10.1128/jb.169.2.454-460.1987] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
A procedure was developed for the prolonged growth of the ascomycete fungus Podospora anserina in liquid culture to determine the effects of such growth on the senescence phenotype. Senescence in P. anserina, which is maternally inherited and associated with the excision and amplification of specific mitochondrial plasmids, occurs when this species is grown on solid medium. In two independent experiments no evidence of senescence was observed as mycelia were serially passaged in liquid culture. Further, when separable mycelial masses, termed puff balls, from the liquid cultures were plated on solid medium, a significant increase in their average longevity was observed. The apparent immortality of P. anserina in liquid culture was not dependent upon mitochondrial DNA rearrangements, nor was it affected by the presence of a previously described senescence plasmid, alpha senDNA. Evidence was obtained indicating that growth in liquid culture exerts selective pressure to maintain the wild-type mitochondrial genome.
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Does nuclear integration of mitochondrial sequences occur during senescence in Podospora? Nature 1986. [DOI: 10.1038/324597a0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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14
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The in vivo effect of acriflavine on mitochondrial functions in the petite negative yeast Hansenula saturnus. Curr Genet 1986. [DOI: 10.1007/bf00378204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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15
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Sainsard-Chanet A, Begel O. Transformation of yeast and Podospora: innocuity of senescence-specific DNAs. ACTA ACUST UNITED AC 1986. [DOI: 10.1007/bf00331022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Despite mtDNA polymorphism the mobile intron (plDNA) of the COI gene is present in ten different races of Podospora anserina. Curr Genet 1985. [DOI: 10.1007/bf00418494] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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17
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Koll F, Belcour L, Vierny C. A 1100-bp sequence of mitochondrial DNA is involved in senescence process in Podospora: study of senescent and mutant cultures. Plasmid 1985; 14:106-17. [PMID: 2999848 DOI: 10.1016/0147-619x(85)90070-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In Podospora, senescence is assumed to be caused by the amplification of short sequences of the mitochondrial genome (sen-DNAs). We have characterized a 1100-bp-long mitochondrial DNA sequence which could be directly involved in the phenomenon. Indeed, by hybridization experiments, we show that this sequence is both present in all the sen-DNA molecules which originate from the beta region of the mitochondrial chromosome and rearranged in the mitochondrial genome of two mitochondrial mutants selected as resistant to senescence.
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Bertrand H, Chan BS, Griffiths AJ. Insertion of a foreign nucleotide sequence into mitochondrial DNA causes senescence in Neurospora intermedia. Cell 1985; 41:877-84. [PMID: 2408762 DOI: 10.1016/s0092-8674(85)80068-4] [Citation(s) in RCA: 124] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The kalilo variants of Neurospora contain a cytoplasmic genetic factor that causes senescence. This factor is a 9.0 kb transposable element (kalDNA) that lacks nucleotide sequence homology with mtDNA and is inserted into the mitochondrial chromosome, often at sites located within the open reading frame in the intron-DNA of the mitochondrial 25S-rRNA gene. Genomes containing the "foreign" DNA insert accumulate during growth, and death occurs as the cells become deficient in functional large and small subunits of mitochondrial ribosomes. The kalDNA transposon may be an "activator" element that causes breaks in mtDNA. Nonsenescing [+] strains of Neurospora do not contain kalDNA.
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Abstract
In the fungus Podospora, a correlation has recently been established between the presence of circular DNA molecules arising from the mitochondrial genome (SEN-DNAs) and the senescence syndrome. Here, I propose a hypothesis which accounts for the initial event which leads to the first SEN-DNA. A molecule in the most frequent situation where the SEN-DNA is an intron which might code for a maturase. This hypothesis is based upon several observations made either in Podospora or in the yeast S. cerevisiae. It assumes that mitochondrially synthesized maturases are unspecific nucleases able to work at the level of RNA and DNA molecules. Their specificity for RNA splicing instead of DNA is given by cytoplasmic proteins. Therefore, if the balance between cytoplasmic and mitochondrial protein syntheses is disturbed in favour of the mitochondrial compartment, the maturase would be accumulated and allowed to splice introns from DNA instead of RNA molecules. This hypothesis can account for aging of higher eucaryotic cells by postulating analogous processes in their nuclear compartment.
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Kück U, Osiewacz HD, Schmidt U, Kappelhoff B, Schulte E, Stahl U, Esser K. The onset of senescence is affected by DNA rearrangements of a discontinuous mitochondrial gene in Podospora anserina. Curr Genet 1985; 9:373-82. [PMID: 2836091 DOI: 10.1007/bf00421608] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Mapping and transcription studies have revealed that in Podospora anserina the causative agent of senescence, a mitochondrial plasmid (plDNA), is identical with intron 1 of the discontinuous gene for cytochrome-c-oxidase subunit 1 (COI), which is 2 kpb from the discontinuous gene for cytochrome b (Cytb). A mitochondrial mutant (ex1) devoid of the COI, but not of the Cytb gene provides longevity. A molecular model for the onset of senescence is presented.
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Affiliation(s)
- U Kück
- Lehrstuhl für Allgemeine Botanik, Ruhr-Universität Bochum, Federal Republic of Germany
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Bégueret J, Razanamparany V, Perrot M, Barreau C. Cloning gene ura5 for the orotidylic acid pyrophosphorylase of the filamentous fungus Podospora anserina: transformation of protoplasts. Gene X 1984; 32:487-92. [PMID: 6530144 DOI: 10.1016/0378-1119(84)90023-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
From a genomic library of the filamentous fungus Podospora anserina, we have cloned a 4.9-kb fragment which complements an Escherichia coli mutant strain deficient for orotidylic acid pyrophosphorylase (pyrE gene). The recombinant plasmid pPAura5 also transforms to prototrophy a mutant strain of P. anserina carrying a mutation in the ura5 gene and lacking OMPppase activity.
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Jamet-Vierny C, Begel O, Belcour L. A 20 X 10(3)-base mosaic gene identified on the mitochondrial chromosome of Podospora anserina. EUROPEAN JOURNAL OF BIOCHEMISTRY 1984; 143:389-94. [PMID: 6468401 DOI: 10.1111/j.1432-1033.1984.tb08385.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
By DNA sequencing and hybridization experiments we have localized the genes cob and col on the mitochondrial chromosome of Podospora anserina. The positions we have determined for these two genes are different from those previously attributed to them. The presence in the gene col of at least two introns, belonging respectively to class I and II, has been demonstrated. This gene, with a size of about 20 X 10(3) bases, appears to be the longest known mitochondrial mosaic gene.
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