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  • 1
    Electronic Resource
    Electronic Resource
    A new senescence-inducing mitochondrial linear plasmid in field-isolated Neurospora crassa strains from India (1991)
    Springer
    Current genetics 19 (1991), S. 129-137 
    Details
    ISSN: 1432-0983
    Keywords: Senescence ; Plasmid ; Neurospora ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Several field-collected strains of Neurospora crassa from the vicinity or Aarey, Bombay, India, are prone to precocious senescence and death. Analysis of one strain, Aarely-1e, demonstrated that the genetic determinants for the predisposition to senescence are maternally inherited. The senescence-prone strains contain a 7-kb, linear, mitochondrial DNA plasmid, maranhar, which is not present in long-lived isolates from the same geographical location. The maranhar plasmid has inverted terminal repeats with protein covalently bound at the 5′ termini. Molecular hybridization experiments have demonstrated no substantial DNA sequence homology between the plasmid and the normal mitochondrial (mtDNA) and nuclear genomes of long-lived strains of N. crassa. Integrated maranhar sequences were detected in the mtDNAs of two cultures derived from Aarey-1e, and mtDNAs with the insertion sequences accumulated during subculturing. Nucleotide sequence analysis of cloned fragments of the two insertion sequences demonstrates that that they are flanked by long inverted repeats of mtDNA. The senescence syndrome of the maranhar strains, and the mode of integration of the plasmid, are reminiscent of those seen in the kalilo strains of N. intermedia. Nonetheless, there is no detectable nucleotide sequence homology between the maranhar and kalilo plasmids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326294
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  • 2
    Electronic Resource
    Electronic Resource
    Inversions and recombinations in mitochondrial DNA of the (SG-1) cytoplasmic mutant in two Neurospora species (1986)
    Springer
    Current genetics 10 (1986), S. 607-617 
    Details
    ISSN: 1432-0983
    Keywords: Neurospora ; mtDNA ; Inversions ; Recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mitochondrial DNAs of [SG-1] cytoplasmically-mutant and wild-type strains of Neurospora crassa and Neurospora sitophila were examined by comparative restriction endonuclease analyses. The mtDNA of N. sitophila wild type of Whitehouse differs from type II mtDNA of N. crassa by insertions of 3.3 kb in EcoRI-9, and 1.2 kb in EcoRI-3, and a deletion of 1.1 kb in EcoRI-5. These DNA heteromorphisms provided convenient markers for tracing N. crassa [SG-1] mtDNA during and after its transfer into N. sitophila. The [SG-1] cytoplasmic mutant in both N. crassa and N. sitophila has a distinctive inversion that connects the fragment EcoRI-4 with HindIII-10a. The [SG-1] mtDNA from N. crassa remained essentially intact after it was transferred by crosses into N. sitophila. In each species, a unique second inversion occured in the [SG-1] mtDNA after the transfer was made. In N. sitophila, polar recombination in heteroplasmons between [SG-1] and wild-type preferentially yields strains with mtDNAs that contain the maximum possible number of insertions in the cob and co-1 loci of the EcoRI-3 region of the mitochondrial chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418128
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  • 3
    Electronic Resource
    Electronic Resource
    The kalilo senescence plasmid of Neurospora intermedia has covalently-linked 5′ terminal proteins (1990)
    Springer
    Current genetics 17 (1990), S. 195-201 
    Details
    ISSN: 1432-0983
    Keywords: Neurospora ; Plasmid ; Terminal proteins ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Kalilo is a linear plasmid associated with senescence in Neurospora. The terminal Eco R1 restriction fragments of this element are linked to a protein component which remains bound despite denaturation with high concentrations of SDS. Following digestion with proteinase K, the 5′ termini of the plasmid remain resistant to lambda exonuclease whereas the 3′ termini are sensitive to exonuclease III, suggesting that the terminal protein is covalently linked. From an analysis of iodinated proteins released by nuclease digestion, the size of the terminal protein was estimated to be 120 kDa. The covalent linkage between DNA and protein was shown to be alkali-labile suggesting that it is a phosphodiester bond. Electron micrographs of the intact plasmid demonstrate that the associated proteins are terminal, and may be involved in replication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312610
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  • 4
    Electronic Resource
    Electronic Resource
    Unstable cytoplasms in Hawaiian strains of Neurospora intermedia (1984)
    Springer
    Current genetics 8 (1984), S. 387-398 
    Details
    ISSN: 1432-0983
    Keywords: Cytoplasm ; Mitochondria ; Neurospora ; Senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary By subjecting a large sample of natural isolates of N. intermedia to prolonged serial subculturing, 26 cytoplasmic variants have been identified. These variants show senescence, and finally death at some strain-specific point in the subculture series. All senescent strains are from the Hawaiian archipelago, where their incidence in natural populations is high. Senescent cultures can be female-fertile. Random ascospore analyses show that (i) senescence is maternally inherited; (ii) different stages of senescence give different proportions of senescent progeny; and (iii) ascospores from one cross show different degrees of senescence. These results indicate that senescence is determined by a genetic factor which re sides in the cytoplasm. This factor promotes instability of the cytoplasm, resulting initially in cytoplasmic heterogeneity shown by ascus and conidium sampling, and finally in death. Molecular studies to be published elsewhere show that the progression through senescence to death is correlated with the occurence of abnormalities in cytochrome content and mitochondrial DNA. The Hawaiian word kalilo (dying), symbolised [kal], is proposed to denote these cytoplasms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00419828
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  • 5
    Electronic Resource
    Electronic Resource
    The kalilo linear senescence-inducing plasmid of Neurospora is an invertron and encodes DNA and RNA polymerases (1991)
    Springer
    Current genetics 20 (1991), S. 225-237 
    Details
    ISSN: 1432-0983
    Keywords: Neurospora ; Senescence ; kalilo plasmid ; Mitochondria ; DNA sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nucleotide sequence of kalilo, a linear plasmid that induces senescence in Neurospora by intergrating into the mitochondrial chromosome, reveals structural and genetic features germane to the unique properties of this element. Prominent features include: (1) very long perfect terminal inverted repeats of nucleotide sequences which are devoid of obvious genetic functions, but are unusually GC-rich near both ends of the linear DNA; (2) small imperfect palindromes that are situated at the termini of the plasmid and are cognate with the active sites for plasmid integration into mtDNA; (3) two large, non-overlapping open-reading frames, ORF-1 and ORF-2, which are located on opposite strands of the plasmid and potentially encode RNA and DNA polymerases, respectively, and (4) a set of imperfect palindromes that coincide with similar structures that have been detected at more or less identical locations in the nucleotide sequences of other linear mitochondrial plasmids. The nucleotide sequence does not reveal a distinct gene that codes for the protein that is attached to the ends of the plasmid. However, a 335-amino acid, cryptic, N-terminal domain of the putative DNA polymersse might function as the terminal protein. Although the plasmid has been co-purifed with nuclei and mitochondria, its nucleotide composition and codon usage indicate that it is a mitochondrial genetic element.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326237
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  • 6
    Electronic Resource
    Electronic Resource
    Heterokaryotic transmission of senescence plasmid DNA in Neurospora (1990)
    Springer
    Current genetics 17 (1990), S. 139-145 
    Details
    ISSN: 1432-0983
    Keywords: Neurospora ; Senescence ; Plasmids ; Mitochondrial DNA ; Heterokaryons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Heterokaryotic transmission is one of the major techniques for the study of cytoplasmic inheritance and here we have applied it to the senescence-determining plasmids kalilo (Hawaiian) and maranhar (Indian). We have shown that kalilo-based senescence is effectively transmitted by cytoplasmic contact, both in N. crassa and in N. intermedia. In the first place, the heterokaryons themselves are senescent, confirming the suppressivity of the senescence phenotype in mixtures of normal and senescent cytoplasms. Second, senescence is found in new nuclear associations, as shown by analysis of conidial isolates and meiocytes stemming from the heterokaryons. In addition, the free plasmid AR-kalDNA, and its form that is inserted into mtDNA, (mtIS-kalDNA), are both transmitted to new nuclear associations. In a transient fusion between senescent N. intermedia and nonsenescent N. crassa cells, AR-kalDNA was transmitted to N. crassa and mtIS-kalDNA was transmitted to N. crassa mtDNA. A cryptic mitochondrial plasmid, not associated with senescence, was also transmitted very efficiently to N. crassa mitochondria. In mixed kalilo/maranhar fusions, both plasmids coexisted, approximately equally, in the heterokaryons themselves, and in conidial isolates. However, in sexual derivatives, AR-marDNA was in an excess and AR-kalDNA was sometimes absent. The efficient heterokaryotic transmission of these elements suggests that this is one of their natural modes of spread in populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00312859
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  • 7
    Electronic Resource
    Electronic Resource
    Genetic organization and structural features of maranhar, a senescence-inducing linear mitochondrial plasmid of Neurospora crassa (1992)
    Springer
    Current genetics 22 (1992), S. 385-397 
    Details
    ISSN: 1432-0983
    Keywords: Neurospora ; Mitochondria ; Linear plasmid ; Senescence ; Invertron
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nucleotide sequence of maranhar, a senescence-inducing linear mitochondrial plasmid of Neurospora crassa, was determined. The termini of the 7-kb plasmid are 349-bp inverted repeats (TIRs). Each DNA strand contains a long open reading frame (ORF) which begins within the TIR and extends toward the centre of the plasmid. ORF-1 codes for a single-subunit RNA polymerase that is not closely related to that encoded by another Neurospora plasmid, kalilo. The ORF-2 product may be a B-type DNA polymerase resembling those encoded by terminal protein-linked linear genetic elements, including linear mitochondrial plasmids and linear bacteriophages. A separate coding sequence for the terminal protein could not be identified; however, the DNA polymerase of maranhar has an amino-terminal extension with features that are also present in the terminal proteins of linear bacteriophages. The N-terminal extensions of the DNA polymerases of other linear mitochondrial plasmids contain similar features, suggesting that the terminal proteins of linear plasmids may be comprised, at least in part, of these cryptic domains. The terminal protein-DNA bond of maranhar is resistant to mild alkaline hydrolysis, indicating that it might involve a tyrosine or a lysine residue. Although maranhar and the senescence-inducing kalilo plasmid of N. intermedia are structurally similar, and integrate into mitochondrial DNA by a mechanism thus far unique to these two plasmids, they are not closely related to each other and they do not have any nucleotide sequence features, or ORFs, that distinguish them clearly from mitochondrial plasmids which are not associated with senescence and most of which are apparently non-integrative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00352440
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  • 8
    Electronic Resource
    Electronic Resource
    Linear kalilo DNA is a Neurospora mitochondrial plasmid that integrates into the mitochondrial DNA (1989)
    Springer
    Molecular genetics and genomics 220 (1989), S. 113-120 
    Details
    ISSN: 1617-4623
    Keywords: Neurospora ; Senescence ; Mitochondria ; Plasmid ; Kalilo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The linear autonomous form of kalilo DNA (previously called AR-kalDNA) is shown to be resident within mitochondria rather than nuclei, as had been suggested by previous experiments. This form has been renamed mtAR-kalDNA, to signify its mitochondrial location. Experiments are described that illustrate the inheritance and somatic transmission patterns of the mitochondrial kalilo plasmid and the mitochondrial inserted form of kalilo DNA (mtlS-kalDNA). Progeny of a cross with a pre-senescent subculture as the female parent inherited mtAR-ka1DNA only; mtIS-kalDNA was not transmitted sexually. During somatic propagation of the ascospore cultures, novel kalilo DNA inserts appeared and most of them persisted until death. We propose that these inserts originated from de novo integration of mtAR-kalDNA into the mitochondrial DNA. In two of the ascopore-derived series analyzed, the first inserts detected were seen only transiently and inserts appearing subsequent to the transient inserts were retained until death. We propose that these enduring inserts originated either from rearrangements of the transient inserts or from novel integration events, either from mtAR-kalDNA or from transposition of the transient inserts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260864
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