Ethidium bromide rejuvenation of senescent cultures of Podospora anserina : Loss of senescence-specific DNA and recovery of normal mitochondrial DNA

Begel, Odile; Keller, Anne‐Marie; Vierny, Corinne; Belcour, Léon

doi:10.1007/bf00420231

Cited by 42 publications

(8 citation statements)

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“…Although we also found an increase in longevity with ethidium bromide, we found no effect with streptomycin (unpublished). It has been shown that ethidium bromide can rejuvenate senescent cultures of P. anserina, presumably by allowing for the preferential replication of the wild-type mitochondrial genome (13). In this respect rejuvenation with ethidium bromide is similar to our observations that the liquid cultures displayed only the wild-type mitochondrial genome and that growth in liquid culture will preferentially select for a wild-type mitochondrial genome over a mutant one.…”

Section: >125 (3)supporting

confidence: 86%

“…3 A significant difference remains, however, between the observations of "rejuvenation" with ethidium bromide and immortality in liquid culture. When cultures grown on ethidium bromide, which are immortal in the presence of this drug (25), are removed from its presence the cultures resume a wild-type longevity pattern (13). When we removed P. anserina organisms from liquid culture and allowed the puff balls to resume growth on solid medium, their average longevity was significantly increased.…”

Section: >125 (3)mentioning

confidence: 99%

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Podospora anserina does not senesce when serially passaged in liquid culture

Turker

Cummings

1987

J Bacteriol

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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 The ascomycete fungus Podospora anserina provides a model system for the study of senescence at the molecular level. When mycelial plugs are placed on corn meal agar in race tubes, growth occurs at a constant rate for a genetically determined distance (19,20). The sudden cessation in vegetative growth which follows is termed senescence. Age is therefore measured as a function of the distance grown in centimeters. There are at least 10 different races of P. anserina, each with a characteristic longevity when grown in race tubes (14).Early investigations of senescence in P. anserina demonstrated that senescence is maternally inherited (19, 20). Ensuing studies have demonstrated that senescence is associated with the excision and amplification of specific mitochondrial DNA sequences and mitochondrial DNA rearrangements (5, 22). The resultant plasmids, termed senDNAs, were found in cultures derived from senescent mycelium. At least six different senDNAs have been reported (1, 5-7, 11, 22, 28), but one particular 2.6-kilobasepair plasmid, asenDNA, is the most common senDNA found in senescent cultures. The other senDNAs occur relatively infrequently, and some have only been reported once. Unlike the other senDNA plasmids, the asenDNA plasmid is also found in young, nonsenescent mycelia of race A, although in lesser amounts (26). This plasmid consists of a complete group II intron of the highly mosaic COI gene, and it possesses an open reading frame with extensive homology to retroviral reverse transcriptase (18). A second class of mitochondrial plasmids, termed sMt-DNAs, have recently been described in P. anserina (M. S. Turker, J. M. Domenico, and D. J.Cummings, J. Biol. Chem., in press).These plasmids are associated with longevity mutants, which are defined as strains capable of growth renewal after one or more senescent crises on solid medium. Similar to senescent cultures, such mutants usually yield mitochondrial DNAs with extensive rearrangements (2, 15; D. J. Cummings, M. S. Turker, and J. M. Domenico, in press). Figure 1 shows the most current restriction map for P. anserina mitochondrial DNA and the locations from which several of the excision amplification plasmids are derived.For this study we investigated the kinetics of P. anserina senescence in liquid culture by developing a procedure for the serial passage of homogenized mycelia. The most striking observation was that P. anserina did not senesce when grown continuously in liquid culture. Fqrther, when small masses of the liquid culture-grown mycelia, termed puff balls, were returned to growth on ...

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Section: >125 (3)supporting

confidence: 86%

Section: >125 (3)mentioning

confidence: 99%

Podospora anserina does not senesce when serially passaged in liquid culture

Turker

Cummings

1987

J Bacteriol

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“…This is based on several observations. First, the behavior of the senDNAs is consistent with that of the determinant of senescence since their amount increases during the senescence process and they disappear during rejuvenation of the strains (Koll et al, 1984). Second, deletion of the mtDNA regions generating senDNAs results in immortality of the strains (Belcour and Vierny, 1986;Koll et al, 1985).…”

Section: Academic Presssupporting

confidence: 55%

What Triggers Senescence in Podospora anserina?

Jamet‐Vierny

Rossignol

Haedens

et al. 1999

Fungal Genetics and Biology

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“…In this species, senescence is clearly associated with mtDNA rearrangements and most probably is caused by them. More precisely, it has been shown that short mtDNA sequences are amplified as circular multimeric DNA molecules in senescent cultures (9)(10)(11)(12)(13)(14). It was shown that the most frequently amplified sequence corresponds exactly to a mitochondrial intron (15), intron a, and that most of the mutations allowing mycelia to escape senescence are rearrangements in intron a (12,(16)(17)(18).…”

Section: Introductionmentioning

confidence: 99%

A site-specific deletion in mitochondrial DNA of Podospora is under the control of nuclear genes.

Belcour

Begel

Picard

1991

Proc. Natl. Acad. Sci. U.S.A.

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In the filamentous fungus Podospora anserina, the association of two nuclear genes inevitably leads to a "premature death" phenotype consisting of an early end of vegetative growth a few days after ascospore germination. Mycelia showing this phenotype contain a mitochondrial chromosome that always bears the same deletion. One of the break points is exactly at the 5' splice site of a particular mitochondrial intron, suggesting that the deletion event could result from molecular mechanisms also involved in intron mobility.One of the nuclear genes involved in triggering this site-specific event belongs to the mating-type minus haplotype; the other is a mutant allele of a gene encoding a cytosolic ribosomal protein.In obligate aerobes, rearrangements of mitochondrial DNA (mtDNA) are responsible for various deleterious symptoms, such as maternally inherited male sterility in plants (1), several mycelial degenerative phenomena in fungi (2), and, as described more recently in humans, numerous neuromuscular (3) or hematological (4) diseases. In some cases, nuclear genes have been shown to control the mtDNA rearrangements (5, 6). The molecular mechanisms producing these rearrangements and the role played by nuclear-encoded proteins remain unclear in all cases.In the filamentous fungus Podospora anserina, vegetative growth is limited by a maternally inherited syndrome, called senescence, ending in cessation of mycelial elongation and apical cell death (7,8). In this species, senescence is clearly associated with mtDNA rearrangements and most probably is caused by them. More precisely, it has been shown that short mtDNA sequences are amplified as circular multimeric DNA molecules in senescent cultures (9)(10)(11)(12)(13)(14). It was shown that the most frequently amplified sequence corresponds exactly to a mitochondrial intron (15), intron a, and that most of the mutations allowing mycelia to escape senescence are rearrangements in intron a (12,(16)(17)(18). It has been known for a long time (19) that the nuclear genome controls the life-span of the fungus. For instance, the life-span of our reference strains differs according to their mating type: the process of senescence is delayed in mat+ strains compared with matones. However the differences, although significant, are not striking (see Table 1). Moreover the functions encoded by these genes are still unknown.The work presented here follows the observation that, in Podospora, mutations in several genes involved in the control of translational accuracy have an effect on the life-span (A. Raynal, personal communication; Table 1). As a first step, we focused our attention on the AS1-4 mutation. This particular allele confers a very long life-span to mat+ mycelia, while, when associated with mat-, it leads systematically to the premature death phenotype, consisting of an early end of mycelial growth a few days after ascospore germination.We showed that mycelia presenting this phenotype were in all cases heteroplasmic and that they systematically contained the same ...

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Ethidium bromide rejuvenation of senescent cultures of Podospora anserina : Loss of senescence-specific DNA and recovery of normal mitochondrial DNA

Cited by 42 publications

References 22 publications

Podospora anserina does not senesce when serially passaged in liquid culture

Podospora anserina does not senesce when serially passaged in liquid culture

What Triggers Senescence in Podospora anserina?

A site-specific deletion in mitochondrial DNA of Podospora is under the control of nuclear genes.

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