Recurrent Senescence in Axenic Cultures of Physarum polycephalum

Hu, Fu-Sen; Clark, Jim; Lott, Timothy J.

doi:10.1099/00221287-131-4-811

Cited by 5 publications

(7 citation statements)

References 10 publications

(11 reference statements)

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“…Nonetheless our evidence demonstrated that the long-lived puff ball-derived cultures were recessive to a wild-type strain when crossed as a male parent and in confrontational crosses. Young plasmodia (i.e., long lived) of a second slime mold with a senescent program, Didymium iridus, were usually recessive to old plasmodia (i.e., short lived) in heterokaryons (3), as was an immortal mutant of P. polycephalum (10). In marked contrast to this latter finding, the L14a2 mutant was dominant when crossed as a male, indicating a nuclear component to its phenotype, and in confrontational crosses.…”

Section: >125 (3)contrasting

confidence: 41%

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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)contrasting

confidence: 41%

“…Physarum polycephalum organisms were maintained for very long times in liquid culture (>700 days) a significant decrease in longevity was observed (10).…”

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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“…They are currently more than 2 years old and none of them has died so far. In previous reports, plasmodium lifespan has been shown to vary from one month to 1 year, depending on the strain [61][62][63]. Hence, we considered as 'old', slime moulds that were over 1 year old and 'very-old' slime moulds were those that were almost 2 years old.…”

Section: Methods (A) Species Studied and Rearing Conditionsmentioning

confidence: 99%

“…The lifespan of the plasmodium is in part genetically determined as different strains have different lifespans, and subclones derived from a single plasmodium age in a coordinated manner, i.e. death occurs at approximately the same time [61,63,64].…”

Section: Introductionmentioning

confidence: 99%

“…A plasmodium can be maintained for months, during which no change is apparent until a reproducible decline in viability occurs [61]. Senescence in the plasmodial stage is characterized by morphological change [61], reduction of growth rate [61,67], reduced cytoplasmic flow [63], loss of yellow pigment [63], accumulation of polyploid nuclei [68], high level of mitochondrial DNA fragmentation [67], decreased replication of mitochondrial DNA [62], and increase in nuclear size and DNA content [68,69]. Senescence ends with the fragmentation of the plasmodium into several small spherical structures, with a concomitant lysis of the plasmodium [63].…”

Section: Introductionmentioning

confidence: 99%

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Behavioural changes in slime moulds over time

Rolland

Pasquier

Paul

et al. 2023

Phil. Trans. R. Soc. B

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Changes in behaviour over the lifetime of single-cell organisms have primarily been investigated in response to environmental stressors. However, growing evidence suggests that unicellular organisms undergo behavioural changes throughout their lifetime independently of the external environment. Here we studied how behavioural performances across different tasks vary with age in the acellular slime mould Physarum polycephalum . We tested slime moulds aged from 1 week to 100 weeks. First, we showed that migration speed decreases with age in favourable and adverse environments. Second, we showed that decision making and learning abilities do not deteriorate with age. Third, we revealed that old slime moulds can recover temporarily their behavioural performances if they go throughout a dormant stage or if they fuse with a young congener. Last, we observed the response of slime mould facing a choice between cues released by clone mates of different age. We found that both old and young slime moulds are attracted preferentially toward cues left by young slime moulds. Although many studies have studied behaviour in unicellular organisms, few have taken the step of looking for changes in behaviour over the lifetime of individuals. This study extends our knowledge of the behavioural plasticity of single-celled organisms and establishes slime moulds as a promising model to investigate the effect of ageing on behaviour at the cellular level. This article is part of a discussion meeting issue ‘Collective behaviour through time’.

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In vitro DNA fragmentation of mitochondrial DNA caused by single-stranded breakage related to macroplasmodial senescence of the true slime mold, Physarum polycephalum

Abe¹,

Takano²,

Sasaki³

et al. 2000

Current Genetics

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We found that mitochondrial DNA (mtDNA) isolated from Physarum polycephalum fragmented itself in weak ionic solutions. The mtDNA was dissolved in STE (saline Tris-EDTA: 150 mM NaCl, 10 mM Tris-HCl, 1 mM EDTA), TE (10 mM Tris-HCl, 1 mM EDTA) and DW, and then electrophoresed in an agarose gel. The intact 86-kbp mtDNA band was seen in STE, but several novel bands appeared in TE and DW. In TE, two discrete bands appeared at 6.7-kbp (alpha-band) and 5.0-kbp (beta-band), whereas at least 17 discrete bands were observed in distilled water (DW). These fragmentation patterns were not stoichiometric, as seen when using restriction endonucleases, but were clearly different from the degradation of DNA caused by a physical shearing force or a contaminating nuclease. In this paper, we characterize this in vitro fragmentation of mtDNA from P. polycephalum. We located 19 fragments, including the alpha and beta fragments, on a mtDNA restriction map, and demonstrated that these cleavage sites were S1 nuclease-sensitive regions, which are single-stranded DNA regions such as nicks and gaps in the mtDNA. The alpha and beta fragments are derived from the region encoding ribosomal RNAs (rRNAs) and the ATP synthase (atpA) gene, while the other 17 fragments are not derived from any specific region, but the cleavage sites are located throughout the mtDNA molecule. In P. polycephalum, it is well known that the growth rate of macroplasmodia decreases with aging. Equal amounts of mtDNA from juvenile and aged macroplasmodia were electrophoresed and the frequency of the beta fragment in each sample was measured. The ratio of the beta band to the total signal including background was estimated to be 3.3-4.0% in juvenile macroplasmodia, whereas it increased to 8.3-28.2% in aged macroplasmodia. This result suggests that the in vitro fragmentation of mtDNA is associated with macroplasmodial senescence. The single-stranded breakage of mtDNA of P. polycephalum may accumulate with age.

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Recurrent Senescence in Axenic Cultures of Physarum polycephalum

Cited by 5 publications

References 10 publications

Podospora anserina does not senesce when serially passaged in liquid culture

Podospora anserina does not senesce when serially passaged in liquid culture

Behavioural changes in slime moulds over time

In vitro DNA fragmentation of mitochondrial DNA caused by single-stranded breakage related to macroplasmodial senescence of the true slime mold, Physarum polycephalum

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