Nuclear DNA Content and Senescence in Physarum polycephalum

McCULLOUGH, Clare H. R.; Cooke, D.; Foxon, Jennifer L.; Sudbery, Peter E.; Grant, William D.

doi:10.1038/newbio245263a0

Cited by 25 publications

(6 citation statements)

References 9 publications

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“…The factors determining longevity are associated with genotype, and both short-and long-lived individuals can be created by the mating of appropriate haploid gametes (Lott & . Plasmodial ageing (senescence) has also been observed in isolates of the closely related species Physarum polycephalum (McCullough et al, 1973;Poulter, 1969;Daniel & Baldwin, 1964).…”

Section: Introductionmentioning

confidence: 98%

Sclerotization in Relation to Plasmodial Senescence in the Acellular Slime Mould Didymium iridis

Lott

Clark

1982

Microbiology

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When subjected to dehydration, Didymium iridis plasmodia differentiate into sclerotia which can be maintained for long periods and exhibit no discernible 0, uptake. While actively growing plasmodia display the phenomenon of senescence, this ageing is delayed in sclerotia by the duration of the sclerotized state. Upon rehydration, plasmodia live the remainder of their characteristic life spans. Hence, the timing mechanism for senescence is conserved during this reversible differentiation pathway. M E T H O D S The numeric nomenclature for both haploid myxamoebae and diploid plasmodia follows that of Collins (196 1 j. The initial formations of short-and long-lived plasmodia (genotypes 10.76 and 2.7, respectively) were performed in 60 x 20 mm Petri dishes containing half-strength corn meal agar as previously described (Collins, 1961).

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Section: Introductionmentioning

confidence: 98%

Sclerotization in Relation to Plasmodial Senescence in the Acellular Slime Mould Didymium iridis

Lott

Clark

1982

Microbiology

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“…There are numerous indications in the Physarum literature that variations of chromosome number and DNA-content characterize this organism (12)(13)(14). However, the confidence limits of these previous evaluations are comparatively large and, in our opinion, preclude definitive interpretations (cf., for example, chromosome counts, Figs.…”

Section: Discussionmentioning

confidence: 93%

Flow cytometry reveals a high degree of genomic size variation and mixoploidy in various strains of the acellular slime mold Physarum polycephalum

et al. 1986

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High-resolution flow cytometry, using avian erythrocytes as an internal standard, was employed to study constitutive genome size variation of GX-phase nuclei of Physarurn polgcephalum strains during the macroplasmodial stage of their life cycle. Our results document a previously unknown extent of genome size variation and mixoploidy in this organism. The unimodal diploid strain Tu 291 displayed the largest genome of the strains tested; in contrast, the Colonia strain displayed only half of the Tu 291 G2-phase fluorescence, confirming its haploid nature. An additional strain, derived from a recent cross between Lu897 and Lu898 amoebae, must have arisen by selfing (propagation of only one of the parental genomes to the macroplasmodial stage), since its nuclei display close to the haploid GX-phase DNA content. The observation of a small fraction of corresponding diploid nuclei within the haploid population of this strain, while maintained as microplasmodia, supports the notion that meiosis in haploid strains may require the presence of diploid nuclei. Two of the descendants of the prototype haploid Colonia strain, which were kept for extended periods of time in submerse culture, proved to be near diploid and mixoploid. Polyploidization and subsequent loss of DNA thus seems to contribute to the extremes of genome size variation in Physarum. In addition to unimodal fluorescence distributions, a number of diploid strains displayed bi-and even trimodal distributions within harvests of a single G2-phase macroplasmodium. Analysis of these mixoploid strains by means of gaussian curve-fitting suggests that the smaller genome size differences in Phgsarum may arise in step-wise diminution of DNA in approximate units of 3 4 % of the original Tu 291 genome.

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“…It should be pointed out that one can readily distinguish these nuclei at the microscopic level merely by visual inspection of stained material. Variable DNA contents within a single plasmodium of a closely related species, Physarum polycephalum, have been reported (Mohberg et aI., 1973;Laffler and Dove, 1977) and both autopolyploidy and plasmodial senescence (McCullough et al, 1973) have been advanced as possible explanations for this commonly observed situation. Inasmuch as we used only young plasmodia we can rule out senescence as a possible explanation.…”

Section: Results-as Already Described Under Ge-netic Experiments a Tmentioning

confidence: 99%

Development of Apogamic Amoebae From Heterothallic Lines of a Myxomycete, Didymium Iridis

Mulleavy

Collins

1979

American J of Botany

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By making appropriate crosses between heterothallic sexual clones of Didymium iridis we can recover apogamic lines in the F1 generation. In this organism, heterothallic forms typically produce a haploid myxamoebal stage, but recently two diploid myxamoebal clones homozygous for mating types were discovered. When these are crossed, A2A2 x A5A5, tetraploid Plasmodia are produced which later yield diploid F1 meiospores. Sixty‐four percent of the single‐spore‐derived clones produce both myxamoebae and Plasmodia, while the remainder do not progress past the myxamoebal stage. These results are consistent with the predictions that from tetraploid nuclei, mating types should segregate in the meiospores in a ratio of 1A2A2:4A2A5:1A5A5, and that myxamoebae heterozygous, A2A5, for mating type should yield Plasmodia apogamously. As the means for verifying relative ploidy levels of myxamoebae and Plasmodia, nuclear DNA was measured with a scanning microspectrophotometer.

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Nuclear DNA Content and Senescence in Physarum polycephalum

Cited by 25 publications

References 9 publications

Sclerotization in Relation to Plasmodial Senescence in the Acellular Slime Mould Didymium iridis

Sclerotization in Relation to Plasmodial Senescence in the Acellular Slime Mould Didymium iridis

Flow cytometry reveals a high degree of genomic size variation and mixoploidy in various strains of the acellular slime mold Physarum polycephalum

Development of Apogamic Amoebae From Heterothallic Lines of a Myxomycete, Didymium Iridis

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