Mating type and the differentiated state in Physarum polycephalum

Adler, Paul N.; Holt, Charles E.

doi:10.1016/0012-1606(75)90024-x

Cited by 40 publications

(29 citation statements)

References 30 publications

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“…It is clear from these results, as well as from previous studies [23], that selfed plasmodium formation can occur in the absence of stable mutation. Although illegitimate plasmodia were predominant only in the set of spontaneously arising plasmodia of LU648, it is apparent that the frequencies of selfed plasmodia given in Table 3 do not necessarily represent mutant frequencies.…”

Section: Analysis Of Selfed Plasmodiamentioning

confidence: 52%

Mutations affecting the initiation of plasmodial development in Physarum polycephalum

1979

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In the heterothallic myxomycete Physarum polycephalum, uninucleate amoebae normally differentiate into syncytial plasmodia following heterotypic mating. In order t o study the genetic control of this developmental process, mutations affecting the amoebal-plasmodia1 transition have been sought. Numerous mutants characterized by self-fertility have been isolated. The use of alkylating mutagens increases the mutant frequency over the spontaneous level but does not alter thc mutant spectrum. Three spontaneous and 14 induced mutants have been analyzed genetically. In each, the mutation appears to be linked to the mating type locus. In three randomly selected mutants, the nuclear DNA content is the same in amoebae and plasmodia, indicating that amoebal syngamy does not precede plasmodium development in these strains. These results indicate that a highly specific type of mutational event, occurring close to or within the mating type locus, can abolish the requirement for syngamy normally associated with plasmodial differentiation. These mutations help define a genomic region regulating the switch from amoebal to plasmodial growth.

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Section: Analysis Of Selfed Plasmodiamentioning

confidence: 52%

Mutations affecting the initiation of plasmodial development in Physarum polycephalum

1979

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“…Owing to the organization of the repeated sequences in the central spacer (8) (Fig. 1 (2). Such diploid progeny are believed to result from the meiotic division of occasional tetraploid nuclei found in the predominantly diploid plasmodia (2,15).…”

Section: Methodsmentioning

confidence: 99%

“…1 (2). Such diploid progeny are believed to result from the meiotic division of occasional tetraploid nuclei found in the predominantly diploid plasmodia (2,15). Thus, we do not attribute special significance to this clone.…”

Section: Methodsmentioning

confidence: 99%

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Inheritance of extrachromosomal rDNA in Physarum polycephalum.

Ferris¹,

Vogt²,

Truitt³

1983

Mol. Cell. Biol.

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In the acellular slime mold Physarum polycephalum, the several hundred genes coding for rRNA are located on linear extrachromosomal DNA molecules of a discrete size, 60 kilobases. Each molecule contains two genes that are arranged in a palindromic fashion and separated by a central spacer region. We investigated how rDNA is inherited after meiosis. Two Physarum amoebal strains, each with an rDNA recognizable by its restriction endonuclease cleavage pattern, were mated, the resulting diploid plasmodium was induced to sporulate, and haploid progeny clones were isolated from the germinated spores. The type of rDNA in each was analyzed by blotting hybridization, with cloned rDNA sequences used as probes. This analysis showed that rDNA was inherited in an all-or-nothing fashion; that is, progeny clones contained one or the other parental rDNA type, but not both. However, the rDNA did not segregate in a simple Mendelian way; one rDNA type was inherited more frequently than the other. The same rDNA type was also in excess in the diploid plasmodium before meiosis, and the relative proportions of the two rDNAs changed after continued plasmodial growth. The proportion of the two rDNA types in the population of progeny clones reflected the proportion in the parent plasmodium before meoisis. The rDNAs in many of the progeny clones contained specific deletions of some of the inverted repeat sequences at the central palindromic symmetry axis. To explain the pattern of inheritance of Physarum rDNA, we postulate that a single copy of rDNA is inserted into each spore or is selectively replicated after meiosis.In some lower eucaryotic organisms, the multiple genes coding for rRNA are located on extrachromosomal DNA molecules. In the best studied of these systems, Tetrahymena species (ciliates) and Physarum polycephalum (an acellular slime mold), the extrachromosomal rDNAs are of a discrete size (about 20 and 60 kilobases [kb], respectively) and have a similar structure. The molecules are linear and are organized as palindromes, with two transcription units arranged in opposite orientations near the ends of the DNA, separated by a spacer region with a rotational symmetry axis in the middle (13, 21). In P. polycephalum rDNA this spacer is 20 kb in size and contains a complex series of directly repeated, inversely repeated, and unique sequences (8). Replication of P. polycephalum rDNA molecules (22) commences at one of four potential origins in the central spacer region and proceeds bidirectionally towards the ends of the linear molecules. In contrast to chromosomal DNA replication, rDNA replication takes place during most of the mitotic cycle, notjust in the S phase, and is unscheduled. That is, some rDNA molecules replicate once, some more than once, and some not at all, with the end result being that the total number of molecules after each mitosis is unchanged. The ends of the linear P. polycephalum rDNA molecules are heterogeneous in size, and near each end are located onenucleotide gaps on one strand at specific nucleotide seq...

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“…Holt's laboratory at the Massachusetts Institute of Technology, Cambridge, Mass. After several years of culture in this lab, it was observed that the C1 stock was heterogeneous, and rapidly and slowly differentiating variants were isolated [21]. At the time it was thought that the slow variant had the same phenotype as the original C1 strain of Cooke and Dee [4]; the slow variant was thus called C1, and the rapid variant was named CH357.…”

Section: Discussionmentioning

confidence: 98%

Food deprivation is not a prerequisite for the amoebal to plasmodial transition in Physarum polycephalum

1983

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The effect of food supply on the onset of asexual and sexual plasmodium formation in Physarum polycephalum was studied. Asexual differentiation occurs readily in amoebae carrying the m t A h mating type allele. The density at which these amoebae begin to differentiate is influenced by the ind locus, which controls the production of a diffusible inducer. The alleles ind-1 and ind-2 are known. Strains carring the ind-I allele begin plasmodium formation at a low amoebal density (rapid differentiation), while strains carring the i d -2 allele differentiate at a higher amoebal density (slow differentiation). The onset of differentiation is characteristic of the strain and did not change with a 20-fold variation in the number of food bacteria available. Sexual differentiation occurs between compatible amoebal strains. For a given pair of amoebal strains the onset of plasmodium formation occurs at a characteristic cell density that is determined by the genetic backgrounds of the strains. The ind locus is one of the genes that influences this cell density. Plasmodia are formed at a lower cell density in crosses involving compatible amoebae carrying the ind-l allele than they are in crosses with strains carrying the ind-2 allele. As was found for asexual differentiation, an approximate 20-fold variation in the food supply did not affect the initiation of sexual plasmodium formation. These results suggest that in most cases starvation does not trigger the differentiation of amoebae into plasmodia. The time of onset of plasmodium formation is determined largely by genetic factors.

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Mating type and the differentiated state in Physarum polycephalum

Cited by 40 publications

References 30 publications

Mutations affecting the initiation of plasmodial development in Physarum polycephalum

Mutations affecting the initiation of plasmodial development in Physarum polycephalum

Inheritance of extrachromosomal rDNA in Physarum polycephalum.

Food deprivation is not a prerequisite for the amoebal to plasmodial transition in Physarum polycephalum

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