A Gene, ALCA, Affecting the Life Cycle Form Expressed in PHYSARUM POLYCEPHALUM (original) (raw)
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Mutants with decreased differentiation to plasmodia in Physarum polycephalum
MGG Molecular & General Genetics, 1977
Mutant ("APT") amoebae that display reduced ability to form plasmodia asexually were isolated by the use of an enrichment procedure. The results of reconstruction experiments show that the procedure enriches only for mutants blocked early in the pathway from amoeba to plasmodium. Mutants were isolated from four parents, two of which produce plasmodia asexually because they carry the allele ruth of the mating type locus, and two because they carry gad (greater asexual differentiation) mutations. The APT mutants varied widely in the frequency of residual plasmodium formation, which occurred, in some cases, by reversion. The mutants, called apt (amoeba to plasmodium transition), were recessive in diploids and linked to the mating type (mr) locus. Mutants derived from the gad parents, unlike the parents themselves, crossed readily with heterothallic amoebae. Progeny analysis from such crosses indicates that both gad mutations are linked to mt. The mutants derived from one of the ruth parents fell into two groups on the basis of their ability to cross with the mutants derived from the rot2 gad-8 parent. The result suggests that the ruth-derived mutants represent two or more complementation groups. Mutants derived from the rot2 gad-8 parent cross with rot2 amoebae and hence display an altered mating specificity.
The sexual type of plasmodia formation, termed crossing, occurs only in mixtures of unlike amoebae and is regulated by two unlinked multiallelic mating-type loci, matA (that affects the differentiation of the fusion products into plasmodia) and rnatB (that affects the amoeba1 fi1sio11 step of crossing). In the present study, complementation tests were carried out setting up crossing tests among the forty new npf mutants of f. polvcerhulum (Wadaan, 2003) for evidence of the stage at which development was blocked. Twelve strains fa~lqd to form binucleate cells and the remaining 28 strains all formed binuckge cells. Colnplementation tests were carried out by_@xing each of the 40 new mutants with tester strains carrying knoqi&npf mutations. Out of 40 mutants isolated, 26 were assigned to not;@# than 17 complementation groups, twelve of which were previousIy,t&nown. The crosses were heteroallelic for matB to ensure that a m o b l . fusion occurred with high frequency. Complementation tes...
A Third Multiallelic Mating-type Locus in Physarum polycephalum
Microbiology, 1987
Sexual development (crossing) in Physarum polycephafum occurs when two haploid amoebae fuse to form a diploid plasmodium. The imz locus influences the maximum pH at which crossing can occur. A new allele of imz has been identified, bringing the total number of alleles to three. Contrary to earlier findings, it has been shown that all homoallelic combinations of imz alleles display a similar pH limit for crossing, which is lower than that for imz-heteroallelic combinations. It is concluded that imz is a mating compatibility locus; thus the mating-type system of P. pofycephafum comprises three multiallelic loci : matA, matB and imz. It is proposed that imz be renamed matC.
A developmental mutation (npfL1) resulting in cell death in Physarum polycephalum
Journal of general microbiology, 1992
In Physarum, microscopic uninucleate amoebae develop into macroscopic multinucleate plasmodia. In the mutant strain, RA614, plasmodium development is blocked. RA614 carries a recessive mutation (npfL1) in a gene that functions in sexual as well as apogamic development. In npfL+ apogamic development, binucleate cells arise from uninucleate cells by mitosis without cytokinesis at the end of an extended cell cycle. In npfL1 cultures, apogamic development became abnormal at the end of the extended cell cycle. The cells developed a characteristic rounded, vacuolated appearance, nuclear fusion and vigorous cytoplasmic motion occurred, and the cells eventually died. Nuclei were not visible by phase-contrast microscopy in most of the abnormally developing cells, but fluorescence microscopy after DAPI staining revealed intensely staining, condensed nuclei without nucleoli. Studies of tubulin organization during npfL1 development indicated a high frequency of abnormal mitotic spindles and, in...
Temperature-sensitive mutants of Physarum polycephalum: viability, growth, and nuclear replication
Journal of Bacteriology, 1979
Using a selfing strain of Physarumpolycephalum that forms haploid plasmodia, we have isolated temperature-sensitive growth mutants in two ways. The negative selectant, netropsin, was used to enrich for temperature-sensitive mutants among a population of mutagenized amoebae, and, separately, a nonselective screening method was used to isolate plasmodial temperature-sensitive mutants among clonal plasmodia derived from mutagenized amoebae. Complementation in het
Temperature-sensitive mutants of the slime mould Physarum polycephalum
Molecular and General Genetics, 1976
Methods are described for the isolation and testing of temperature-sensitive plasmodial strains of Physarum polycephalum. Nineteen temperature-sensitive strains were found by screening plasmodia derived from mutagenised amoebae and the properties of these are described. A scheme is outlined for the detection of specific mitotic cycle lesions amongst temperature-sensitive strains, and the properties of a presumptive mitotic cycle mutant are described.
Variable pathways for developmental changes of mitosis and cytokinesis in Physarum polycephalum
The Journal of Cell Biology, 1991
The development of a uninucleate ameba into a multinucleate, syncytial plasmodium in myxomycetes involves a change from the open, astral mitosis of the ameba to the intranuclear, anastral mitosis of the plasmodium, and the omission of cytokinesis from the cell cycle. We describe immunofluorescence microscopic studies of the amebal-plasmodial transition (APT) in Physarum polycephalum. We demonstrate that the reorganization of mitotic spindles commences in uninucleate cells after commitment to plasmodium formation, is completed by the binucleate stage, and occurs via different routes in individual developing cells. Most uninucleate developing cells formed mitotic spindles characteristic either of amebae or of plasmodia. However, chimeric mitotic figures exhibiting features of both amebal and plasmodial mitoses, and a novel star microtubular array were also observed. The loss of the ameba-specific alpha 3-tubulin and the accumulation of the plasmodium-specific beta 2-tubulin isotypes d...
Induction of somatic fusion and heterokaryosis in two incompatible strains of Physarum polycephalum
Developmental Biology, 1974
These studies describe a method for the induction of somatic fusion and production of heterokaryons between two incompatible strains of the myxomycete Physarum polycephalum. It was shown that plasmodia disrupted into small nucleated pieces by homogenization undergo fusion and plasmoidal reorganization when incubated under defined conditions. Homogenization and reorganization of two incompatible strains of P. polycephalum resulted in the formation of some heterokaryotic plasmodia which showed the characteristic nuclei of both original strains. Analysis of the fusion characteristics of the reorganized plasmodia and the original strains indicated that the genes which control somatic compatibility were expressed in both nuclear types within the heterokaryotic plasmodia. These studies support the hypothesis that somatic fusion is controlled at the level of the plasmodial surface.