Evidence for the existence of elements of a para-sexual cycle in the cellular slime mould,
            <i>Dictyostelium discoideum</i>

Sinha, Umakant; Ashworth, J.

doi:10.1098/rspb.1969.0075

Cited by 32 publications

(12 citation statements)

References 5 publications

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“…Indeed, these cultures give plating efficiencies of greater than 95% which suggests that the proportion of cells with less than the haploid chromosonie number is rather small. Aneuploid amoebae with chromosome numbers between seven and I 4 presumably represent transient intermediates in the process of haploidization of diploid nuclei (Sinha & Ashworth, 1969;Brody & Williams, 1974). The data presented here indicate that diploids are found at a frequency of no more than 2%.…”

Section: Discussionmentioning

confidence: 61%

Analysis of Karyotype and Ploidy of Dictyostelium discoideum Using Colchicine-induced Metaphase Arrest

Hames

1977

Journal of General Microbiology

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SUMMARYConditions for obtaining colchicine-induced metaphase arrest of the chromosomes of the cellular slime mould Dictyostelium discoideum are described. Using this technique, which increases the mitotic index of exponentially growing amoebae from 1.5 to I I%, it has been demonstrated conclusively that D. discoideum has a haploid chromosome number of seven and that strain AX^ (ATCC24397) is not highly aneuploid as has recently been suggested. Each of the seven chromosomes can be identified by a characteristic banding pattern seen after staining with Giemsa.

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Section: Discussionmentioning

confidence: 61%

Analysis of Karyotype and Ploidy of Dictyostelium discoideum Using Colchicine-induced Metaphase Arrest

Hames

1977

Journal of General Microbiology

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“…Our own results and those published in the earlier studies indicate that segregants haploid for any one marker are haploid for all others. Thus, if haploidization proceeds via progressive losses of chromosomes as observed in Aspergillus (9)-and suggested for Dictyostelium (4), the aneuploid derivatives must be quite unstable. The exceptional class of diploid segregants encountered in the cross M28 x TS12 does seem to indicate that differential chromosome losses do occur and that aneuploidal instability can result in reattainment of the diplophase rather than further loss of chromosomes.…”

Section: Discussionmentioning

confidence: 99%

“…However, the low frequencies of karyogamy and segregation made the method impractical for routine use in the absence of selective techniques. The existence of parasexuality in this species has since been confirmed (3,4). However, the conditions used yielded only unstable heterozygotes, which disappeared within a few generations and could not conveniently be used for segregation studies.…”

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confidence: 99%

Parasexual Recombination in Dictyostelium discoideum: Selection of Stable Diploid Heterozygotes and Stable Haploid Segregants

Katz

Sussman

1972

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

109

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Haploid strains of Dictyostelium discoideum bearing temperature-sensitive mutations have been used to select stable diploid, heterozygotic clones, which arise at low frequency (about . Segregants arise from such diploids at low frequency (about 10-3). The diploids were heterozygous for resistance to cycloheximide and were phenotypically sensitive to the drug. Growth of the diploid cells in the presence of cycloheximide automatically selected those segregants bearing the resistant allele, and facilitated examination of the assortment of unselected markers. The combination of the two selective methods provides a workable system of genetic analysis in this species. We have used this method to locate six markers on three different linkage groups.In Dictyostelium discoideum, ploidy is an inherited condition. Three kinds of strains have been isolated: stable haploid, stable diploid, and metastable. (All clones of the last type contained both haploid and diploid cells.) Each of the varieties could be isolated from the others (1, 2).At least some diploid clones arose by cell fusion and karyogamy. Two haploid strains, marked with mutations affecting the color of the fruiting bodies, were grown in mixed culture and yielded at very-low frequency stable, diploid, doubly heterozygous clones. On continued passage the latter, in turn, yielded at very-low frequency stable haploid segregants, including all four of the expected parental and recombinant phenotypes. However, the low frequencies of karyogamy and segregation made the method impractical for routine use in the absence of selective techniques. The existence of parasexuality in this species has since been confirmed (3, 4). However, the conditions used yielded only unstable heterozygotes, which disappeared within a few generations and could not conveniently be used for segregation studies.A first step in the direction of providing a practical routine system was taken by Loomis (5), who isolated temperaturesensitive mutants of D. discoideum. Pairs of mutants were mixed and incubated at the permissive temperature, and were then plated out on nutrient agar at the restrictive temperature. Clones of temperature-resistant recombinants were thereby selected. Unfortunately, only unstable diploid heterozygotes were encountered, and they could not be isolated and retained for quantitative study.In this paper, we report a series of crosses from which stable diploid, heterozygotic clones were obtained. Temperature-sensitive haploid parents bearing additional outside markers were used. A method has been devised whereby the rare haploid segregants from such diploids are automatically selected. Together, the two selective methods provide the basis for a workable system of genetic analysis used here to follow the segregation and recombination of six markers. Three linkage groups have been identified thus far. MATERIALS AND METHODSIsolation of Temperature-Sensitive Mutants. Strains derived from D. discoideum NC4 (haploid) were grown on SM agar in association with Aerobacter aeroge...

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“…In this cycle haploid amoebae of two strains occasionally fuse to form heterozygous diploids that slowly and spontaneously revert to the haploid state with random segregation of the two sets of chromosomes (Sinha & Ashworth, 1969;Brody & Williams, 1974). This cycle allows complementation and linkage studies to be made (Pontecorvo & Kafer, I 958 ; Katz & Sussman,I 972).…”

Section: Introductionmentioning

confidence: 99%

“…Unfortunately all reports so far, except one (Fukui & Takeuchi, 1971), indicate that resistance to a wide range of drugs tested is recessive (Sinha & Ashworth, 1969 ;Katz & Sussman, 1972;Loomis, 1971 ;Williams et al, 1g74b;Wright, Williams & Newell, unpublished). Diploids formed from pairs of haploids, each resistant to different drugs, are consequently sensitive to both drugs and while this system has been successfully used for selection of haploids from heterozygous diploids (Katz & Sussman, 1972;Williams et al, 1g74b), it cannot generally be used for the initial selection of the diploids.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity to Bacillus subtilis: A Novel System for Selection of Heterozygous Diploids of Dictyostelium discoideum

Newell

Henderson

Mosses

et al. 1977

Journal of General Microbiology

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Evidence for the existence of elements of a para-sexual cycle in the cellular slime mould, Dictyostelium discoideum

Cited by 32 publications

References 5 publications

Analysis of Karyotype and Ploidy of Dictyostelium discoideum Using Colchicine-induced Metaphase Arrest

Analysis of Karyotype and Ploidy of Dictyostelium discoideum Using Colchicine-induced Metaphase Arrest

Parasexual Recombination in Dictyostelium discoideum: Selection of Stable Diploid Heterozygotes and Stable Haploid Segregants

Sensitivity to Bacillus subtilis: A Novel System for Selection of Heterozygous Diploids of Dictyostelium discoideum

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