Summary
In Saccharomyces cerevisiae, diploid strains which are respiratory deficient (e.g., rho−) or are homozygous for the mating-type locus (i.e., either a/a or α/α) are unable to sporulate. In order to induce sporulation in these nonsporulating strains, the technique of protoplast fusion mediated by polyethylene glycol was adopted. In this study, the products of protoplast fusion were induced to sporulate without reversion to normal cells.
Protoplasts from a respiratory-deficient diploid strain were mixed with those from a respiratory-competent haploid one carrying mitochondrial drug resistance markers, treated with 30% polyethylene glycol-4000 and 25 mM CaCl2, and incubated in 0.1 M potassium acetate containing 0.8 M sorbitol as an osmotic stabilizer. After two days' incubation, asci with three to eight spores were formed at a frequency of 1×10−3 to 2×10−4. Sporulation was also observed in products of fusion between an a/a diploid and α haploid strains and between an α/α diploid and a haploid strains. The analysis of the genotypes of spores revealed that when fusion products were cultured under conditions for sporulation, karyogamy did not take place, diploid nuclei underwent meiosis, and both diploid and haploid nuclei were able to develop into spores.
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References
Arima K, Takano I (1979) Multiple fusion of protoplasts in Saccharomyces yeasts. Mol Gen Genet 173:271–277
Eddy AA, Williamson DH (1959) Formation of aberrant cell wall and of spores by the growing yeast protoplast. Nature 183:1101–1104
Ephrussi B (1953) Nucleo-cytoplasmic relations in microorganisms. Clarendon Press, Oxford
Fournier P, Provost A, Bourguignon C, Heslot H (1977) Recombination after protoplast fusion in the yeast Candida tropicalis. Arch Microbiol 115:143–149
Gunge N, Tamaru A (1978) Genetic analysis of products of protoplast fusion in Saccharomyces cerevisiae. Japan J Genet 53:41–49
Kao KN, Michayluk MR (1974) A method for high frequency intergeneric fusion of plant protoplasts. Planta 115:355–367
Klar AJS (1980) Mating-type functions for meiosis and sporulation in yeast act through cytoplasm. Genetics 94:597–605
Maráz A, Kiss M, Ferenczy L (1978) Protoplast fusion in Saccharomyces cerevisiae strains of identical and opposite mating types. FEMS Microbiol Lett 3:319–322
Mortimer RK, Hawthorne DC (1969) Yeast genetics. In: Rose AH, Harrison JS (eds) The yeasts, vol. 1. Academic Press Inc, London and New York, p 385
Nečas O (1971) Cell wall synthesis in yeast protoplasts. Bacteriol Rev 35:149–170
Perkins DD (1949) Biochemical mutants in the smut fungus Ustilago maydis. Genetics 34:607–626
Roman H, Sands SM (1953) Heterogeneity of clones of Saccharomyces derived from haploid ascospores. Proc Natl Acad Sci USA 39:171–179
Sherman F, Fink GR, Lawrence CW (1971) Methods in yeast genetics. Cold Spring Harbor Laboratory, New York
Sipiczki M, Ferenczy L (1977) Protoplast fusion of Schizosaccharomyces pombe auxotrophic mutants of identical mating-type. Mol Gen Genet 154:77–81
Takano I, Arima K (1979) Evidence of insensitivity of the α-inc allele to the function of the homothallic genes in Saccharomyces yeasts. Genetics 91:245–254
Tsuboi M (1981) Sporulation of spheroplast in Saccharomyces cerevisiae. Plant Cell Physiol 21:59–63
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Communicated by CH. Auerbach
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Tsuboi, M. Sporulation of products of protoplast fusion without regeneration in Saccharomyces cerevisiae . Molec. Gen. Genet. 182, 1–6 (1981). https://doi.org/10.1007/BF00422758
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DOI: https://doi.org/10.1007/BF00422758