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M Sipiczki

Publications and source records attributed to M Sipiczki.

52 records · Page 3Linked to original sources
PubMed1994

Osmotolerant yeasts isolated from Tokaj wines.

Yeasts growing in "Tokaj Aszu" wine and in "Aszu essence" were isolated and characterised. They proved to be physiological races of Saccharomyces cerevisiae and showed high osmotolerance, which was an inherited feature rather than the result of adaptation. No correlations were found between the osmotolerance and the ethanol tolerance or the cell size and morphology. Yeasts in "Aszu essence" are usually undesirable contaminants that impair the quality of the essence. The isolate characterized in this work exhibited physiological parameters very similar to those of the "Tokaj Aszu" strain, which make it a potent competitor of other yeasts in Aszu fermentation. However, the high termo sensitivity of its cells offers a possibility to eliminate them selectively.

Ethanol↗
PubMed1993

Caffeine tolerance in Schizosaccharomyces pombe: physiological adaptation and interaction with theophylline.

Caffeine at concentrations of 8 mM or higher inhibited cell propagation and killed a fraction of the population. Cell inactivation increased incrementally with increasing concentrations. The survivors developed tolerance by physiological adaptation that enabled them to propagate in the presence of the drug, but the tolerance could easily be lost if the cells grew in the absence of caffeine for a few generations. Theophylline was found to diminish the toxic effect of caffeine. Possible mechanisms for the observed cellular response and its implications for studies of the effects of these drugs in eukaryotes are discussed.

Adaptation, Physiological↗
PubMed1993

Mycelial and syncytial growth in Schizosaccharomyces pombe induced by novel septation mutations.

Mutation in the gene sep1+ of the unicellular fission yeast Schizosaccharomyces pombe impairs cell separation after cytokinesis and confers a branching mycelial morphology. The mutant is not defective in cell wall beta-glucanase activity but shows increased sensitivity to Ca2+ and Mg2+, and increased resistance to the microtubule inhibitor benomyl. The mycelial growth of sep1-1 provides a convenient method for the examination of the polar growth pattern and for pedigree analysis as demonstrated by the segregation of mating types in the homothallic microhyphae. sep1 is closely linked to ade1 (0.94 cM) on the right arm of chromosome II. The ts mutation spl1-1 confers a bent cell shape and causes aberrant septum formation at the restrictive temperature. sep1+ and spl1+ perform closely related functions as their mutant alleles interact with each other and with another septation mutant cdc4-8. These functions may overlap with certain cytoskeletal processes and with the determination of cell polarity because the triple mutant forms huge multinucleate syncytia with promiscuous branching and rare septum formation.

Alleles↗
PubMed1991

Sterile UGA nonsense mutants of fission yeast.

Eight sterile mutants, which regain their fertility upon reactivation of an inactivated UGA suppressor allele of the serine tRNA gene sup3, are shown to carry UGA nonsense alleles of two established ste genes, ste1 (one mutant) and ste6 (two mutants), and of two novel genes, ste9 (four mutants) and ste10 (one leaky mutant of ras1-/ste5-like cell morphology). The mutant alleles of ste1 and ste9 lead to a defect in both conjugation and meiosis, whereas those of ste6 and ste10 affect mating only. Two of the four genes map to chromosome I, ste1 in the left arm 6 cM distal of ura1, and ste9 in the right arm 3 cM distal of ade2. The ste10 and ste6 genes are located in the right arms of chromosomes II and III, respectively, the former 4 cM distal of trp1 and the latter 1 cM proximal or distal of trp3.

Alleles↗
PubMed1991

Pheromone production and response in sterile mutants of fission yeast.

Genetically heterothallic strains of various sterile mutants were assayed for residual production of the corresponding mating pheromone as well as responsiveness towards the opposite pheromone. No sexual activities were detected in ste11 strains (previously referred to as aff1 or steX, which we show are allelic), whilst the production of M factor was unaffected by ste1 to ste10 mutations. P factor production was still possible in class I ste mutants (ste5, ste6 and ste10), which also allow meiosis in diploid strains. With the exception of the leaky ste10-F23 mutant, no changes in cell morphology were induced by exposure to the opposite pheromone in the ste mutant strains.

Alleles↗
PubMed1991

Common genes and pathways in the regulation of the mitotic and meiotic cell cycles of Schizosaccharomyces pombe.

Cell division cycle mutants defective in G1, DNA replication or nuclear division were tested for sporulation at semi-restrictive temperatures. In cdc1-7, cdc5-120, cdc17-L16 and cdc18-46 no abnormalities were observed; cdc10-129, cdc20-M10, cdc21-M6B, cdc23-M36 and cdc24-M38 formed four-spored asci but with a low efficiency; cdc22-M45 was completely defective in meiosis, but could conjugate and formed zygotes with a single nucleus. Mutants defective in the mitotic initiation genes cdc2, cdc25 and cdc13 were blocked in meiosis II. None of the wee1-50, adh.nim1+ and win1+ alleles had any affect on sporulation, suggesting that their interactions with cdc25 and cdc2 are specific to mitosis. The meiotic function of cdc13 is TBZ-sensitive and probably exerted downstream of cdc2. Single mutants in cut1 or cut2 did not effect sporulation, whereas the double mutant cut1 cut2 formed two-spored asci. The results demonstrate that the cell division cycle and the meiotic developmental pathway share common genes and regulatory cascades.

Genes, Fungal↗
PubMed1990

Dissociation of meiotic and mitotic roles of the fission yeast cdc2 gene.

The fission yeast cdc2 gene is pleiotropic, functioning both in the cell division cycle and in meiosis. Here we show that cdc2 is allelic to tws1, a previously isolated meiotic gene. Dissociation of meiotic and mitotic roles of the gene is also demonstrated by finding mutant alleles specifically altered in only one of the two processes.

Alleles↗
PubMed1988

The role of sterility genes (ste and aff) in the initiation of sexual development in Schizosaccharomyces pombe.

Haploid homothallic strains of Schizosaccharomyces pombe with mutations in any of nine "sterility genes" (ste) do not mate with wild-type fertile strains. Those defective in genes ste1 to ste4 and ste7 to ste9 are also deficient in meiosis and sporulation. I found that the ste1, ste3 and ste8 genes act very early in the sexual development, presumably before the pat1-controlled conjugation-specific event. ste5 and ste6 exert their function downstream of pat1 in the initiation of conjugation and do not play any role in the meiotic pathway. ste2, ste4, ste7 and ste9 are involved in both sexual pathways: they seem to act downstream of pat1 in conjugation but upstream of pat1 in the initiation of meiosis. A new gene, aff1, whose defective allele suppresses the pat1-114-provoked haploid sporulation and arrest of vegetative growth is also described. It is supposed that the aff1+ gene product participates in a cascade of regulatory events, as a factor antagonistic to pat1.

Alleles↗
PubMed1986

Replicating plasmids in Schizosaccharomyces pombe: improvement of symmetric segregation by a new genetic element.

We characterized a number of widely used yeast-Escherichia coli shuttle vectors in the fission yeast Schizosaccharomyces pombe. The 2 micron vectors pDB248 and YEp13 showed high frequency of transformation, intermediate mitotic and low meiotic stability, and a low copy number in S. pombe, analogous to their behavior in [cir0] strains of Saccharomyces cerevisiae. The S. cerevisiae integration vectors pLEU2 and pURA3 transformed S. pombe at very low frequencies but, surprisingly, in a nonintegrative fashion. Instead, they replicated autonomously, and they showed very high copy numbers (up to 150 copies per plasmid-containing cell). This could reflect a lack of sequence specificity for replication of plasmid DNA in S. pombe. pFL20, an S. pombe ars vector, and a series of plasmids derived from it were studied to analyze the unusually high stability of this plasmid. Mitotic stability and partitioning of the plasmids was measured by pedigree analysis of transformed S. pombe cells. An S. pombe DNA fragment (stb) was identified that stabilizes pFL20 by improvement of plasmid partitioning in mitosis and meiosis.

DNA Restriction Enzymes↗
PubMed1985

Morphological and colour mutants of Trichoderma viride: characterization and complementation.

A total of 26 morphological and colour mutants of Trichoderma viride were characterized. They were divided into three groups based on morphology, pigmentation, growth rates and intensity of conidiation. Complementation analysis of colour mutants and mutants with disturbances in conidiation showed that after anastomosis and protoplast fusion only heterokaryotes are formed while no nuclear migration and diploidization takes place.

Diploidy↗
PubMed1980

Genetical analysis of a sterile mutant by protoplast fusion in the fission yeast Schizosaccharomyces pombe.

The genetical analysis, by protoplast fusion, of the sterile strain ED22 of Schizosaccharomyces pombe is described. Two major mutations are harboured by this strain. One, cdc 25.22, is conditionally defective in mitosis. The other mutation, ste 1.1, causes sterility in strains of h-, h+ or mat 2.102 mating-type. Sterility is due to the failure of cell agglutination. We present evidence that ste 1.1 is defective in the production of a non-diffusible and non-mating-type specific factor. ste 1 and cdc 25 both map on chromosome I and are loosely linked.

Agglutination↗
PubMed1980

Characterization of conidiation mutants in Trichoderma viride by hyphal anastomosis and protoplast fusion.

Conidiation mutants were isolated from the fungus Trichoderma viride, and tested for complementation by both anastomosis and protoplast fusion. They could be grouped into three classes: (1) colour mutants; (2) mutants with reduced conidiation; and (3) nonconidiating mutants. Several mutants of classes (2) and (3) were incapable of anastomosis, but via protoplast fusion they produced heterokaryons suitable for complementation tests.

Genetic Complementation Test↗
PubMed1979

Morphogenic effect of 2-deoxy-D-arabino-hexose on Rhodosporidium toruloides.

The presence of 2-deoxy-D-arabino-hexose in the growth medium caused marked morphological changes in the cells of Rhodosporidium toruloides. The originally elongated ellipsoidal cells grew spherically in the presence of the deoxy-sugar, displayed differences in cell division and separation, and were larger than the control cells. After exhaustion of glucose from the medium the cells died, although no lysis was observed. The morphological changes were accompanied by significant alterations in the carbohydrate composition of the cell wall. The wall of R. toruloides grown in the presence of the deoxy-sugar contains higher proportions of chitin and glucan, while the relative contents of mannose and galactose polymers decreased drastically in comparison to normal cells.

Basidiomycota↗
PubMed1977

Protoplast fusion of Schizosaccharomyces pombe Auxotrophic mutants of identical mating-type.

Protoplasts of methionine- and lysine-requiring h- mutants isolated from the L972 h- strain of Schizosaccharomyces pombe were fused. The protoplasts were obtained from the cells with enzymes produced by Trichoderma viride. When a mixture of the protoplasts was treated with 30% PEG 4000 solution containing 10 mM CaCl2, cell fusion and complementation was attained with a frequency of 0.17%. Both fusion partners were recovered among the spores after crossing of the fusion products with the strain M210 ade6 h+. Cytological and haploidization examinations showed that the fusion cells are not heterokaryons, and that the increased amount of genetic material is situated in one nucleus.

Ascomycota↗
PubMedDate not supplied

Polyploidy in the haplontic yeast Schizosaccharomyces pombe: construction and analysis of strains.

The fission yeast Schizosaccharomyces pombe has a haplontic life cycle in which the diplophase is confined to the zygote. Through the use of one- and two-step protoplast fusions we show that the ploidy can be increased up to pentaploid. The polyploid fusion products are rather unstable and segregate cells of lower ploidies by gradual loss of chromosomes during mitotic divisions. The polyploid cells conjugate normally but are prone to arrest at various stages of meiosis (1-, 2- and 3-spored asci, binucleate spores) and/or produce inviable, most probably aneuploid, spores. Marker segregation in the complete tetrads indicates the multiple association of homologous chromosomes. In tetra- and penta-ploid meiosis, multispored (6- to 7-spored) asci are also produced, probably by postmeiotic division of the nuclei.

Cloning, Molecular↗