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In the fission yeast Schizosaccharomyces pombe, the mating reaction is controlled by two mating pheromones, M-factor and P-factor, secreted by M- and P-type cells, respectively. M-factor is a C-terminally farnesylated lipid peptide, whereas P-factor is a simple peptide. To examine whether this chemical asymmetry in the two pheromones is essential for conjugation, we constructed a mating system in which either pheromone can stimulate both M- and P-cells, and examined whether the resulting autocrine strains can mate. Autocrine M-cells responding to M-factor successfully mated with P-factorless P-cells, indicating that P-factor is not essential for conjugation; by contrast, autocrine P-cells responding to P-factor were unable to mate with M-factor-less M-cells. The sterility of the autocrine P-cells was completely restored by expressing the M-factor receptor. These observations indicate that the different chemical characteristics of the two types of pheromone, a lipid and a simple peptide, are not essential; however, a lipid peptide might be required for successful mating. Our findings allow us to propose a model of the differential roles of M-factor and P-factor in conjugation of S. pombe. [ABSTRACT FROM AUTHOR]

When a and α type haploid cells of Saccharomyces cerevisiae were mixed and cultured, deoxyribonucleic acid synthesis was retarded but ribonucleic acid and protein syntheses were not. It was found that culture filtrate of a type cells inhibited deoxyribonucleic acid synthesis of α type cells and that of α type cells inhibited that of a type cells. Thus, sex-specific diffusible substances secreted by opposite mating type cells are thought, at least partly, to be responsible for the retardation of deoxyribonucleic acid synthesis. [ABSTRACT FROM AUTHOR]

Using auxin‐responsive diploid strains of Saccharomyces cerevisiae and S. ellipsoideus, we studied the role of cell wall‐degrading enzymes in the auxin‐induced cell expansion. Highly purified fungal β‐l,3‐glucanase added to cell suspension caused cell expansion in these strains. The cell expansion induced by auxin was inhibited by the addition of õ‐glucono‐lactone, which inhibited the activity of a crude β‐l,3‐gluca‐nase preparation from yeast in a competitive manner. Laminarinase activity was significantly higher in the extract from auxin‐treated yeast cells than in the extract of cells not treated with auxin. These results support the idea that auxin induces expansion of yeast cells of certain strains through enhancement of the activity of wall polysaccharide‐degrading enzymes. [ABSTRACT FROM AUTHOR]

The effect of β-1,3-nlucanase on the cell expansion was studied with diploid strains of Saccharomyceft ellipsoideus and S. cereuisiae, and their mutants differing in the response to auxin. The following results were obtained. Cell expansion was induced by β-l,3-glucanase only in auxin-responsive or potentially auxin-responsive strains. β-1,3-Glucanast' induced cell expansion more rapidly than auxin. The cell wall of the auxin-responsive strain was more susceptible to digestion by β-l,3-glucanase than that of the auxin-unresponsive one. The sensitivity of yeast cells to auxin action is discussed in relation to the nature of cell wall. [ABSTRACT FROM AUTHOR]

The following results were obtained using a variant yeast strain, N55, which can respond to the cell-elongating action of auxin. Base analogs of nucleic acids (2-thiouracli, 8-azaguanine, and 5-fluorouracil) inhibited the auxin-induced elongation of yeast cells only when they were added to the preculture prior to auxin treatment. The inhibitory effect of 2-thiouracil and 5-fluorouracil was reversed by uracil and that of 8-azaguanine by guanine. Actinomycin D inhibited the auxin-induced elongation when given to the culture containing auxin, but not when given to the preculture. The similarity in these respects between yeast and tissues of higher plants is discussed. [ABSTRACT FROM AUTHOR]

Yeast cells producing mammalian-type N-linked oligosaccharide show severe growth defects and the decreased protein productivity because of the disruption of yeast-specific glycosyltransferases. This decreased protein productivity in engineered yeast strains is an obstacle to the development of efficient glycoprotein production in yeast. For economic and effective synthesis of such therapeutic glycoproteins in yeast, the development of appropriate strains is highly desirable. We applied a novel mutagenesis technique that utilized the proofreading-deficient DNA polymerase δ variant encoded by the pol3-01 gene of Saccharomyces cerevisiae or the cdc6-1 gene of Schizosaccharomyces pombe to the engineered S. cerevisiae TIY20 strain and S. pombe KT97 strain, respectively. TIY20, which is deficient in the outer chain of mannan due to the disruption of three genes (och1Δ, mnn1Δ, mnn4Δ), and KT97, which is an och1 disruptant, are impractical as hosts for the production of therapeutic glycoproteins since they show a temperature-sensitive (ts) phenotype, a growth defect phenotype, and decreased protein productivity. We successfully isolated YAB mutants that alleviated the growth defect of the TIY20 strain. Surprisingly, these mutants generally secreted foreign proteins better than the wild-type strain. Furthermore, we successfully isolated YPAB mutants that alleviated the growth defect of the KT97 strain, too. The development of these new mutants by the combination of genetic engineering of yeast and this mutagenesis technique are major breakthroughs for the production of therapeutic glycoproteins in engineered yeast cells. [ABSTRACT FROM AUTHOR]