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Pheromone-regulated genes required for yeast mating differentiation.

Erdman S, Lin L, Malczynski M, Snyder M - J. Cell Biol. (1998)

Bottom Line: Transposon insertion alleles corresponding to 20 genes that are novel or had not previously been known to be pheromone regulated were examined for effects on the mating process.Mutations in four novel genes, FIG1, FIG2, KAR5/ FIG3, and FIG4 were found to cause mating defects.Our results indicate that a variety of novel genes are expressed specifically during mating differentiation to mediate proper cell morphogenesis, cell fusion, and other steps of the mating process.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Yale University, New Haven, Connecticut 06520-8103, USA.

ABSTRACT
Yeast cells mate by an inducible pathway that involves agglutination, mating projection formation, cell fusion, and nuclear fusion. To obtain insight into the mating differentiation of Saccharomyces cerevisiae, we carried out a large-scale transposon tagging screen to identify genes whose expression is regulated by mating pheromone. 91,200 transformants containing random lacZ insertions were screened for beta-galactosidase (beta-gal) expression in the presence and absence of alpha factor, and 189 strains containing pheromone-regulated lacZ insertions were identified. Transposon insertion alleles corresponding to 20 genes that are novel or had not previously been known to be pheromone regulated were examined for effects on the mating process. Mutations in four novel genes, FIG1, FIG2, KAR5/ FIG3, and FIG4 were found to cause mating defects. Three of the proteins encoded by these genes, Fig1p, Fig2p, and Fig4p, are dispensible for cell polarization in uniform concentrations of mating pheromone, but are required for normal cell polarization in mating mixtures, conditions that involve cell-cell communication. Fig1p and Fig2p are also important for cell fusion and conjugation bridge shape, respectively. The fourth protein, Kar5p/Fig3p, is required for nuclear fusion. Fig1p and Fig2p are likely to act at the cell surface as Fig1:: beta-gal and Fig2::beta-gal fusion proteins localize to the periphery of mating cells. Fig4p is a member of a family of eukaryotic proteins that contain a domain homologous to the yeast Sac1p. Our results indicate that a variety of novel genes are expressed specifically during mating differentiation to mediate proper cell morphogenesis, cell fusion, and other steps of the mating process.

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Cell fusion and nuclear morphology defects in fig1Δ  and fig2Δ zygotes incubated at 16°C. Left panels are zygotes as  viewed by DIC. Center panels show the same zygotes stained  with the lipophilic dye FM4-64; the dye stains lipids and membrane, but not cell wall material. Panels at right show DAPI  staining of nucleic acids within zygotes. fig1Δ zygotes often display complete (top and bottom rows) or partial (middle row) fusion defects. fig2Δ zygotes have narrow conjugation bridges, and  often have cell fusion defects (top two rows) or nuclear migration/segregation defects (bottom two rows).
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Figure 7: Cell fusion and nuclear morphology defects in fig1Δ and fig2Δ zygotes incubated at 16°C. Left panels are zygotes as viewed by DIC. Center panels show the same zygotes stained with the lipophilic dye FM4-64; the dye stains lipids and membrane, but not cell wall material. Panels at right show DAPI staining of nucleic acids within zygotes. fig1Δ zygotes often display complete (top and bottom rows) or partial (middle row) fusion defects. fig2Δ zygotes have narrow conjugation bridges, and often have cell fusion defects (top two rows) or nuclear migration/segregation defects (bottom two rows).

Mentions: To help understand the functions of FIG1 and FIG2 in the differentiation of wild-type mating cells, we examined the cell morphologies and nuclear positions of prezygotes and zygotes formed by wild-type, fig1Δ, and fig2Δ strains mated at 16°C; this condition enhances the mating defects of the mutant strains. As observed for fig1Δ strains at 30°C, fig1Δ and fig2Δ zygotes formed at 16°C display cell fusion defects. These defects were quantified by examining prezygotes and zygotes using DIC microscopy, DAPI staining (to examine nuclear fusion and morphology), and staining with the lipophilic dye FM4-64 which decorates lipids and membranes, but not cell wall material (Fig. 7). As shown in Table VI, the incidence of partial and complete failures in cell fusion is increased markedly in fig1Δ zygotes (ninefold), and more modestly in fig2Δ zygotes (approximately twofold).


Pheromone-regulated genes required for yeast mating differentiation.

Erdman S, Lin L, Malczynski M, Snyder M - J. Cell Biol. (1998)

Cell fusion and nuclear morphology defects in fig1Δ  and fig2Δ zygotes incubated at 16°C. Left panels are zygotes as  viewed by DIC. Center panels show the same zygotes stained  with the lipophilic dye FM4-64; the dye stains lipids and membrane, but not cell wall material. Panels at right show DAPI  staining of nucleic acids within zygotes. fig1Δ zygotes often display complete (top and bottom rows) or partial (middle row) fusion defects. fig2Δ zygotes have narrow conjugation bridges, and  often have cell fusion defects (top two rows) or nuclear migration/segregation defects (bottom two rows).
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2140177&req=5

Figure 7: Cell fusion and nuclear morphology defects in fig1Δ and fig2Δ zygotes incubated at 16°C. Left panels are zygotes as viewed by DIC. Center panels show the same zygotes stained with the lipophilic dye FM4-64; the dye stains lipids and membrane, but not cell wall material. Panels at right show DAPI staining of nucleic acids within zygotes. fig1Δ zygotes often display complete (top and bottom rows) or partial (middle row) fusion defects. fig2Δ zygotes have narrow conjugation bridges, and often have cell fusion defects (top two rows) or nuclear migration/segregation defects (bottom two rows).
Mentions: To help understand the functions of FIG1 and FIG2 in the differentiation of wild-type mating cells, we examined the cell morphologies and nuclear positions of prezygotes and zygotes formed by wild-type, fig1Δ, and fig2Δ strains mated at 16°C; this condition enhances the mating defects of the mutant strains. As observed for fig1Δ strains at 30°C, fig1Δ and fig2Δ zygotes formed at 16°C display cell fusion defects. These defects were quantified by examining prezygotes and zygotes using DIC microscopy, DAPI staining (to examine nuclear fusion and morphology), and staining with the lipophilic dye FM4-64 which decorates lipids and membranes, but not cell wall material (Fig. 7). As shown in Table VI, the incidence of partial and complete failures in cell fusion is increased markedly in fig1Δ zygotes (ninefold), and more modestly in fig2Δ zygotes (approximately twofold).

Bottom Line: Transposon insertion alleles corresponding to 20 genes that are novel or had not previously been known to be pheromone regulated were examined for effects on the mating process.Mutations in four novel genes, FIG1, FIG2, KAR5/ FIG3, and FIG4 were found to cause mating defects.Our results indicate that a variety of novel genes are expressed specifically during mating differentiation to mediate proper cell morphogenesis, cell fusion, and other steps of the mating process.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Yale University, New Haven, Connecticut 06520-8103, USA.

ABSTRACT
Yeast cells mate by an inducible pathway that involves agglutination, mating projection formation, cell fusion, and nuclear fusion. To obtain insight into the mating differentiation of Saccharomyces cerevisiae, we carried out a large-scale transposon tagging screen to identify genes whose expression is regulated by mating pheromone. 91,200 transformants containing random lacZ insertions were screened for beta-galactosidase (beta-gal) expression in the presence and absence of alpha factor, and 189 strains containing pheromone-regulated lacZ insertions were identified. Transposon insertion alleles corresponding to 20 genes that are novel or had not previously been known to be pheromone regulated were examined for effects on the mating process. Mutations in four novel genes, FIG1, FIG2, KAR5/ FIG3, and FIG4 were found to cause mating defects. Three of the proteins encoded by these genes, Fig1p, Fig2p, and Fig4p, are dispensible for cell polarization in uniform concentrations of mating pheromone, but are required for normal cell polarization in mating mixtures, conditions that involve cell-cell communication. Fig1p and Fig2p are also important for cell fusion and conjugation bridge shape, respectively. The fourth protein, Kar5p/Fig3p, is required for nuclear fusion. Fig1p and Fig2p are likely to act at the cell surface as Fig1:: beta-gal and Fig2::beta-gal fusion proteins localize to the periphery of mating cells. Fig4p is a member of a family of eukaryotic proteins that contain a domain homologous to the yeast Sac1p. Our results indicate that a variety of novel genes are expressed specifically during mating differentiation to mediate proper cell morphogenesis, cell fusion, and other steps of the mating process.

Show MeSH
Related in: MedlinePlus