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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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Electron micrographs of thin sections through  zygotes formed from bilateral  matings. (A) wild-type; (B)  fig1Δ mutant, complete fusion defect; (C) fig1Δ mutant, partial fusion defect;  and (D) fig2Δ mutant, note  narrow fusion bridge. n indicates the nucleus.
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Figure 8: Electron micrographs of thin sections through zygotes formed from bilateral matings. (A) wild-type; (B) fig1Δ mutant, complete fusion defect; (C) fig1Δ mutant, partial fusion defect; and (D) fig2Δ mutant, note narrow fusion bridge. n indicates the nucleus.

Mentions: To further examine the cell and nuclear fusion defects visualized by light microscopy, we performed electron microscopic analysis on thin section preparations of wild-type, fig1Δ, and fig2Δ zygotes (Fig. 8). Inspection of micrographs of the fig1Δ zygotes confirms the presence of undissolved cell wall materials and membrane causing both partial and complete fusion defects (Fig. 8, B and C; this is particularly evident in higher magnification micrographs; data not shown). Moreover, examination of the partial fusion defects by both fluorescent microscopic techniques and electron microscopy indicates that nuclear fusion is a robust process, capable of being executed through very small regions of cytoplasmic continuity (for example, Fig. 7, fig1Δ center panel; Fig. 8 C; and Table VI, partial fusion defect column). Analysis of fig2Δ zygotes revealed elongated nuclear morphologies consistent with those visualized by DAPI staining of whole zygotes. In summary, these different data demonstrate that fig1Δ and fig2Δ zygotes exhibit both cell fusion and nuclear morphology defects.


Pheromone-regulated genes required for yeast mating differentiation.

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

Electron micrographs of thin sections through  zygotes formed from bilateral  matings. (A) wild-type; (B)  fig1Δ mutant, complete fusion defect; (C) fig1Δ mutant, partial fusion defect;  and (D) fig2Δ mutant, note  narrow fusion bridge. n indicates the nucleus.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2140177&req=5

Figure 8: Electron micrographs of thin sections through zygotes formed from bilateral matings. (A) wild-type; (B) fig1Δ mutant, complete fusion defect; (C) fig1Δ mutant, partial fusion defect; and (D) fig2Δ mutant, note narrow fusion bridge. n indicates the nucleus.
Mentions: To further examine the cell and nuclear fusion defects visualized by light microscopy, we performed electron microscopic analysis on thin section preparations of wild-type, fig1Δ, and fig2Δ zygotes (Fig. 8). Inspection of micrographs of the fig1Δ zygotes confirms the presence of undissolved cell wall materials and membrane causing both partial and complete fusion defects (Fig. 8, B and C; this is particularly evident in higher magnification micrographs; data not shown). Moreover, examination of the partial fusion defects by both fluorescent microscopic techniques and electron microscopy indicates that nuclear fusion is a robust process, capable of being executed through very small regions of cytoplasmic continuity (for example, Fig. 7, fig1Δ center panel; Fig. 8 C; and Table VI, partial fusion defect column). Analysis of fig2Δ zygotes revealed elongated nuclear morphologies consistent with those visualized by DAPI staining of whole zygotes. In summary, these different data demonstrate that fig1Δ and fig2Δ zygotes exhibit both cell fusion and nuclear morphology defects.

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