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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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Hyperagglutination and small colony phenotypes observed in matings of fig2Δ and kar5Δ/fig3Δ strains. (A) Unilateral  and bilateral matings involving fig2Δ strains cause hyperagglutination, observable as rapid sedimentation of extensive cell clusters. Depicted are bilateral matings of wild-type and figΔ strains.  (B) Bilateral matings of MATa kar5Δ/fig3Δ and MATα kar5Δ/ fig3Δ cells often produce very small colonies. The left panels are  magnifications of sections of the plates shown on the right. Plates  were incubated for 36 h. The large colonies are visible after 1 d.  Both large and small colonies from the kar5Δ/fig3Δ matings contain abnormal cells as described in the text.
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Figure 4: Hyperagglutination and small colony phenotypes observed in matings of fig2Δ and kar5Δ/fig3Δ strains. (A) Unilateral and bilateral matings involving fig2Δ strains cause hyperagglutination, observable as rapid sedimentation of extensive cell clusters. Depicted are bilateral matings of wild-type and figΔ strains. (B) Bilateral matings of MATa kar5Δ/fig3Δ and MATα kar5Δ/ fig3Δ cells often produce very small colonies. The left panels are magnifications of sections of the plates shown on the right. Plates were incubated for 36 h. The large colonies are visible after 1 d. Both large and small colonies from the kar5Δ/fig3Δ matings contain abnormal cells as described in the text.

Mentions: After the discovery that figΔ mutants exhibit altered mating efficiencies, we sought to determine the phenotypic basis of these effects. Two macroscopic phenotypes were observed in matings involving fig2Δ and kar5/fig3Δ mutants. During mating, wild-type cells gather into clusters through agglutination. fig2Δ strains exhibit a hyperagglutination phenotype in which mating cells aggregate to a greater extent than wild-type cells. This phenotype is observed by both uni- and bilateral crosses using settling assays (Fig. 4 A), and microscopic examination of mating cells (data not shown). Hyperagglutination caused by the fig2Δ mutation is an interaction specific to mixtures of mating cells; fig2Δ mutant strains of either mating type do not aggregate during vegetative growth or when mixed with cells of the same mating type. Hyperagglutination of fig2Δ strains during mating was observed at both 30° and 16°C, indicating that the cold sensitivity of fig2Δ mutant matings is caused by a defect independent of agglutination.


Pheromone-regulated genes required for yeast mating differentiation.

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

Hyperagglutination and small colony phenotypes observed in matings of fig2Δ and kar5Δ/fig3Δ strains. (A) Unilateral  and bilateral matings involving fig2Δ strains cause hyperagglutination, observable as rapid sedimentation of extensive cell clusters. Depicted are bilateral matings of wild-type and figΔ strains.  (B) Bilateral matings of MATa kar5Δ/fig3Δ and MATα kar5Δ/ fig3Δ cells often produce very small colonies. The left panels are  magnifications of sections of the plates shown on the right. Plates  were incubated for 36 h. The large colonies are visible after 1 d.  Both large and small colonies from the kar5Δ/fig3Δ matings contain abnormal cells as described in the text.
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Related In: Results  -  Collection

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Figure 4: Hyperagglutination and small colony phenotypes observed in matings of fig2Δ and kar5Δ/fig3Δ strains. (A) Unilateral and bilateral matings involving fig2Δ strains cause hyperagglutination, observable as rapid sedimentation of extensive cell clusters. Depicted are bilateral matings of wild-type and figΔ strains. (B) Bilateral matings of MATa kar5Δ/fig3Δ and MATα kar5Δ/ fig3Δ cells often produce very small colonies. The left panels are magnifications of sections of the plates shown on the right. Plates were incubated for 36 h. The large colonies are visible after 1 d. Both large and small colonies from the kar5Δ/fig3Δ matings contain abnormal cells as described in the text.
Mentions: After the discovery that figΔ mutants exhibit altered mating efficiencies, we sought to determine the phenotypic basis of these effects. Two macroscopic phenotypes were observed in matings involving fig2Δ and kar5/fig3Δ mutants. During mating, wild-type cells gather into clusters through agglutination. fig2Δ strains exhibit a hyperagglutination phenotype in which mating cells aggregate to a greater extent than wild-type cells. This phenotype is observed by both uni- and bilateral crosses using settling assays (Fig. 4 A), and microscopic examination of mating cells (data not shown). Hyperagglutination caused by the fig2Δ mutation is an interaction specific to mixtures of mating cells; fig2Δ mutant strains of either mating type do not aggregate during vegetative growth or when mixed with cells of the same mating type. Hyperagglutination of fig2Δ strains during mating was observed at both 30° and 16°C, indicating that the cold sensitivity of fig2Δ mutant matings is caused by a defect independent of agglutination.

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