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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: Mutations in four novel genes, FIG1, FIG2, KAR5/ FIG3, and FIG4 were found to cause mating defects.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.

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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Actin distribution in wild-type, fig1Δ, fig2Δ and fig4Δ  polarized cells containing mating projections. Cells shown are derived from mating mixtures stained with rhodamine-conjugated  phalloidin after fixation. fig1Δ and fig4Δ cells typically contain  less actin at the growing tip of the mating projection, whereas actin distribution in fig2Δ appears similar to that of wild-type cells.
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Figure 6: Actin distribution in wild-type, fig1Δ, fig2Δ and fig4Δ polarized cells containing mating projections. Cells shown are derived from mating mixtures stained with rhodamine-conjugated phalloidin after fixation. fig1Δ and fig4Δ cells typically contain less actin at the growing tip of the mating projection, whereas actin distribution in fig2Δ appears similar to that of wild-type cells.

Mentions: fig1Δ, and to a lesser extent fig4Δ, mating mixtures have fewer medium and large polarized cells than wild-type or fig3Δ matings (Fig. 5; Table V). Many of the fig1Δ and fig4Δ cells that are polarized possess mating projections with tips that are broader and less focused than those of wild-type cells; for these strains the percentage of large cells with pointed projections was less than half that of wild-type cells or other figΔ mutants (Fig. 5, insets; Table V). In addition, in the case of fig4Δ cells, we often observe multiple bumps around the cell periphery of unpolarized but enlarged cells, suggestive of failures in the intial establishment of mating cell polarity. We also examined the distribution of actin in these strains by rhodamine conjugated–phalloidin staining (Fig. 6). The pattern of actin staining at the mating projection tip is typically less intense and more dispersed in both fig1Δ and fig4Δ cells compared to that of wild-type cells, whereas actin polarization remains normal in fig2Δ cells. Thus, whereas FIG1 and FIG4 are dispensible for forming normal projections in isotropic levels of mating pheromone, in mating mixtures these genes are important both for the execution of cell polarization and the development of mating projection shape (see Discussion). Although the effects of the fig 1Δ and fig4Δ mutations on cell polarization are similar, differences in zygote morphologies between these two mutants suggest they perform different functions in the mating process; fig 1Δ, but not fig4Δ, zygotes display cell fusion defects (Fig. 5, and see below).


Pheromone-regulated genes required for yeast mating differentiation.

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

Actin distribution in wild-type, fig1Δ, fig2Δ and fig4Δ  polarized cells containing mating projections. Cells shown are derived from mating mixtures stained with rhodamine-conjugated  phalloidin after fixation. fig1Δ and fig4Δ cells typically contain  less actin at the growing tip of the mating projection, whereas actin distribution in fig2Δ appears similar to that of wild-type cells.
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Related In: Results  -  Collection

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

Figure 6: Actin distribution in wild-type, fig1Δ, fig2Δ and fig4Δ polarized cells containing mating projections. Cells shown are derived from mating mixtures stained with rhodamine-conjugated phalloidin after fixation. fig1Δ and fig4Δ cells typically contain less actin at the growing tip of the mating projection, whereas actin distribution in fig2Δ appears similar to that of wild-type cells.
Mentions: fig1Δ, and to a lesser extent fig4Δ, mating mixtures have fewer medium and large polarized cells than wild-type or fig3Δ matings (Fig. 5; Table V). Many of the fig1Δ and fig4Δ cells that are polarized possess mating projections with tips that are broader and less focused than those of wild-type cells; for these strains the percentage of large cells with pointed projections was less than half that of wild-type cells or other figΔ mutants (Fig. 5, insets; Table V). In addition, in the case of fig4Δ cells, we often observe multiple bumps around the cell periphery of unpolarized but enlarged cells, suggestive of failures in the intial establishment of mating cell polarity. We also examined the distribution of actin in these strains by rhodamine conjugated–phalloidin staining (Fig. 6). The pattern of actin staining at the mating projection tip is typically less intense and more dispersed in both fig1Δ and fig4Δ cells compared to that of wild-type cells, whereas actin polarization remains normal in fig2Δ cells. Thus, whereas FIG1 and FIG4 are dispensible for forming normal projections in isotropic levels of mating pheromone, in mating mixtures these genes are important both for the execution of cell polarization and the development of mating projection shape (see Discussion). Although the effects of the fig 1Δ and fig4Δ mutations on cell polarization are similar, differences in zygote morphologies between these two mutants suggest they perform different functions in the mating process; fig 1Δ, but not fig4Δ, zygotes display cell fusion defects (Fig. 5, and see below).

Bottom Line: Mutations in four novel genes, FIG1, FIG2, KAR5/ FIG3, and FIG4 were found to cause mating defects.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.

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