| Title: | Cell fusion during yeast mating requires high levels of a-factor mating pheromone |
| Author(s): | Brizzio V; Gammie AE; Nijbroek G; Michaelis S; Rose MD; |
| Address: | "Department of Molecular Biology, Princeton University, New Jersey 08544-1014, USA" |
| ISSN/ISBN: | 0021-9525 (Print) 1540-8140 (Electronic) 0021-9525 (Linking) |
| Abstract: | "During conjugation, two yeast cells fuse to form a single zygote. Cell fusion requires extensive remodeling of the cell wall, both to form a seal between the two cells and to remove the intervening material. The two plasma membranes then fuse to produce a continuous cytoplasm. We report the characterization of two cell fusion defective (Fus-) mutants, fus5 and fus8, isolated previously in our laboratory. Fluorescence and electron microscopy demonstrated that the fus5 and fus8 mutant zygotes were defective for cell wall remodeling/removal but not plasma membrane fusion. Strikingly, fus5 and fus8 were a specific; both mutations caused the mutant phenotype when present in the MATa parent but not in the MAT alpha parent. Consistent with an a-specific defect, the fus5 and fus8 mutants produced less a-factor than the isogenic wild-type strain. FUS5 and FUS8 were determined to be allelic to AXL1 and RAM1, respectively, two genes known to be required for biogenesis of a-factor. Several experiments demonstrated that the partial defect in a-factor production resulted in the Fus- phenotype. First, overexpression of a-factor in the fus mutants suppressed the Fus- defect. Second, matings to an MAT alpha partner supersensitive to mating pheromone (sst2 delta) suppressed the Fus- defect in trans. Finally, the gene encoding a-factor, MFA1, was placed under the control of a repressible promoter; reduced levels of wild-type a-factor caused an identical cell fusion defect during mating. We conclude that high levels of pheromone are required as one component of the signal for prezygotes to initiate cell fusion" |
| Keywords: | "Alleles Escherichia coli/genetics Fungal Proteins/genetics/metabolism Gene Expression Regulation, Fungal/physiology Insulysin/genetics Lipoproteins/*genetics/*metabolism Metalloendopeptidases Microscopy, Electron Molecular Sequence Data Mutation/physiolog;" |
| Notes: | "MedlineBrizzio, V Gammie, A E Nijbroek, G Michaelis, S Rose, M D eng R01 GM037739/GM/NIGMS NIH HHS/ GM37739/GM/NIGMS NIH HHS/ GM41223/GM/NIGMS NIH HHS/ Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. 1996/12/01 J Cell Biol. 1996 Dec; 135(6 Pt 2):1727-39. doi: 10.1083/jcb.135.6.1727" |
