title: Distinct morphological phenotypes of cell fusion mutants.
abstract: Cell fusion in yeast is the process by which two haploid cells fuse to form a diploid zygote. To dissect the pathway of cell fusion, we phenotypically and genetically characterized four cell fusion mutants, fus6/spa2, fus7/rvs161, fus1, and fus2. First, we examined the complete array of single and double mutants. In all cases but one, double mutants exhibited stronger cell fusion defects than single mutants. The exception was rvs161Delta fus2Delta, suggesting that Rvs161p and Fus2p act in concert. Dosage suppression analysis showed that Fus1p and Fus2p act downstream or parallel to Rvs161p and Spa2p. Second, electron microscopic analysis was used to define the mutant defects in cell fusion. In wild-type prezygotes vesicles were aligned and clustered across the cell fusion zone. The vesicles were associated with regions of cell wall thinning. Analysis of Fus- zygotes indicated that Fus1p was required for the normal localization of the vesicles to the zone of cell fusion, and Spa2p facilitated their clustering. In contrast, Fus2p and Rvs161p appeared to act after vesicle positioning. These findings lead us to propose that cell fusion is mediated in part by the localized release of vesicles containing components essential for cell fusion.
authors.affiliation: Princeton University, Princeton, New Jersey 08544-1014, USA.
authors.forename: A E
authors.initials: AE
authors.lastname: Gammie
authors.forename: V
authors.initials: V
authors.lastname: Brizzio
authors.forename: M D
authors.initials: MD
authors.lastname: Rose
mesh_terms: D000075686:COP9 Signalosome Complex; D002462:Cell Membrane; D002473:Cell Wall; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000502:physiology*; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D019204:GTP-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D016296:Mutagenesis; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology; D011506:Proteins; D012097:Repressor Proteins; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D003598:Cytoskeletal Proteins; C490024:FUS1 protein, S cerevisiae; C095898:FUS2 protein, S cerevisiae; D005656:Fungal Proteins; C103315:GPS1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010940:Plant Proteins; D011506:Proteins; C089181:RVS161 protein, S cerevisiae; D012097:Repressor Proteins; C065889:SPA2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000075686:COP9 Signalosome Complex; D019204:GTP-Binding Proteins