Abstract
Spore formation in yeast is an unusual form of cell division in which the daughter cells are formed within the mother cell cytoplasm. This division requires the de novo synthesis of a membrane compartment, termed the prospore membrane, which engulfs the daughter nuclei. The effect of mutations in late-acting genes on sporulation was investigated. Mutation of SEC1, SEC4, or SEC8 blocked spore formation, and electron microscopic analysis of the sec4-8 mutant indicated that this inability to produce spores was caused by a failure to form the prospore membrane. The soluble NSF attachment protein 25 (SNAP-25) homologue SEC9, by contrast, was not required for sporulation. The absence of a requirement for SEC9 was shown to be due to the sporulation-specific induction of a second, previously undescribed, SNAP-25 homologue, termed SPO20. These results define a developmentally regulated branch of the secretory pathway and suggest that spore morphogenesis in yeast proceeds by the targeting and fusion of secretory vesicles to form new plasma membranes in the interior of the mother cell. Consistent with this model, the extracellular proteins Gas1p and Cts1p were localized to an internal compartment in sporulating cells. Spore formation in yeast may be a useful model for understanding secretion-driven cell division events in a variety of plant and animal systems.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Carboxypeptidases / metabolism
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Carrier Proteins*
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Cathepsin A
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Cell Division
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Cell Membrane / physiology
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Cell Membrane / ultrastructure
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Fungal Proteins / genetics
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Fungal Proteins / metabolism
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GTP-Binding Proteins / genetics
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GTP-Binding Proteins / metabolism
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Genes, Fungal
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Genotype
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Glycoside Hydrolases / metabolism
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Membrane Proteins*
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Munc18 Proteins
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Mutagenesis
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / metabolism
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Polymerase Chain Reaction
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Proteins / genetics
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Proteins / metabolism
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Qc-SNARE Proteins
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Saccharomyces cerevisiae / cytology
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / physiology*
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Saccharomyces cerevisiae Proteins*
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Spores, Fungal / physiology
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Spores, Fungal / ultrastructure
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Vacuoles / physiology
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Vacuoles / ultrastructure
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Vesicular Transport Proteins*
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beta-Fructofuranosidase
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rab GTP-Binding Proteins*
Substances
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Carrier Proteins
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Fungal Proteins
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Membrane Proteins
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Munc18 Proteins
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Nerve Tissue Proteins
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Proteins
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Qc-SNARE Proteins
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SEC1 protein, S cerevisiae
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SEC8 protein, S cerevisiae
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SEC9 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Vesicular Transport Proteins
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Glycoside Hydrolases
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beta-Fructofuranosidase
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Carboxypeptidases
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Cathepsin A
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GTP-Binding Proteins
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SEC4 protein, S cerevisiae
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rab GTP-Binding Proteins