title: Role of phosphatidylinositol 3-phosphate in formation of forespore membrane in Schizosaccharomyces pombe.
abstract: Phosphatidylinositol (PI) 3-kinase (encoded by the pik3(+) gene) in Schizosaccharomyces pombe has been identified as a homologue of VPS34p, a protein required for proper vesicular protein sorting. The clone defective in this protein carries enlarged vacuoles and exhibits sensitivity to high temperature or high ion concentration. The effect of disruption of pik3(+) on sporulation of Sz. pombe was examined. The diploid cells underwent G(1) arrest and meiosis. However, the spores formed by the deltapik3 cells were not viable. Electron-microscopic analysis revealed that the growth of the forespore membrane of deltapik3 cells was not correctly orientated, failing to engulf the nucleus or forming extremely small spores, as was confirmed by the use of Spo3p-GFP and GFP-Psy1p, which are markers of the forespore membrane. The coating materials found along the forespore membrane of the wild-type were greatly reduced in these cells. PI 3-P, the product of Pik3p, was detected on the forespore membrane, suggesting that PI 3-P-dependent vesicle transport may take place in formation of the forespore membrane. Misshaped forespore membrane, accumulation of vesicles, formation of small non-viable spores, and suppression by over expression of Psy1p were the phenotypes commonly seen in deltapik3 and deltaspo3 cells, suggesting a relationship between the functions of Pik3p and Spo3p in formation of the forespore membrane in Sz. pombe.
authors.affiliation: Laboratory of Biological Chemistry, Graduate School of Agriculture and Life Science, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Onishi
authors.forename: Takako
authors.initials: T
authors.lastname: Koga
authors.forename: Rika
authors.initials: R
authors.lastname: Morita
authors.forename: Yoko
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Taro
authors.initials: T
authors.lastname: Nakamura
authors.forename: Chikashi
authors.initials: C
authors.lastname: Shimoda
authors.forename: Kaoru
authors.initials: K
authors.lastname: Takegawa
authors.forename: Aiko
authors.initials: A
authors.lastname: Hirata
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Fukui
mesh_terms: D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D004271:DNA, Fungal / Q000235:genetics; D005434:Flow Cytometry; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal / Q000502:physiology; D008854:Microscopy, Electron; D009154:Mutation / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D010957:Plasmids; D012568:Schizosaccharomyces / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D013172:Spores, Fungal / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D004271:DNA, Fungal; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates; C055525:phosphatidylinositol 3-phosphate