title: Ultrastructure of rapidly frozen and freeze-substituted germ tubes of an arbuscular mycorrhizal fungus and localization of polyphosphate.
abstract: In arbuscular mycorrhizas (AM), the supply of phosphorus from the fungi is one of the most important benefits to the host plant. Here we describe for the first time the ultrastructure and polyphosphate (poly P) distribution in rapidly frozen and freeze-substituted germ tubes of the AM fungus Gigaspora margarita. At the ultrastructural level, phosphorus distribution was analysed using energy-filtering transmission electron microscopy, and poly P was detected using an enzyme-affinity method. Semithin sections and live cells were also stained with 4',6-diamidino-2-phenylindole, which is not specific but fluoresces yellow when viewed under UV irradiation by binding with poly P. The cryotechnique method showed that extensive elongate ellipsoid vacuoles containing a uniform electron-opaque material occupied most of the cell volume. Combining the results of multiple methods revealed that poly P was localized in a dispersed form in vacuoles and in the outer fungal cell wall. These results show the significant potential of AM fungi for phosphorus storage based on its localization in the extensive complement of vacuoles in thick hyphae. The mechanism of translocation of poly P in tubular vacuoles, and the role of poly P in the cell wall, need to be elucidated.
authors.affiliation: Department of Food Production Science, Faculty of Agriculture, Shinshu University, Minami-minowa, Nagano 399-4598, Japan.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Kuga
authors.affiliation: Department of Food Production Science, Faculty of Agriculture, Shinshu University, Minami-minowa, Nagano 399-4598, Japan.
authors.forename: Katsuharu
authors.initials: K
authors.lastname: Saito
authors.affiliation: Department of Food Production Science, Faculty of Agriculture, Shinshu University, Minami-minowa, Nagano 399-4598, Japan.
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Nayuki
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: R Larry
authors.initials: RL
authors.lastname: Peterson
authors.affiliation: Department of Environmental Chemistry, National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki 305-8604, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Saito
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D015925:Cryopreservation; D005456:Fluorescent Dyes; D005615:Freezing; D025301:Hyphae / Q000378:metabolism / Q000648:ultrastructure*; D007211:Indoles; D046032:Microscopy, Energy-Filtering Transmission Electron; D038821:Mycorrhizae / Q000378:metabolism / Q000648:ultrastructure*; D011122:Polyphosphates / Q000378:metabolism*; D013057:Spectrum Analysis
chemical_list: D001426:Bacterial Proteins; D005456:Fluorescent Dyes; D007211:Indoles; D011122:Polyphosphates; C007293:DAPI; D017766:Acid Anhydride Hydrolases; C513394:Ppx protein, Escherichia coli