title: ATP-dependent but proton gradient-independent polyphosphate-synthesizing activity in extraradical hyphae of an arbuscular mycorrhizal fungus.
abstract: Arbuscular mycorrhizal (AM) fungi benefit their host plants by supplying phosphate obtained from the soil. Polyphosphate is thought to act as the key intermediate in this process, but little is currently understood about how polyphosphate is synthesized or translocated within arbuscular mycorrhizas. Glomus sp. strain HR1 was grown with marigold in a mesh bag compartment system, and extraradical hyphae were harvested and fractionated by density gradient centrifugation. Using this approach, three distinct layers were obtained: layers 1 and 2 were composed of amorphous and membranous materials, together with mitochondria, lipid bodies, and electron-opaque bodies, and layer 3 was composed mainly of partially broken hyphae and fragmented cell walls. The polyphosphate kinase/luciferase system, a highly sensitive polyphosphate detection method, enabled the detection of polyphosphate-synthesizing activity in layer 2 in the presence of ATP. This activity was inhibited by vanadate but not by bafilomycin A(1) or a protonophore, suggesting that ATP may not energize the reaction through H(+)-ATPase but may act as a direct substrate in the reaction. This report represents the first demonstration that AM fungi possess polyphosphate-synthesizing activity that is localized in the organelle fraction and not in the cytosol or at the plasma membrane.
authors.affiliation: Hokkaido University, Sapporo, Hokkaido 060-8589, Japan.
authors.forename: Chiharu
authors.initials: C
authors.lastname: Tani
authors.forename: Ryo
authors.initials: R
authors.lastname: Ohtomo
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Osaki
authors.forename: Yukari
authors.initials: Y
authors.lastname: Kuga
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Ezawa
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D055137:Glomeromycota / Q000201:enzymology* / Q000648:ultrastructure; D025301:Hyphae / Q000201:enzymology* / Q000648:ultrastructure; D018942:Macrolides / Q000494:pharmacology; D038821:Mycorrhizae / Q000201:enzymology* / Q000648:ultrastructure; D011122:Polyphosphates / Q000378:metabolism*; D011522:Protons; D014638:Vanadates / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D018942:Macrolides; D011122:Polyphosphates; D011522:Protons; D014638:Vanadates; C040929:bafilomycin A1; D000255:Adenosine Triphosphate; D017766:Acid Anhydride Hydrolases; D000251:Adenosine Triphosphatases; C022563:endopolyphosphatase