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Applied and Environmental Microbiology, November 2009, p. 7044-7050, Vol. 75, No. 22
0099-2240/09/$08.00+0     doi:10.1128/AEM.01519-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

ATP-Dependent but Proton Gradient-Independent Polyphosphate-Synthesizing Activity in Extraradical Hyphae of an Arbuscular Mycorrhizal Fungus{triangledown} ,{dagger}

Chiharu Tani,1 Ryo Ohtomo,2 Mitsuru Osaki,1 Yukari Kuga,3 and Tatsuhiro Ezawa1*

Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan,1 NARO-NILGS, Nasushiobara, Tochigi 329-2793, Japan,2 Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi Hiroshima, Hiroshima 739-8521, Japan3

Received 29 June 2009/ Accepted 10 September 2009

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 A1 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.

* Corresponding author. Mailing address: Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan. Phone and fax: 81-11-857-9732. E-mail: tatsu{at}res.agr.hokudai.ac.jp

{triangledown} Published ahead of print on 18 September 2009.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

Applied and Environmental Microbiology, November 2009, p. 7044-7050, Vol. 75, No. 22
0099-2240/09/$08.00+0     doi:10.1128/AEM.01519-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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