Rapid accumulation of polyphosphate in extraradical hyphae of an arbuscular mycorrhizal fungus as revealed by histochemistry and a polyphosphate kinase/luciferase system

Authors

  • Tatsuhiro Ezawa,

    Corresponding author
    1. Graduate School of Bioagricultural Science, Nagoya University, Togo-cho, Aichi 470–0151 Japan;
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  • Timothy R. Cavagnaro,

    1. Soil and Land Systems, School of Earth and Environmental Sciences, The University of Adelaide, SA 5005 Australia;
    2. Present address: Department of Land, Air & Water Resources, University of California, Davis, One Shields Avenue, Davis, CA 95616–8627, USA
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  • Sally E. Smith,

    1. Soil and Land Systems, School of Earth and Environmental Sciences, The University of Adelaide, SA 5005 Australia;
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  • F. Andrew Smith,

    1. Soil and Land Systems, School of Earth and Environmental Sciences, The University of Adelaide, SA 5005 Australia;
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  • Ryo Ohtomo

    1. National Institute of Livestock and Grassland Science, Nishi-nasuno, Tochigi 329–2793 Japan;
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Author for correspondence: Tatsuhiro Ezawa Tel: +81 561 37 0207 Fax: +81 561 38 4473 Email: tatsu@agr.nagoya-u.ac.jp

Summary

The rate of polyphosphate accumulation in extraradical hyphae of an arbuscular mycorrhizal fungus was investigated by conventional histochemistry and a new enzymatic method using a bacterial enzyme, polyphosphate kinase. Marigold (Tagetes patula cv. Bonanza Orange) was inoculated with Archaeospora leptoticha and grown under P-deficient conditions. Extraradical hyphae were harvested at 0, 1, 3 and 24 h after 1 mm P-application. PolyP levels were assessed by both metachromasy of Toluidine blue O and polyphosphate kinase which converted polyP to ATP followed by the ATP-luciferase assay. Percentage of hyphae with metachromatic granules was increased from 25 to 44% from 0 to 1 h, and a maximum of 50% was reach by 3 h. Polyphosphate content was doubled from 1 to 3 h after P-application (4.8–10.0 mol as Pi mg−1 protein) at a rate of 46.4 ± 15.1 nmol min−1 mg−1. The rate of polyphosphate accumulation in the hyphae was surprisingly rapid as those of polyphosphate-hyper accumulating microorganisms. The enzymatic method employed in the present study allows highly specific and sensitive assessment of polyphosphate in the mycorrhizal system.

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