Ultrastructure of rapidly frozen and freeze-substituted germ tubes of an arbuscular mycorrhizal fungus and localization of polyphosphate

Yukari Kuga, Katsuharu Saito, Keiichiro Nayuki, R. Larry Peterson, Masanori Saito

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


• 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.

Original languageEnglish
Pages (from-to)189-200
Number of pages12
JournalNew Phytologist
Issue number1
Publication statusPublished - 2008 Apr
Externally publishedYes


  • Arbuscular mycorrhizal (AM) fungus
  • Cryo-TEM
  • Energy-filtering transmission electron microscopy (EF-TEM)
  • Enzyme-affinity immuno-gold labelling
  • Gigaspora margarita
  • Polyphosphate (poly P)
  • Tubular vacuole

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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