Stimulation of asymbiotic sporulation in arbuscular mycorrhizal fungi by fatty acids

Hiromu Kameoka, Ippo Tsutsui, Katsuharu Saito, Yusuke Kikuchi, Yoshihiro Handa, Tatsuhiro Ezawa, Hideo Hayashi, Masayoshi Kawaguchi, Kohki Akiyama

Research output: Contribution to journalLetterpeer-review

27 Citations (Scopus)


Arbuscular mycorrhizal (AM) fungi are obligate symbionts that depend on living host plants to complete their life cycle1,2. This feature, which leads to their unculturability in the absence of plants, strongly hinders basic research and agricultural application of AM fungi. However, at least one AM fungus can grow and develop fertile spores independently of a host plant in co-culture with the bacterium Paenibacillus validus3. The bacteria-derived substances are thought to act as stimulants or nutrients for fungal sporulation, but these molecules have not been identified. Here, we show that (S)-12-methyltetradecanoic acid4,5, a methyl branched-chain fatty acid isolated from bacterial cultures, stimulates the branching of hyphae germinated from mother spores and the formation of secondary spores in axenic culture of the AM fungus Rhizophagus irregularis. Extensive testing of fatty acids revealed that palmitoleic acid induces more secondary spores than the bacterial fatty acid in R. irregularis. These induced spores have the ability to infect host plant roots and to generate daughter spores. Our work shows that, in addition to a major source of organic carbon6–9, fatty acids act as stimulants to induce infection-competent secondary spores in the asymbiotic stage and could provide the key to developing the axenic production of AM inoculum.

Original languageEnglish
Pages (from-to)1654-1660
Number of pages7
JournalNature Microbiology
Issue number10
Publication statusPublished - 2019 Oct 1
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Applied Microbiology and Biotechnology
  • Genetics
  • Microbiology (medical)
  • Cell Biology


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