Myristate can be used as a carbon and energy source for the asymbiotic growth of arbuscular mycorrhizal fungi

Yuta Sugiura, Rei Akiyama, Sachiko Tanaka, Koji Yano, Hiromu Kameoka, Shiori Marui, Masanori Saito, Masayoshi Kawaguchi, Kohki Akiyama, Katsuharu Saito

Research output: Contribution to journalArticlepeer-review

Abstract

Arbuscular mycorrhizal (AM) fungi, forming symbiotic associations with land plants, are obligate symbionts that cannot complete their natural life cycle without a host. The fatty acid auxotrophy of AM fungi is supported by recent studies showing that lipids synthesized by the host plants are transferred to the fungi, and that the latter lack genes encoding cytosolic fatty acid synthases.Therefore, to establish an asymbiotic cultivation system for AM fungi, we tried to identify the fatty acids that could promote biomass production. To determine whether AM fungi can grow on medium supplied with fatty acids or lipids under asymbiotic conditions, we tested eight saturated or unsaturated fatty acids (C12 to C18) and two β-monoacylglycerols. Only myristate (C14:0) led to an increase in the biomass of Rhizophagus irregularis, inducing extensive hyphal growth and formation of infectioncompetent secondary spores. However, such spores were smaller than those generated symbiotically. Furthermore, we demonstrated that R. irregularis can take up fatty acids in its branched hyphae and use myristate as a carbon and energy source. Myristate also promoted the growth of Rhizophagus clarus and Gigaspora margarita. Finally, mixtures of myristate and palmitate accelerated fungal growth and induced a substantial change in fatty acid composition of triacylglycerol compared with single myristate application, although palmitate was not used as a carbon source for cell wall biosynthesis in this culture system. Our findings demonstrate that myristate boosts the asymbiotic growth of AM fungi and can also serve as a carbon and energy source.

Original languageEnglish
Pages (from-to)25779-25788
Number of pages10
JournalProceedings of the National Academy of Sciences of the United States of America
Volume117
Issue number41
DOIs
Publication statusPublished - 2020 Oct 13
Externally publishedYes

Keywords

  • Fatty acid auxotrophy
  • Immobilized cell culture
  • Mycorrhizal symbiosis
  • Pure culture

ASJC Scopus subject areas

  • General

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