title: Lipid droplets of arbuscular mycorrhizal fungi emerge in concert with arbuscule collapse.
abstract: Plants share photosynthetically fixed carbon with arbuscular mycorrhizal (AM) fungi to maintain their growth and nutrition. AM fungi are oleogenic fungi that contain numerous lipid droplets in their syncytial mycelia during most of their life cycle. These lipid droplets are probably used for supporting growth of extraradical mycelia and propagation; however, when and where the lipid droplets are produced remains unclear. To address these issues, we investigated the correlation between intracellular colonization stages and the appearance of fungal lipid droplets in roots by a combination of vital staining of fungal structures, selective staining of lipids and live imaging. We discovered that a surge of lipid droplets coincided with the collapse of arbuscular branches, indicating that arbuscule collapse and the emergence of lipid droplets may be associated processes. This phenomenon was observed in the model AM fungus Rhizophagus irregularis and the ancestral member of AM fungi Paraglomus occultum. Because the collapsing arbuscules were metabolically inactive, the emerged lipid droplets are probably derived from preformed lipids but not de novo synthesized. Our observations highlight a novel mode of lipid release by AM fungi.
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, 113-8657 Japan akobae@mail.ecc.u-tokyo.ac.jp.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kobae
authors.affiliation: Institute of Genetics, Faculty of Biology, University of Munich (LMU), 82152 Martinsried, Germany.
authors.forename: Caroline
authors.initials: C
authors.lastname: Gutjahr
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
authors.forename: Uta
authors.initials: U
authors.lastname: Paszkowski
authors.affiliation: National Agriculture and Food Research Organization (NARO) Institute of Livestock and Grassland Science, 768 Senbonmatsu, Nasushiobara, Tochigi, 329-2793 Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kojima
authors.affiliation: Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, 113-8657 Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Fujiwara
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan Ryukoku University, 67 Tsukamoto-cho, Fukakusa, Fushimi-ku, Kyoto, 612-8577 Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Hata
mesh_terms: D055137:Glomeromycota / Q000502:physiology*; D066292:Lipid Droplets / Q000502:physiology*; D038821:Mycorrhizae / Q000502:physiology*; D018517:Plant Roots / Q000382:microbiology; D013559:Symbiosis
keywords: Arbuscular collapse; Arbuscular mycorrhiza; Lipid droplets; Live imaging; Paraglomus occultum; Phosphate transporter