title: Polyphosphate accumulation is driven by transcriptome alterations that lead to near-synchronous and near-equivalent uptake of inorganic cations in an arbuscular mycorrhizal fungus.
abstract: Arbuscular mycorrhizal (AM) fungi accumulate a massive amount of phosphate as polyphosphate to deliver to the host, but the underlying physiological and molecular mechanisms have yet to be elucidated. In the present study, the dynamics of cationic components during polyphosphate accumulation were investigated in conjunction with transcriptome analysis. Rhizophagus sp. HR1 was grown with Lotus japonicus under phosphorus-deficient conditions, and extraradical mycelia were harvested after phosphate application at prescribed intervals. Levels of polyphosphate, inorganic cations and amino acids were measured, and RNA-Seq was performed on the Illumina platform. Phosphate application triggered not only polyphosphate accumulation but also near-synchronous and near-equivalent uptake of Na(+) , K(+) , Ca(2+) and Mg(2+) , whereas no distinct changes in the levels of amino acids were observed. During polyphosphate accumulation, the genes responsible for mineral uptake, phosphate and nitrogen metabolism and the maintenance of cellular homeostasis were up-regulated. The results suggest that inorganic cations play a major role in neutralizing the negative charge of polyphosphate, and these processes are achieved by the orchestrated regulation of gene expression. Our findings provide, for the first time, a global picture of the cellular response to increased phosphate availability, which is the initial process of nutrient delivery in the associations.
authors.affiliation: Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kikuchi
authors.affiliation: Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.
authors.forename: Nowaki
authors.initials: N
authors.lastname: Hijikata
authors.affiliation: Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.
authors.forename: Kaede
authors.initials: K
authors.lastname: Yokoyama
authors.affiliation: National Agriculture and Food Research Organization, Hokkaido Agricultural Research Center, Sapporo, 062-8555, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Ohtomo
authors.affiliation: Division of Symbiotic Systems, National Institute for Basic Biology, Okazaki, 444-8585, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Handa
authors.affiliation: Division of Symbiotic Systems, National Institute for Basic Biology, Okazaki, 444-8585, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Kawaguchi
authors.affiliation: Faculty of Agriculture, Shinshu University, Minamiminowa, 399-4598, Japan.
authors.forename: Katsuharu
authors.initials: K
authors.lastname: Saito
authors.affiliation: Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Ezawa
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D001692:Biological Transport; D002412:Cations / Q000378:metabolism; D005658:Fungi / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D000070116:Lotus / Q000382:microbiology*; D038821:Mycorrhizae / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D011122:Polyphosphates / Q000378:metabolism*; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome
chemical_list: D000596:Amino Acids; D002412:Cations; D011122:Polyphosphates; D012331:RNA, Fungal; D009584:Nitrogen
keywords: arbuscular mycorrhizal (AM) fungi; inorganic cation; polyphosphate; symbiosis; transcriptome