title: Aquaporin-mediated long-distance polyphosphate translocation directed towards the host in arbuscular mycorrhizal symbiosis: application of virus-induced gene silencing.
abstract: Arbuscular mycorrhizal fungi translocate polyphosphate through hyphae over a long distance to deliver to the host. More than three decades ago, suppression of host transpiration was found to decelerate phosphate delivery of the fungal symbiont, leading us to hypothesize that transpiration provides a primary driving force for polyphosphate translocation, probably via creating hyphal water flow in which fungal aquaporin(s) may be involved. The impact of transpiration suppression on polyphosphate translocation through hyphae of Rhizophagus clarus was evaluated. An aquaporin gene expressed in intraradical mycelia was characterized and knocked down by virus-induced gene silencing to investigate the involvement of the gene in polyphosphate translocation. Rhizophagus clarus aquaporin 3 (RcAQP3) that was most highly expressed in intraradical mycelia encodes an aquaglyceroporin responsible for water transport across the plasma membrane. Knockdown of RcAQP3 as well as the suppression of host transpiration decelerated polyphosphate translocation in proportion to the levels of knockdown and suppression, respectively. These results provide the first insight into the mechanism underlying long-distance polyphosphate translocation in mycorrhizal associations at the molecular level, in which host transpiration and the fungal aquaporin play key roles. A hypothetical model of the translocation is proposed for further elucidation of the mechanism.
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: 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: Chikara
authors.initials: C
authors.lastname: Masuta
authors.affiliation: Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan.
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Ezawa
mesh_terms: D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D005800:Genes, Fungal; D055137:Glomeromycota / Q000235:genetics / Q000502:physiology; D000070116:Lotus / Q000382:microbiology*; D008954:Models, Biological; D025282:Mycelium / Q000378:metabolism; D038821:Mycorrhizae / Q000502:physiology*; D010802:Phylogeny; D018526:Plant Transpiration / Q000502:physiology; D010942:Plant Viruses / Q000378:metabolism*; D011122:Polyphosphates / Q000378:metabolism*; D013559:Symbiosis; D014026:Nicotiana / Q000382:microbiology*
chemical_list: D020346:Aquaporins; D011122:Polyphosphates
keywords: Rhizophagus clarus; aquaglyceroporin; aquaporin; arbuscular mycorrhiza (AM); cucumber mosaic virus; polyphosphate translocation; transpiration; virus-induced gene silencing (VIGS)