title: A Dicarboxylate Transporter, LjALMT4, Mainly Expressed in Nodules of Lotus japonicus.
abstract: Legume plants can establish symbiosis with soil bacteria called rhizobia to obtain nitrogen as a nutrient directly from atmospheric N2 via symbiotic nitrogen fixation. Legumes and rhizobia form nodules, symbiotic organs in which fixed-nitrogen and photosynthetic products are exchanged between rhizobia and plant cells. The photosynthetic products supplied to rhizobia are thought to be dicarboxylates but little is known about the movement of dicarboxylates in the nodules. In terms of dicarboxylate transporters, an aluminum-activated malate transporter (ALMT) family is a strong candidate responsible for the membrane transport of carboxylates in nodules. Among the seven ALMT genes in the Lotus japonicus genome, only one, LjALMT4, shows a high expression in the nodules. LjALMT4 showed transport activity in a Xenopus oocyte system, with LjALMT4 mediating the efflux of dicarboxylates including malate, succinate, and fumarate, but not tricarboxylates such as citrate. LjALMT4 also mediated the influx of several inorganic anions. Organ-specific gene expression analysis showed LjALMT4 mRNA mainly in the parenchyma cells of nodule vascular bundles. These results suggest that LjALMT4 may not be involved in the direct supply of dicarboxylates to rhizobia in infected cells but is responsible for supplying malate as well as several anions necessary for symbiotic nitrogen fixation, via nodule vasculatures.
authors.affiliation: 1 Research Institute for Sustainable Humanosphere, Kyoto University, Uji 611-0011, Japan;|2 Institute of Mountain Science, Shinshu University, Matsumoto 390-8621, Japan; and.
authors.forename: Kojiro
authors.initials: K
authors.lastname: Takanashi
authors.affiliation: 3 Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sasaki
authors.affiliation: 1 Research Institute for Sustainable Humanosphere, Kyoto University, Uji 611-0011, Japan;
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Kan
authors.affiliation: 1 Research Institute for Sustainable Humanosphere, Kyoto University, Uji 611-0011, Japan;
authors.forename: Yuka
authors.initials: Y
authors.lastname: Saida
authors.affiliation: 1 Research Institute for Sustainable Humanosphere, Kyoto University, Uji 611-0011, Japan;
authors.forename: Akifumi
authors.initials: A
authors.lastname: Sugiyama
authors.affiliation: 3 Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yamamoto
authors.affiliation: 1 Research Institute for Sustainable Humanosphere, Kyoto University, Uji 611-0011, Japan;
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Yazaki
mesh_terms: D029382:Dicarboxylic Acid Transporters / Q000235:genetics* / Q000378:metabolism; D017930:Genes, Reporter; D000070116:Lotus / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012231:Rhizobium / Q000166:cytology / Q000502:physiology*; D053204:Root Nodules, Plant / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D029382:Dicarboxylic Acid Transporters; D010940:Plant Proteins