title: The integral membrane protein SEN1 is required for symbiotic nitrogen fixation in Lotus japonicus nodules.
abstract: Legume plants establish a symbiotic association with bacteria called rhizobia, resulting in the formation of nitrogen-fixing root nodules. A Lotus japonicus symbiotic mutant, sen1, forms nodules that are infected by rhizobia but that do not fix nitrogen. Here, we report molecular identification of the causal gene, SEN1, by map-based cloning. The SEN1 gene encodes an integral membrane protein homologous to Glycine max nodulin-21, and also to CCC1, a vacuolar iron/manganese transporter of Saccharomyces cerevisiae, and VIT1, a vacuolar iron transporter of Arabidopsis thaliana. Expression of the SEN1 gene was detected exclusively in nodule-infected cells and increased during nodule development. Nif gene expression as well as the presence of nitrogenase proteins was detected in rhizobia from sen1 nodules, although the levels of expression were low compared with those from wild-type nodules. Microscopic observations revealed that symbiosome and/or bacteroid differentiation are impaired in the sen1 nodules even at a very early stage of nodule development. Phylogenetic analysis indicated that SEN1 belongs to a protein clade specific to legumes. These results indicate that SEN1 is essential for nitrogen fixation activity and symbiosome/bacteroid differentiation in legume nodules.
authors: National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.
authors: Tsuneo
authors: T
authors: Hakoyama
authors: Kaori
authors: K
authors: Niimi
authors: Takeshi
authors: T
authors: Yamamoto
authors: Sawa
authors: S
authors: Isobe
authors: Shusei
authors: S
authors: Sato
authors: Yasukazu
authors: Y
authors: Nakamura
authors: Satoshi
authors: S
authors: Tabata
authors: Hirotaka
authors: H
authors: Kumagai
authors: Yosuke
authors: Y
authors: Umehara
authors: Katja
authors: K
authors: Brossuleit
authors: Thomas R
authors: TR
authors: Petersen
authors: Niels
authors: N
authors: Sandal
authors: Jens
authors: J
authors: Stougaard
authors: Michael K
authors: MK
authors: Udvardi
authors: Masanori
authors: M
authors: Tamaoki
authors: Masayoshi
authors: M
authors: Kawaguchi
authors: Hiroshi
authors: H
authors: Kouchi
authors: Norio
authors: N
authors: Suganuma
mesh_terms: D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D005816:Genetic Complementation Test; D000070116:Lotus / Q000235:genetics / Q000382:microbiology / Q000502:physiology* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009586:Nitrogen Fixation / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D012231:Rhizobium / Q000502:physiology; D053204:Root Nodules, Plant / Q000166:cytology / Q000382:microbiology / Q000502:physiology* / Q000648:ultrastructure; D013559:Symbiosis / Q000235:genetics
chemical_list: D008565:Membrane Proteins; D010940:Plant Proteins