Norio Suganuma
Publications
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3.59Impact points
The integral membrane protein SEN1 is required for symbiotic nitrogen fixation in Lotus japonicus nodules.
Plant & cell physiology. 11/2011; 53(1):225-36.
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 t... [more] 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.
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3.59Impact points
How many peas in a pod? Legume genes responsible for mutualistic symbioses underground.
Plant & cell physiology. 09/2010; 51(9):1381-97.
The nitrogen-fixing symbiosis between legume plants and Rhizobium bacteria is the most prominent plant-microbe endosymbiotic system and, together with mycorrhizal fungi, has critical importance in agriculture. The introduction of two model legume species, Lotus japonicus and Medicago truncatula, has... [more] The nitrogen-fixing symbiosis between legume plants and Rhizobium bacteria is the most prominent plant-microbe endosymbiotic system and, together with mycorrhizal fungi, has critical importance in agriculture. The introduction of two model legume species, Lotus japonicus and Medicago truncatula, has enabled us to identify a number of host legume genes required for symbiosis. A total of 26 genes have so far been cloned from various symbiotic mutants of these model legumes, which are involved in recognition of rhizobial nodulation signals, early symbiotic signaling cascades, infection and nodulation processes, and regulation of nitrogen fixation. These accomplishments during the past decade provide important clues to understanding not only the molecular mechanisms underlying plant-microbe endosymbiotic associations but also the evolutionary aspects of nitrogen-fixing symbiosis between legume plants and Rhizobium bacteria. In this review we survey recent progress in molecular genetic studies using these model legumes.
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34.48Impact points
Host plant genome overcomes the lack of a bacterial gene for symbiotic nitrogen fixation.
Nature. 11/2009; 462(7272):514-7.
Homocitrate is a component of the iron-molybdenum cofactor in nitrogenase, where nitrogen fixation occurs. NifV, which encodes homocitrate synthase (HCS), has been identified from various diazotrophs but is not present in most rhizobial species that perform efficient nitrogen fixation only in symbio... [more] Homocitrate is a component of the iron-molybdenum cofactor in nitrogenase, where nitrogen fixation occurs. NifV, which encodes homocitrate synthase (HCS), has been identified from various diazotrophs but is not present in most rhizobial species that perform efficient nitrogen fixation only in symbiotic association with legumes. Here we show that the FEN1 gene of a model legume, Lotus japonicus, overcomes the lack of NifV in rhizobia for symbiotic nitrogen fixation. A Fix(-) (non-fixing) plant mutant, fen1, forms morphologically normal but ineffective nodules. The causal gene, FEN1, was shown to encode HCS by its ability to complement a HCS-defective mutant of Saccharomyces cerevisiae. Homocitrate was present abundantly in wild-type nodules but was absent from ineffective fen1 nodules. Inoculation with Mesorhizobium loti carrying FEN1 or Azotobacter vinelandii NifV rescued the defect in nitrogen-fixing activity of the fen1 nodules. Exogenous supply of homocitrate also recovered the nitrogen-fixing activity of the fen1 nodules through de novo nitrogenase synthesis in the rhizobial bacteroids. These results indicate that homocitrate derived from the host plant cells is essential for the efficient and continuing synthesis of the nitrogenase system in endosymbionts, and thus provide a molecular basis for the complementary and indispensable partnership between legumes and rhizobia in symbiotic nitrogen fixation.
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[Host legume genes required for symbiotic nitrogen fixation]
Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme. 09/2006; 51(9):1038-43.
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4.41Impact points
Genetics of symbiosis in Lotus japonicus: recombinant inbred lines, comparative genetic maps, and map position of 35 symbiotic loci.
Molecular plant-microbe interactions : MPMI. 02/2006; 19(1):80-91.
Development of molecular tools for the analysis of the plant genetic contribution to rhizobial and mycorrhizal symbiosis has provided major advances in our understanding of plant-microbe interactions, and several key symbiotic genes have been identified and characterized. In order to increase the ef... [more] Development of molecular tools for the analysis of the plant genetic contribution to rhizobial and mycorrhizal symbiosis has provided major advances in our understanding of plant-microbe interactions, and several key symbiotic genes have been identified and characterized. In order to increase the efficiency of genetic analysis in the model legume Lotus japonicus, we present here a selection of improved genetic tools. The two genetic linkage maps previously developed from an interspecific cross between L. japonicus Gifu and L. filicaulis, and an intraspecific cross between the two ecotypes L. japonicus Gifu and L. japonicus MG-20, were aligned through a set of anchor markers. Regions of linkage groups, where genetic resolution is obtained preferentially using one or the other parental combination, are highlighted. Additional genetic resolution and stabilized mapping populations were obtained in recombinant inbred lines derived by a single seed descent from the two populations. For faster mapping of new loci, a selection of reliable markers spread over the chromosome arms provides a common framework for more efficient identification of new alleles and new symbiotic loci among uncharacterized mutant lines. Combining resources from the Lotus community, map positions of a large collection of symbiotic loci are provided together with alleles and closely linked molecular markers. Altogether, this establishes a common genetic resource for Lotus spp. A web-based version will enable this resource to be curated and updated regularly.
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9.29Impact points
The sulfate transporter SST1 is crucial for symbiotic nitrogen fixation in Lotus japonicus root nodules.
The Plant cell. 06/2005; 17(5):1625-36.
Symbiotic nitrogen fixation (SNF) by intracellular rhizobia within legume root nodules requires the exchange of nutrients between host plant cells and their resident bacteria. Little is known at the molecular level about plant transporters that mediate such exchanges. Several mutants of the model le... [more] Symbiotic nitrogen fixation (SNF) by intracellular rhizobia within legume root nodules requires the exchange of nutrients between host plant cells and their resident bacteria. Little is known at the molecular level about plant transporters that mediate such exchanges. Several mutants of the model legume Lotus japonicus have been identified that develop nodules with metabolic defects that cannot fix nitrogen efficiently and exhibit retarded growth under symbiotic conditions. Map-based cloning of defective genes in two such mutants, sst1-1 and sst1-2 (for symbiotic sulfate transporter), revealed two alleles of the same gene. The gene is expressed in a nodule-specific manner and encodes a protein homologous with eukaryotic sulfate transporters. Full-length cDNA of the gene complemented a yeast mutant defective in sulfate transport. Hence, the gene was named Sst1. The sst1-1 and sst1-2 mutants exhibited normal growth and development under nonsymbiotic growth conditions, a result consistent with the nodule-specific expression of Sst1. Data from a previous proteomic study indicate that SST1 is located on the symbiosome membrane in Lotus nodules. Together, these results suggest that SST1 transports sulfate from the plant cell cytoplasm to the intracellular rhizobia, where the nutrient is essential for protein and cofactor synthesis, including nitrogenase biosynthesis. This work shows the importance of plant sulfate transport in SNF and the specialization of a eukaryotic transporter gene for this purpose.
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4.41Impact points
cDNA macroarray analysis of gene expression in ineffective nodules induced on the Lotus japonicus sen1 mutant.
Molecular plant-microbe interactions : MPMI. 12/2004; 17(11):1223-33.
The Lotus japonicus sen1 mutant forms ineffective nodules in which development is arrested at the stage of bacterial differentiation into nitrogen-fixing bacteroids. Here, we used cDNA macroarray systems to compare gene expression in ineffective nodules induced on the sen1 mutant with gene expressio... [more] The Lotus japonicus sen1 mutant forms ineffective nodules in which development is arrested at the stage of bacterial differentiation into nitrogen-fixing bacteroids. Here, we used cDNA macroarray systems to compare gene expression in ineffective nodules induced on the sen1 mutant with gene expression in wild-type nodules, in order to identify the host plant genes that are involved in nitrogen fixation. Macroarray analysis coupled with Northern blot analysis revealed that the expression of 18 genes was significantly enhanced in ineffective sen1 nodules, whereas the expression of 30 genes was repressed. Many of the enhanced genes encoded hydrolase enzymes, such as cysteine proteinase and asparaginase, that might function in the early senescence of sen1 nodules. By contrast, the repressed genes encoded nodulins, enzymes that are involved in carbon and nitrogen metabolism, membrane transporters, enzymes involved in phytohormone metabolism and secondary metabolism, and regulatory proteins. These proteins might have a role in the establishment of nitrogen fixation. In addition, we discovered two novel genes that encoded glutamate-rich proteins and were localized in the vascular bundles of the nodules. The expression of these genes was repressed in the ineffective nodules, which had lower levels of nitrogenase activity.
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4.92Impact points
Large-scale analysis of gene expression profiles during early stages of root nodule formation in a model legume, Lotus japonicus.
DNA research : an international journal for rapid publication of reports on genes and genomes. 09/2004; 11(4):263-74.
Gene expression profiles during early stages of formation of symbiotic nitrogen-fixing nodules in a model legume Lotus japonicus were analyzed by means of a cDNA array of 18,144 non-redundant expressed sequence tags (ESTs) isolated from L. japonicus. Expression of a total of 1,076 genes was signific... [more] Gene expression profiles during early stages of formation of symbiotic nitrogen-fixing nodules in a model legume Lotus japonicus were analyzed by means of a cDNA array of 18,144 non-redundant expressed sequence tags (ESTs) isolated from L. japonicus. Expression of a total of 1,076 genes was significantly accelerated during the successive stages that represent infection of Mesorhizobium loti, nodule primordium initiation, nodule organogenesis, and the onset of nitrogen fixation. These include 32 nodulin and nodulinhomolog genes as well as a number of genes involved in the catabolism of photosynthates and assimilation of fixed nitrogen that were previously known to be abundantly expressed in root nodules of many legumes. We also identified a large number of novel nodule-specific or enhanced genes, which include genes involved in many cellular processes such as membrane transport, defense responses, phytohormone synthesis and responses, signal transduction, cell wall synthesis, and transcriptional regulation. Notably, our data indicate that the gene expression profile in early steps of Rhizobium-legume interactions is considerably different from that in subsequent stages of nodule development. A number of genes involved in the defense responses to pathogens and other stresses were induced abundantly in the infection process, but their expression was suppressed during subsequent nodule formation. The results provide a comprehensive data source for investigation of molecular mechanisms underlying nodulation and symbiotic nitrogen fixation.
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4.41Impact points
Expression of genes encoding late nodulins characterized by a putative signal peptide and conserved cysteine residues is reduced in ineffective pea nodules.
Molecular plant-microbe interactions : MPMI. 03/2002; 15(2):129-37.
Five nodulin genes, PsN1, PsN6, PsN314, PsN335, and PsN466, with reduced expression in ineffective nodules on the pea (Pisum sativum) mutant E135 (sym13) were characterized. They encode small polypeptides containing a putative signal peptide and conserved cysteine residues and show homology to the n... [more] Five nodulin genes, PsN1, PsN6, PsN314, PsN335, and PsN466, with reduced expression in ineffective nodules on the pea (Pisum sativum) mutant E135 (sym13) were characterized. They encode small polypeptides containing a putative signal peptide and conserved cysteine residues and show homology to the nodulins PsENOD3/14 and PsNOD6. For each gene, multiple bands were detected by genomic Southern analysis. Northern analysis showed that all five genes were expressed exclusively in nodules and that their temporal expression patterns were similar to that of the leghemoglobin (Lb) gene during nodule development. Their transcripts were localized predominantly from the interzone II-III to the distal part of nitrogen-fixing zone III in effective nodules, resembling the Lb gene. However, transcripts in ineffective E135 nodules were localized in narrower regions than those in the effective nodules. These results indicate that these nodulins are abundant in pea nodules and that their successive expression during nodule development is associated with nitrogen-fixing activity.
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Metabolic changes in soybean nodules after inhibition of nitrogen fixation by treatment with oxygen
Metabolites that accumulated in soybean [ Glycine max (L.) Merr.] nodules after inhibition of nitrogen fixation were analysed to determine what carbon compounds the bacteroids might obtain from their host. Exposure of roots of intact soybean plants to 100% O 2 for 5 min caused a decrease in acetylen... [more] Metabolites that accumulated in soybean [ Glycine max (L.) Merr.] nodules after inhibition of nitrogen fixation were analysed to determine what carbon compounds the bacteroids might obtain from their host. Exposure of roots of intact soybean plants to 100% O 2 for 5 min caused a decrease in acetylene reduction activity within 10 min and then the activity recovered only slowly. Analysis of carbohydrates, organic acids, volatile compounds and amino acids in extracts of nodules revealed that succinate, malate and alanine all accumulated within 10 min after treatment with O 2 . The concentrations of sucrose, acetone, tyrosine, valine, isoleucine, leucine, and ornithine in the nodules increased slowly after such treatment. The results are discussed in terms of carbon sources for supporting nitrogen fixation of soybean bacteroids.
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Enhanced production of ethylene by soybean roots after inoculation with Bradyrhizobium japonicum
Plant Science.
The production of ethylene by soybean (Glycine max (L.) Merr.) roots during nodulation was investigated. The production of ethylene by roots was stimulated by inoculation with Bradyrhizobium japonicum. The stimulation of the production of ethylene by the roots of inoculated plants was maximal 3 days... [more] The production of ethylene by soybean (Glycine max (L.) Merr.) roots during nodulation was investigated. The production of ethylene by roots was stimulated by inoculation with Bradyrhizobium japonicum. The stimulation of the production of ethylene by the roots of inoculated plants was maximal 3 days after inoculation and then the rate of production of ethylene fell to that in the roots of uninoculated plants. No enhanced production of ethylene after inoculation was detected with the roots of a non-nodulating soybean mutant or after inoculation with a heterologous rhizobium, Rhizobium leguminosarum bv. viciae. Treatment of roots of wild-type soybean with an inhibitor of ethylene biosynthesis, aminoethoxyvinylglycine (AVG), prevented the enhanced production of ethylene. However, the number of nodules formed on the roots was barely affected by the treatment with AVG. The results indicate that the production of ethylene by soybean roots is transiently enhanced by infection with the homologous rhizobium.
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Bacteroids Isolated from Ineffective Nodules of Pisum sativum Mutant E135 (syml3) Lack Nitrogenase Activity but Contain the Two Protein Components of Nitrogenase
Pea mutant E135 ( sym 15) forms ineffective (Fix−) nodules that lack nitrogen fixing activity. To determine the developmental step blocked in E135 nodules we studied the nitrogenase activities in isolated bacteroids and in cell-free extracts of bacteroids, and measured the two components of nitrogen... [more] Pea mutant E135 ( sym 15) forms ineffective (Fix−) nodules that lack nitrogen fixing activity. To determine the developmental step blocked in E135 nodules we studied the nitrogenase activities in isolated bacteroids and in cell-free extracts of bacteroids, and measured the two components of nitrogenase protein in bacteroids. Bacteroids prepared anaerobically from E135 nodules showed no acetylene reduction activity in the presence and absence of myoglobin. Furthermore, no acetylene reduction activity by cell-free extracts of E135 bacteroids was detected in the presence of ATP-generating system and dithionite. However, immuno-blotting analyses revealed the presence of nitrogenase components I and II in E135 nodule bacteroids. These results suggest that a host plant gene is involved in the expression of nitrogenase activity in symbiotic bacteria.
Following (12)
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Thomas Ott
Ludwig-Maximilians-Universität München -
Takuji Ohyama
Niigata University -
Toshio Aoki
SONY -
Marco Betti
Universidad de Sevilla -
Tomoko Kojima
NARO Institute of Livestock and Grassland Science
Topics (2)
