Maki Nagata

Publications (9)28.44 Total impact

• Article: Characterization of Nitric Oxide-Inducing Lipid A Derived from Mesorhizobium loti Lipopolysaccharide.

  Masahito Hashimoto, Youhei Tanishita, Yasuo Suda, Ei-Ichi Murakami, Maki Nagata, Ken-Ichi Kucho, Mikiko Abe, Toshiki Uchiumi
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  ABSTRACT: Mesorhizobium loti is a member of the rhizobia and forms nitrogen-fixing symbioses with several Lotus species. Recently, it was reported that M. loti bacterial cells and their lipopolysaccharide (LPS) preparations transiently induced nitric oxide (NO) production in the roots of L. japonicus. We subsequently found that polysaccharides and the lipid A moiety were responsible for this NO induction. In this study, we elucidated the chemical structure of M. loti lipid A and characterized its NO-inducing activity in response to structural modifications. M. loti LPS were partially hydrolyzed with hydrazine or aqueous hydrofluoric acid to obtain O-deacylated or dephosphorylated LPS, respectively. The untreated and treated LPS fractions were subjected to weak acid hydrolysis to obtain lipid A fractions. The chemical structure of M. loti lipid A was elucidated by chemical composition analysis, MALDI-TOF-MS, and NMR spectra to be P-4-β-GlcNN(1-6)α-GlcNN(1-1)α-GalA, in which positions 2 and 3 of β-GlcNN are substituted for 3-acyloxy-fatty amides, and positions 2 and 3 of α-GlcNN are substituted for 3OH-fatty amides. The partial hydrolysis of lipid A appeared to reduce its NO-inducing activity. These results suggest that L. japonicus root cells recognize the lipid A structure as a means of controlling NO production.
  Microbes and Environments 10/2012; · 1.91 Impact Factor
• Article: Nitric oxide production induced in roots of Lotus japonicus by lipopolysaccharide from Mesorhizobium loti.

  Ei-ichi Murakami, Maki Nagata, Yoshikazu Shimoda, Ken-ichi Kucho, Shiro Higashi, Mikiko Abe, Masahito Hashimoto, Toshiki Uchiumi
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  ABSTRACT: Lipopolysaccharide (LPS) is a bacterial molecule that induces nitric oxide (NO) production and triggers defense systems in plant-pathogen interactions. NO production is induced in the roots of Lotus japonicus after inoculation of the roots with its microsymbiont Mesorhizobium loti. However, the rhizobial molecule that induces NO production has not yet been identified. We investigated NO production in the roots of L. japonicus by treatment with LPS of M. loti. LPS was prepared by phenol-hot water extraction and separated into several fractions: polysaccharide, lipooligosaccharide, oligosaccharide and lipid A. In the roots of L. japonicus, NO production was observed with an NO-specific fluorescent dye 4, 10 and 24 h after treatment with each fraction of LPS. NO production was detected 4 h after treatment with all fractions. NO production was also detectable 24 h after treatment, except after treatment with the polysaccharide and oligosaccharide fractions. Expression of a class 1 hemoglobin gene and application of an NO scavenger showed that the treatment with LPS and LOS induced a similar response to inoculation with M. loti. These data suggest that LPS of M. loti induces NO production after inoculation with M. loti.
  Plant and Cell Physiology 02/2011; 52(4):610-7. · 4.70 Impact Factor
• Source

  Available from: Ann M. Hirsch

  Article: Effect of abscisic acid on symbiotic nitrogen fixation activity in the root nodules of Lotus japonicus.

  Akiyoshi Tominaga, Maki Nagata, Koichi Futsuki, Hidetoshi Abe, Toshiki Uchiumi, Mikiko Abe, Ken-ichi Kucho, Masatsugu Hashiguchi, Ryo Akashi, Ann Hirsch, Susumu Arima, Akihiro Suzuki
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  ABSTRACT: The phytohormone abscisic acid (ABA) is known to be a negative regulator of legume root nodule formation. By screening Lotus japonicus seedlings for survival on an agar medium containing 70 μM ABA, we obtained mutants that not only showed increased root nodule number, but also enhanced nitrogen fixation. The mutant was designated enf1 (enhanced nitrogen fixation 1) and was confirmed to be monogenic and incompletely dominant. In long-term growth experiments with M. loti, although some yield parameters were the same for both enf1 and wild-type plants, both the dry weight and N content of 100 seeds and entire enf1 plants were significantly larger compared than those traits in wild-type seeds and plants. The augmentation of the weight and N content of the enf1 plants most likely reflects the increased N supplied by the additional enf1 nodules and the concomitant increase in N fixation activity. We determined that the endogenous ABA concentration and the sensitivity to ABA of enf1 were lower than that of wild-type seedlings. When wild-type plants were treated with abamine, a specific inhibitor of 9-cis-epoxycarotenoid dioxygenase (NCED), which results in reduced ABA content, the N fixation activity of abamine-treated plants was elevated to the same levels as enf1. We also determined that production of nitric oxide (NO) in enf1 nodules was decreased. We conclude that endogenous ABA concentration not only regulates nodulation, but also nitrogen fixation activity by decreasing NO production in nodules.
  Plant signaling & behavior 04/2010; 5(4):440-3.
• Source

  Available from: Ann M. Hirsch

  Article: Enhanced nodulation and nitrogen fixation in the abscisic acid low-sensitive mutant enhanced nitrogen fixation1 of Lotus japonicus.

  Akiyoshi Tominaga, Maki Nagata, Koichi Futsuki, Hidetoshi Abe, Toshiki Uchiumi, Mikiko Abe, Ken-ichi Kucho, Masatsugu Hashiguchi, Ryo Akashi, Ann M Hirsch, Susumu Arima, Akihiro Suzuki
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  ABSTRACT: The phytohormone abscisic acid (ABA) is known to be a negative regulator of legume root nodule formation. By screening Lotus japonicus seedlings for survival on an agar medium containing 70 microM ABA, we obtained mutants that not only showed increased root nodule number but also enhanced nitrogen fixation. The mutant was designated enhanced nitrogen fixation1 (enf1) and was confirmed to be monogenic and incompletely dominant. The low sensitivity to ABA phenotype was thought to result from either a decrease in the concentration of the plant's endogenous ABA or from a disruption in ABA signaling. We determined that the endogenous ABA concentration of enf1 was lower than that of wild-type seedlings, and furthermore, when wild-type plants were treated with abamine, a specific inhibitor of 9-cis-epoxycarotenoid dioxygenase, which results in reduced ABA content, the nitrogen fixation activity of abamine-treated plants was elevated to the same levels as enf1. We also determined that production of nitric oxide in enf1 nodules was decreased. We conclude that endogenous ABA concentration not only regulates nodulation but also nitrogen fixation activity by decreasing nitric oxide production in nodules.
  Plant physiology 09/2009; 151(4):1965-76. · 6.53 Impact Factor
• Article: A possible role of class 1 plant hemoglobin at the early stage of legume-rhizobium symbiosis.

  Maki Nagata, Masahito Hashimoto, Ei-ichi Murakami, Yoshikazu Shimoda, Fuyuko Shimoda-Sasakura, Ken-ichi Kucho, Akihiro Suzuki, Mikiko Abe, Shiro Higashi, Toshiki Uchiumi
  Plant signaling & behavior 04/2009; 4(3):202-4.
• Article: Expression of a class 1 hemoglobin gene and production of nitric oxide in response to symbiotic and pathogenic bacteria in Lotus japonicus.

  Maki Nagata, Ei-ichi Murakami, Yoshikazu Shimoda, Fuyuko Shimoda-Sasakura, Ken-ichi Kucho, Akihiro Suzuki, Mikiko Abe, Shiro Higashi, Toshiki Uchiumi
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  ABSTRACT: Symbiotic nitrogen fixation by the collaboration between leguminous plants and rhizobia is an important system in the global nitrogen cycle, and some molecular aspects during the early stage of host-symbiont recognition have been revealed. To understand the responses of a host plant against various bacteria, we examined expression of hemoglobin (Hb) genes and production of nitric oxide (NO) in Lotus japonicus after inoculation with rhizobia or plant pathogens. When the symbiotic rhizobium Mesorhizobium loti was inoculated, expression of LjHb1 and NO production were induced transiently in the roots at 4 h after inoculation. In contrast, inoculation with the nonsymbiotic rhizobia Sinorhizobium meliloti and Bradyrhizobium japonicum induced neither expression of LjHb1 nor NO production. When L. japonicus was inoculated with plant pathogens (Ralstonia solanacearum or Pseudomonas syringae), continuous NO production was observed in roots but induction of LjHb1 did not occur. These results suggest that modulation of NO levels and expression of class 1 Hb are involved in the establishment of the symbiosis.
  Molecular Plant-Microbe Interactions 10/2008; 21(9):1175-83. · 4.43 Impact Factor
• Article: Overexpression of class 1 plant hemoglobin genes enhances symbiotic nitrogen fixation activity between Mesorhizobium loti and Lotus japonicus.

  Yoshikazu Shimoda, Fuyuko Shimoda-Sasakura, Ken-ichi Kucho, Norihito Kanamori, Maki Nagata, Akihiro Suzuki, Mikiko Abe, Shiro Higashi, Toshiki Uchiumi
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  ABSTRACT: Plant hemoglobins (Hbs) have been divided into three groups: class 1, class 2, and truncated Hbs. The various physiological functions of class 1 Hb include its role as a modulator of nitric oxide (NO) levels in plants. To gain more insight into the functions of class 1 Hbs, we investigated the physical properties of LjHb1 and AfHb1, class 1 Hbs of a model legume Lotus japonicus and an actinorhizal plant Alnus firma, respectively. Spectrophotometric analysis showed that the recombinant form of the LjHb1 and AfHb1 proteins reacted with NO. The localization of LjHb1 expression was correlated with the site of NO production. Overexpression of LjHb1 and AfHb1 by transformed hairy roots caused changes in symbiosis with rhizobia. The number of nodules formed on hairy roots overexpressing LjHb1 or AfHb1 increased compared with that on untransformed hairy roots. Furthermore, nitrogenase activity as acetylene-reduction activity (ARA) of LjHb1- or AfHb1-overexpressing nodules was higher than that of the vector control nodules. Microscopic observation with a NO-specific fluorescent dye suggested that the NO level in LjHb1- and AfHb1-overexpressing nodules was lower than that of control nodules. Exogenous application of a NO scavenger enhanced ARA in L. japonicus nodules, whereas a NO donor inhibited ARA. These results suggest that the basal level of NO in nodules inhibits nitrogen fixation, and overexpression of class 1 Hbs enhances symbiotic nitrogen fixation activity by removing NO as an inhibitor of nitrogenase.
  The Plant Journal 10/2008; 57(2):254-63. · 6.16 Impact Factor
• Article: Symbiotic rhizobium and nitric oxide induce gene expression of non-symbiotic hemoglobin in Lotus japonicus.

  Yoshikazu Shimoda, Maki Nagata, Akihiro Suzuki, Mikiko Abe, Shusei Sato, Tomohiko Kato, Satoshi Tabata, Shiro Higashi, Toshiki Uchiumi
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  ABSTRACT: We characterized the expression profiles of LjHb1 and LjHb2, non-symbiotic hemoglobin (non-sym-Hb) genes of Lotus japonicus. Although LjHb1 and LjHb2 showed 77% homology in their cDNA sequences, LjHb2 is located in a unique position in the phylogenetic tree of plant Hbs. The 5'-upstream regions of both genes contain the motif AAAGGG at a position similar to that in promoters of other non-sym-Hb genes. Expression profiles obtained by using quantitative RT-PCR showed that LjHb1 and LjHb2 were expressed in all tissues of mature plants, and expression was enhanced in mature root nodules. LjHb1 was strongly induced under both hypoxic and cold conditions, and by the application of nitric oxide (NO) donor, whereas LjHb2 was induced only by the application of sucrose. LjHb1 was also induced transiently by the inoculation with the symbiotic rhizobium Mesorhizobium loti MAFF303099. Observations using fluorescence microscopy revealed the induction of LjHb1 expression corresponded to the generation of NO. These results suggest that non-sym-Hb and NO have important roles in stress adaptation and in the early stage of legume-rhizobium symbiosis.
  Plant and Cell Physiology 02/2005; 46(1):99-107. · 4.70 Impact Factor
• Article: Symbiotic Rhizobium and Nitric Oxide Induce Gene Expression of Nonsymbiotic Hemoglobin in Lotus japonicus

  Yoshikazu Shimoda, Maki Nagata, Akihiro Suzuki, Mikiko Abe, Shusei Sato, Tomohiko Kato, Satoshi Tabata, Shiro Higashi, Toshiki Uchiumi
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  ABSTRACT: We characterized the expression profiles of LjHb1 and LjHb2 , nonsymbiotic hemoglobin (nonsym-Hb) genes of Lotus japonicus . Although LjHb1 and LjHb2 showed 77% homology in their cDNA sequences, LjHb2 is located in a unique position in the phylogenetic tree of plant Hbs. The 5'-upstream regions of both genes contain the motif AAAGGG at a position similar to that in promoters of other nonsym-Hb genes. Expression profiles obtained by using quantitative RT-PCR showed that LjHb1 and LjHb2 were expressed in all tissues of mature plants, and expression was enhanced in mature root nodules. LjHb1 was strongly induced under both hypoxic and cold conditions, and by the application of nitric oxide (NO) donor, whereas LjHb2 was induced only by the application of sucrose. LjHb1 was also induced transiently by the inoculation with the symbiotic rhizobium Mesorhizobium loti MAFF303099. A candidate gene for pathogen-inducible NO synthase (iNOS) of L. japonicus was also induced by inoculation with M. loti MAFF303099. Observations using fluorescence microscopy revealed the induction of LjHb1 expression is corresponded to the generation of NO. These results suggest that nonsym-Hb and NO may have important roles in stress adaptation and in the early stage of legume-rhizobium symbiosis.