Shoshi Muto

Nagoya University, Nagoya-shi, Aichi-ken, Japan

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Publications (42)153.99 Total impact

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    ABSTRACT: The cytoplasm around a wound made in the multinucleate unicellular green alga Ventricaria ventricosa ( J. Agardh) Olsen et West formed an aggregation-ring surrounding the wound immediately after injury. A contraction of the ring then brought about wound healing in culture medium containing Ca2+. Involvement of a calcium-dependent protein kinase (CDPK) as a regulator of wound healing was examined using an anti-Dunaliella tertiolecta CDPK antibody. A 52-kDa protein cross-reacting with the antibody was detected by Western blotting. Protein kinases of 60 kDa and 52 kDa, which were markedly activated by Ca2+, and a 40-kDa Ca2+-independent protein kinase were detected by an in-gel protein kinase assay using myelin basic protein as the substrate. A 52-kDa band with Ca2+-dependent protein kinase activity was immunoprecipitated from the cytoplasmic extract, indicating that these 52-kDa proteins are identical and possess CDPK activity. Microscopic observation showed that the contraction of the aggregation ring was suppressed by application of the anti-CDPK to the culture medium. A protein kinase inhibitor, K-252a, and the calmodulin inhibitors, calmidazolium and compound 48 / 80, which inhibit CDPK activity, also suppressed the contraction of the aggregation-ring. Immunofluorescence microscopy showed a similar distribution of 52-kDa CDPK to the distribution of f-actin, which was randomly distributed in an intact cell and formed a bundle during wound healing. Further, f-actin was not recruited after injury in the presence of the antibody to CDPK. These results suggest that the 52-kDa CDPK functions as a Ca2+ receptor in wound healing and simultaneously participates in the organization and contraction of f-actin to heal the wound.
    Journal of Phycology 07/2008; 36(6):1145 - 1152. · 2.53 Impact Factor
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    ABSTRACT: A 26-kDa and a 36-kDa protein that cross-reacted with anti-Ga-common and anti-Gβ antibodies, respectively, were detected in Dunaliella cells. The 26-kDa protein was solubilized from a crude membrane fraction with deoxycholate and purified to homogeneity by DE52 and hydroxylapatite chromatography and DEAE-5PW high performance liquid chromatography (HPLC). The hydroxylapatite-purified preparation had GTPγS binding and GTPase activities, but the homogeneous 26-kDa protein had none. The sequence of the 28 N-terminal amino acids of the 26-kDa protein had no homology to any GTP binding protein thus far reported.
    Physiologia Plantarum 04/2006; 94(3):486 - 490. · 3.26 Impact Factor
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    ABSTRACT: Plants are always exposed to the menace of oxidative stress and protect themselves by activating a variety of defense responses. However, molecular mechanisms for oxidative stress-induced gene expression are largely unknown. We here studied the roles of the oxidative stress-responsive putative voltage-dependent Ca(2+) permeable channels, NtTPC1A and NtTPC1B, and cell cycle in H(2)O(2)-induced expression of antioxidant enzymes, glutathione peroxidase (GPX) and ascorbate peroxidase (APX), in tobacco BY-2 cells. H(2)O(2)-induced [Ca(2+)](cyt) rise and expression of GPX and APX were inhibited by the cosuppression of NtTPC1A/B as well as Al ion, a specific blocker for NtTPC1s, and enhanced by overexpression of AtTPC1, suggesting that NtTPC1s are the major Ca(2+)-permeable channels activated by H(2)O(2) and that Ca(2+) influx via NtTPC1s is involved in induction of H(2)O(2)-triggered gene expression. Oxidative stress-induced signal transduction mechanisms were highly dependent on the phases of the cell cycle; H(2)O(2)-induced [Ca(2+)](cyt) rise and expression of GPX and APX as well as the level of NtTPC1s transcripts correlated with each other and were maximal at G1 phase. In contrast, the cell cycle-dependence of hypoosmotic shock-induced [Ca(2+)](cyt) rise that is known to be independent of NtTPC1s was almost reverse and maximal at S phase. These results suggest that the cell cycle-dependent regulation of oxidative stress-induced [Ca(2+)](cyt) rise and expression of NtTPC1s contribute to the cell cycle dependence of H(2)O(2)-induced expression of peroxidases. Various Ca(2+)-mediated signal transduction pathways are differentially regulated by the cell cycle.
    Biochemical and Biophysical Research Communications 12/2005; 336(4):1259-67. · 2.28 Impact Factor
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    ABSTRACT: The molecular links between the cell cycle and defense responses in plants are largely unknown. Using synchronized tobacco BY-2 cells, we analyzed the cell cycle dependence of elicitor-induced defense responses. In synchronized cultured apoaequorin-expressing cells, the increase in cytosolic free Ca2+ induced by a proteinaceous elicitor, cryptogein, was greatly suppressed during the G2 and M phases in comparison with G1 or S phases. Treatment with cryptogein during the G1 or S phases also induced biphasic (rapid/transient and slow/prolonged) responses in activation of mitogen-activated protein kinases (MAPKs) and production of reactive oxygen species (ROS). In contrast, elicitor treatment during the G2 or M phases induced only a rapid and transient phase of MAPK activation and ROS production. Their slow and prolonged phases as well as expression of defense-related genes, cell cycle arrest and cell death were induced only after the cell cycle progressed to the G1 phase; removal of the elicitor before the start of the G1 phase inhibited these responses. These results suggest that although cryptogein recognition occurred at all phases of the cell cycle, the recognition during the S or G1 phases, but not at the G2 or M phases, induces the prolonged activation of MAPKs and the prolonged production of ROS, followed by cell cycle arrest, accumulation of defense-related gene transcripts and cell death. Elicitor signal transduction depends on the cell cycle and is regulated differently at each phase.
    Plant and Cell Physiology 02/2005; 46(1):156-65. · 4.98 Impact Factor
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    ABSTRACT: Protein kinases are involved in signal transduction for environmental stress responses. In response to drought and salinity, a 48-kDa protein kinase (AAPK; abscisic acid-activated protein kinase (AAPK) in guard cells is activated by abscisic acid (ABA) and phosphorylates several targets such as the carboxy-terminus of inward-rectifying K+ channel and heterogeneous mRNA binding protein to adopt to the changing environment. The AAPK expressed specifically in guard cells, and recombinant AAPK was phosphorylated only with the extract from ABA-treated guard cells but not from untreated cells. This indicates the presence of an AAPK kinase (AAPKK), which is activated by ABA and phosphorylates AAPK preceding the activation of AAPK. Both AAPK and AAPKK are involved in the protein kinase cascade for the rapid ABA-signaling.
    Zeitschrift fur Naturforschung C 01/2005; 60(9-10):769-73. · 0.57 Impact Factor
  • Takuya Furuichi, Shoshi Muto
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    ABSTRACT: Using Ca2+-dependent photoprotein aequorin-transformed tobacco BY-2 cell suspensions, the sugar-induced increase in cytosolic free Ca2+ concentration ([Ca2+]cyt) was investigated by measuring the luminescence intensity. When 0.5 M sucrose or some other sugars were fed to the cells, strong and transient luminescence was observed. Salts or sugar analogues didn't show this effect. In addition, the intensity of sucrose-induced aequorin luminescence was gradually enhanced when cells were exposed to sugar-starvation. This was observed with the concurrent expression of the sucrose/H+ co-transporter, NtSUT1A. The [Ca2+]cyt increase may initiate Ca2+-signaling leading to the expression of genes related to biosynthesis of storage carbohydrates in a sink organ. The sugar-signaling may play an important role in the conversion on nutritional stage of plant tissue, source organ to sink organ.
    Zeitschrift fur Naturforschung C 01/2005; 60(9-10):764-8. · 0.57 Impact Factor
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    ABSTRACT: In plant cells, Al ion plays dual roles as an inducer and an inhibitor of Ca(2+) influx depending on the concentration. Here, the effects of Al on Ca(2+) signaling were assessed in tobacco BY-2 cells expressing aequorin and a putative plant Ca(2+) channel from Arabidopsis thaliana, AtTPC1 (two-pore channel 1). In wild-type cells (expressing only aequorin), Al treatment induced the generation of superoxide, and Ca(2+) influx was secondarily induced by superoxide. Higher Al concentrations inhibited the Al-stimulated and superoxide-mediated Ca(2+) influx, indicating that Ca(2+) channels responsive to reactive oxygen species (ROS) are blocked by high concentration of Al. H(2)O(2)-induced Ca(2+) influx was also inhibited by Al. Thus, inhibitory action of Al against ROS-induced Ca(2+) influx was confirmed. Similarly, known Ca(2+) channel blockers such as ions of La and Gd inhibited the H(2)O(2)-induced Ca(2+) influx. While La also inhibited the hypoosmotically induced Ca(2+) influx, Al showed no inhibitory effect against the hypoosmotic Ca(2+) influx. The effects of Al and La on Ca(2+) influx were also tested in the cell line overexpressing AtTPC1 and the cell line AtTPC1-dependently cosuppressing the endogenous TPC1 equivalents. Notably, responsiveness to H(2)O(2) was lost in the cosuppression cell line, thus TPC1 channels are required for ROS-responsive Ca(2+) influx. Data also suggested that hypoosmotic shock induces TPC1-independent Ca(2+) influx and Al shows no inhibitory action against the TPC1-independent event. In addition, AtTPC1 overexpression resulted in a marked increase in Al-sensitive Ca(2+) influx, indicating that TPC1 channels participate in osmotic Ca(2+) influx only when overexpressed. We concluded that members of TPC1 channel family are the only ROS-responsive Ca(2+) channels and are the possible targets of Al-dependent inhibition.
    Biochemical and Biophysical Research Communications 12/2004; 324(1):40-5. · 2.28 Impact Factor
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    ABSTRACT: By searching a Chlamydomonas expressed sequence tag database and by comparing the retrieved data with homologous sequences from a DNA database, we identified an expressed Chlamydomonas reinhardtii putative major intrinsic protein (MIP) gene. The nucleotide sequence, consisting of 1,631 bp, contains an open reading frame coding for a 300-amino-acid protein named CrMIP1. It possesses conserved NPA motifs, but is not highly homologous to known aquaporins. CrMIP1 was expressed in Saccharomyces cerevisiae and assayed for water and glycerol transport activity. By the stopped-flow spectrophotometric assay, CrMIP1 did not enhance the osmotic water permeability of membrane vesicles of the yeast transformant. However, the transformant cells showed glycerol transport activity in the in vivo assay using [14C]glycerol. This is the first report on the isolation and functional identification of a MIP member from algae.
    Plant and Cell Physiology 10/2004; 45(9):1313-9. · 4.98 Impact Factor
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    ABSTRACT: Ca(2+) is the pivotal second messenger for induction of defense responses induced by treatment of pathogen-derived elicitor or microbial infection in plants. However, molecular bases for elicitor-induced generation of Ca(2+) signals (Ca(2+) transients) are largely unknown. We here identified cDNAs for putative voltage-dependent Ca(2+)-permeable channels, NtTPC1A and NtTPC1B, that are homologous to TPC1 (two pore channel) from suspension-cultured tobacco BY-2 cells. NtTPC1s complemented the growth of a Saccharomyces cerevisiae mutant defective in CCH1, a putative Ca(2+) channel, in a low Ca(2+) medium, suggesting that both products permeate Ca(2+) through the plasma membrane. Cosuppression of NtTPC1s in apoaequorin-expressing BY-2 cells resulted in inhibition of rise in cytosolic free Ca(2+) concentration ([Ca(2+)](cyt)) in response to sucrose and a fungal elicitor cryptogein, while it did not affect hypoosmotic shock-induced [Ca(2+)](cyt) increase. Cosuppression of NtTPC1s also caused suppression of cryptogein-induced programmed cell death and defense-related gene expression. These results suggest that NtTPC1s are involved in Ca(2+) mobilization induced by the cryptogein and sucrose, and have crucial roles in cryptogein-induced signal transduction pathway.
    Biochemical and Biophysical Research Communications 06/2004; 317(3):823-30. · 2.28 Impact Factor
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    ABSTRACT: Ion fluxes and the production of reactive oxygen species (ROS) are early events that follow elicitor treatment or microbial infection. However, molecular mechanisms for these responses as well as their relationship have been controversial and still largely unknown. We here simultaneously monitored the temporal sequence of initial events at the plasma membrane in suspension-cultured tobacco cells (cell line BY-2) in response to a purified proteinaceous elicitor, cryptogein, which induced hypersensitive cell death. The elicitor induced transient rise in cytosolic Ca(2+) concentration ([Ca(2+)](cyt)) showing two distinct peaks, followed by biphasic (rapid/transient and slow/prolonged) Cl(-) efflux and H(+) influx. Pharmacological analyses suggested that the two phases of the [Ca(2+)](cyt) response correspond to Ca(2+) influx through the plasma membrane and an inositol 1,4,5-trisphophate-mediated release of Ca(2+) from intracellular Ca(2+) stores, respectively, and the [Ca(2+)](cyt) transients and the Cl(-) efflux were mutually dependent events regulated by protein phosphorylation. The elicitor also induced production of ROS including (*)O(2)(-) and H(2)O(2), which initiated after the [Ca(2+)](cyt) rise and required Ca(2+) influx, Cl(-) efflux and protein phosphorylation. An inhibitor of NADPH oxidase, diphenylene iodonium, completely inhibited the elicitor-induced production of (*)O(2)(-) and H(2)O(2), but did not affect the [Ca(2+)](cyt) transients. These results suggest that cryptogein-induced plasma membrane Ca(2+) influx is independent of ROS, and NADPH oxidase dependent ROS production is regulated by these series of ion fluxes.
    Plant and Cell Physiology 03/2004; 45(2):160-70. · 4.98 Impact Factor
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    ABSTRACT: acid (SA) that was named after Salix plant (willow), was first discovered as a major component in the extracts from willow tree bark that had been used as a natural anti-inflammatory drug from the ancient time to the 18 th century (Rainsford 1984; Weissman 1991). Acetylsalicylic acid which is widely known as aspirin is the world first synthetic drug that had been produced by Bayer Company as anti-inflammatory agent in 1897 (Weissman 1991). Since then aspirin became one of the most popular drugs among the people and has been widely used for over 100 years, and pharmacological actions of aspirin and related salicylates in animal system have been intensively studied while only little about the action of SA in plants has been elucidated. White (1979) was the first plant biologist paid attention to salicylates as disease resistance-inducing chemicals. He and his colleague demonstrated that injection of aspirin into tobacco leaves enhanced the resistance to subsequent infection by tobacco mosaic virus (TMV) (White 1979; Antoniw and White 1980). Later, it has been shown that this treatment induces the accumulation of pathogenesis-related (PR) proteins (Kessmann and Ryals 1993; Malamy et al. 1990; Métraux et al. 1990). Recent intensive studies have shown that SA biosynthesis and signaling required for plant defense should not be regarded as a linear pathway but rather as a complex network (Shah 2003). This article describes the recent progress in our understanding of SA signaling and biosynthesis leading to a controlled level of SA in plants, by covering historical milestone works. Until now, involvement of SA signaling was com-monly confirmed by the phenotypes of plants carrying the NahG transgene encoding bacterial salicylate hydroxylase which converts SA to catechol (Delaney et al. 1994; Hunt et al. 1996; Alvarez 2000). Lowered non-host resistance to a Pseudomonas syringae pv. phaseolicola strain is one of the representative NahG phenotype reported for NahG Arabidopsis plants, but a recent report presented the data questioning above effect of NahG and also reliability of NahG experiments judging the involvement of SA was very much weakened (van Wees et al. 2003). The report uncovered that the by-product of NahG action, catechol may be the actual player lowering the non-host resistance to the pathogen. The report propounded that any conclusion about SA requirement based solely on phenotypes of NahG plants should be reevaluated. Further investigations on NahG side effects are urgently required for evaluation of the earlier works using NahG plants. In contrast, the works directly blocking the SA biosynthesis for examining the SA requirement in defense response (e.g. Nawrath and Métraux 1999; Wildermuth et al. 2001) must receive
    Plant Biotechnology 01/2004; 21(5):319--335. · 0.94 Impact Factor
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    ABSTRACT: Salicylic acid beta-glucoside (SAG) is a storage form of a defense signal against pathogens, releasing free salicylic acid (SA), to meet the requirements in plants. Since excess SA induces locally restricted cell death following oxidative burst and Ca2+ influx in plants, the effects of SAG on cell viability, Ca2+ influx, and generation of superoxide (O2*-) were examined in suspension-cultured tobacco BY-2 cells expressing aequorin. Among SA-related chemicals tested, only SAG induced the slow and long-lasting O2*- generation, although SAG was less active in acute O2*- generation, Ca2+ influx and induction of cell death. The prolonging action of SAG is likely due to gradual release of SA and the data suggested that a peroxidase-dependent reaction is involved. Notably, pretreatment with low-dose SA (50 micromu) enhanced the response to SAG by 2.5-fold. There are four possible secondary messengers in early SA signaling detectable in the BY-2 culture, namely O2*-, H2O2, Ca2+ and protein kinase (PK). If these messengers are involved in the low-dose SA-dependent priming for SAG response, they should be inducible by low-dose SA. Among the four SA-inducible signaling events, PK activation was excluded from the low-dose SA action since a much higher SA dose (> 0.4 mmu) was required for PK activation.
    Zeitschrift fur Naturforschung C 01/2004; 59(9-10):684-92. · 0.57 Impact Factor
  • Takuya Furuichi, Shoshi Muto
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    ABSTRACT: . Changes in the cytosolic concentration of calcium ions ([Ca2+]i) play a key second messenger role in signal transduction. These changes are visualized by making use of either Ca2+-sensitive fluorescent dyes or the Ca2+-sensitive photoprotein, aequorin. Here we describe the advances made over the last 10 years or so, which have conclusively demonstrated a second messenger role for [Ca2+]i in a few model plant systems. Characteristic changes in [Ca2+]i have been seen to precede the responses of plant cells and whole plants to physiological stimuli. This has had a major impact on our understanding of cell signaling in plants. The next challenge will be to establish how the Ca2+ signals are encrypted and decoded in order to provide specificity, and we discuss the current understanding of how this may be achieved.
    Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme 12/2003; 48(15 Suppl):2014-21.
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    ABSTRACT: SUMMARYA cDNA (DtNDK1) encoding a nucleoside diphosphate (NDP) kinase with a putative mitochondrial targeting signal sequence was previously isolated from the halo-tolerant green alga Dunaliella tertiolecta. When expressed in Saccharomyces cerevisiae, the processed DtNDK1 enzyme was specifically localized to mitochondria. The present study reports several biochemical characteristics of the mitochondrial NDP kinase from D. tertiolecta. The mature protein was expressed as either N- or C-terminal hexahistidine-tagged protein and purified to homogeneity by affinity chromato-graphy. Native gel electrophoresis and sedimentation velocity in sucrose density gradients showed that the active enzyme consisted of a hexamer. The enzyme, with a pH optimum of 7, showed the highest specificity to dCDP (Km= 50 μmol/L) and the highest turnover towards the synthesis of UTP (up to 140-fold higher). The present study also provides evidence that purified DtNDK1 proteins are capable of transferring a phosphate group to another protein.
    Phycological Research 08/2003; 51(3):147 - 153. · 1.09 Impact Factor
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    ABSTRACT: Trivalent cations such as those of Al, La, and Gd are phytotoxic. Our previous works showed that addition of LaCl(3) or GdCl(3) to tobacco cells triggers the generation of superoxide (O(2)*-). Here, we show that AlCl(3) at normal physiological pH (5.8) induces much greater production of O(2)*- (detected with a specific chemiluminescence probe), indicating that these trivalent cations similarly induce the oxidative bursts. It was shown that NADPH oxidase is involved in the generation of O(2)*- and the yield of O(2)*- was dose-dependent (ca. 6mM Al, optimal). Following the acute spike of O(2)*-, a gradual increase in cytosolic-free Ca(2+) concentration ([Ca(2+)](c)) was detected with the luminescence of recombinant aequorin over-expressed in the cytosol. Interestingly, a O(2)*- scavenger and a Ca(2+) chelator significantly lowered the level of [Ca(2+)](c) increase, indicating that the Al-induced O(2)*- stimulates the influx of Ca(2+). Compared to the induction of O(2)*- generation, the [Ca(2+)](c) elevation was shown to be maximal (340 nM) at relatively lower Al concentrations (ca. 1.25 mM). Thus, the Al concentration optimal for O(2)*- is too much (inhibitory) for [Ca(2+)](c). In addition, high concentrations of Al were shown to be inhibitory to the H(2)O(2)-induced Ca(2+) influx. This explains the ineffectiveness of high Al concentration in the oxidative burst-mediated induction of [Ca(2+)](c) increase. It is likely that Al-induced [Ca(2+)](c) elevation is manifested from the finely geared balance between the O(2)*- -mediated driving force and the channel inhibition-mediated brake. Furthermore, it is note-worthy that Al (< or =10mM) showed no inhibitory effect on the hypo-osmolarity-induced Ca(2+) influx, implying that Al may be a selective inhibitor of redox-responsive Ca(2+) channels. Possible target channels of Al actions are discussed.
    Biochemical and Biophysical Research Communications 08/2003; 308(1):35-42. · 2.28 Impact Factor
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    ABSTRACT: We isolated a full-length cDNA encoding a nucleoside diphosphate (NDP) kinase from a Dunaliella tertiolecta cDNA library by homology cloning and rapid amplification of cDNA ends-PCR. The cDNA sequence, consisting of 840 bp, contained an open reading frame coding for a 221-amino acid protein. The predicted 24-kDa protein was named DtNDK1. It possesses all the residues involved in nucleotide binding and catalysis and, in its long N-terminus, contains putative mitochondrial targeting peptides. The full-length pre-protein expressed in Escherichia coli as a recombinant N-terminally His-tagged protein was retained in inclusion bodies, totally devoid of NDP kinase activity. Upon expression in yeast cells, the full-length protein His-tagged at the C-terminus was found processed in a soluble form that was lacking the first 67 amino acids from the N-terminus. The mature protein, which was purified by affinity chromatography to near homogeneity, showed NDP kinase activity. Confocal microscopy on yeast cells expressing the recombinant protein revealed the specific mitochondrial localization of DtNDK1 labeled at the C-terminus with green fluorescent protein.
    Plant and Cell Physiology 12/2002; 43(11):1276-84. · 4.98 Impact Factor
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    ABSTRACT: Hemoglobin (Hb) solution-based blood substitutes are being developed as oxygen-carrying agents for the prevention of ischemic tissue damage and low blood volume-shock. However, the cell-free Hb molecule has intrinsic toxicity to the tissue since harmful reactive oxygen species (ROS) are readily produced during autoxidation of Hb from the ferrous state to the ferric state, and the cell-free Hb also causes distortion in the oxidant/antioxidant balance in the tissues. There may be further hindering dangers in the use of free Hb as a blood substitute. It has been reported that Hb has peroxidase-like activity oxidizing peroxidase substrates such as aromatic amines. Here we observed the Hb-catalyzed ROS production coupled to oxidation of a neurotransmitter precursor, beta-phenylethylamine (PEA). Addition of PEA to Hb solution resulted in generation of superoxide anion (O2*-). We also observed that PEA increases the Hb-catalyzed monovalent oxidation of ascorbate to ascorbate free radicals (Asc'). The O2*- generation and Asc formation were detected by O2*--specific chemiluminescence of the Cypridina lucigenin analog and electron spin resonance spectroscopy, respectively. PEA-dependent O2*- production and monovalent oxidation of ascorbate in the Hb solution occurred without addition of H2O2, but a trace of H2O2 added to the system greatly increased the production of both O2*- and Asc*. Addition of GSH completely inhibited the PEA-dependent production of O2*- and Asc* in Hb solution. We propose that the O2*- generation and Asc* formation in the Hb solution are due to the pseudoperoxidase activity-dependent oxidation of PEA and resultant ROS may damage tissues rich in monoamines, if the Hb-based blood substitutes were circulated without addition of ROS scavengers such as thiols.
    Bioscience Biotechnology and Biochemistry 07/2002; 66(6):1224-32. · 1.21 Impact Factor
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    ABSTRACT: Beta-phenylethylamine (PEA) induced an increase in cytosolic free calcium ion concentration ([Ca2+]c) in Saccharomyces cerevisiae cells monitored with transgenic aequorin, a Ca2+-dependent photoprotein. The PEA-induced [Ca2+]c increase was dependent on the concentrations of PEA applied, and the Ca2+ mostly originated from an extracellular source. Preceding the Ca2+ influx, H2O2 was generated in the cells by the addition of PEA. Externally added H2O2 also induced a [Ca2+]c increase. These results suggest that PEA induces the [Ca2+]c increase via H2O2 generation. The PEA-induced [Ca2+]c increase occurred in the mid1 mutant with a slightly smaller peak than in the wild-type strain, indicating that Mid1, a stretch-activated nonselective cation channel, may not be mainly involved in the PEA-induced Ca2+ influx. When PEA was applied, the MATa mid1 mutant was rescued from alpha-factor-induced death in a Ca2+-limited medium, suggesting that the PEA-induced [Ca2+]c increase can reinforce calcium signaling in the mating pheromone response pathway.
    Bioscience Biotechnology and Biochemistry 06/2002; 66(5):1069-74. · 1.21 Impact Factor
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    ABSTRACT: Salts at high concentrations may cause oxidative damage to plant cells since many studies indicated the involvement of reactive oxygen species in salt-stress response. Recently, we have demonstrated that treatment of tobacco (Nicotiana tabacum) cell suspension culture with various salts result in an immediate burst of superoxide production via activation of NADPH oxidase by ions of alkali metals (Li+, Na+, K+), alkali earth metals (Mg2+, Ca2+) or lanthanides (La3+, Gd3+). In this study, we tested the effect of extracellular supplementation of Zn2+ and Mn2+ on the cation-induced oxidative burst in tobacco cell suspension culture, measured with a superoxide-specific Cypridina luciferin-derived chemiluminescent reagent. Extracellular supplementation of Zn2+ and Mn2+ inhibited the generation of superoxide in response to addition of salts. Although both Zn2+ and Mn2+ inhibited the salt-induced generation of superoxide, the modes of inhibition by those ions seemed to be different since Mn2+ simply inhibited total production of superoxide while Zn2+ inhibited the early phase of superoxide production and induced the slow release of superoxide. Roles of Mn2+ and Zn2+ in protection of plant cells from salt stress, as an effective superoxide scavenger and an effective inhibitor of plasma membrane-bound NADPH oxidase, respectively, are discussed.
    Physiologia Plantarum 04/2002; 114(3):395-404. · 3.26 Impact Factor
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    ABSTRACT: We obtained spectroscopic evidence in support of salicylate-dependent inactivation of horseradish peroxidase-C. Addition of salicylate to the enzyme arrested at a temporal inactive state (Compound III) in the presence of H2O2, resulted in rapid and irreversible inactivation of the enzyme yielding verdohemoproteins (P-670). Multiple roles for salicylate in peroxidase-catalyzed reactions are discussed.
    Bioscience Biotechnology and Biochemistry 04/2002; 66(3):646-50. · 1.21 Impact Factor

Publication Stats

1k Citations
153.99 Total Impact Points


  • 1997–2008
    • Nagoya University
      • • Graduate School of Bio-Agricultural Sciences
      • • Graduate School of Medicine
      Nagoya-shi, Aichi-ken, Japan
  • 2004–2005
    • Tokyo University of Science
      • Department of Applied Biological Science
      Tokyo, Tokyo-to, Japan
  • 2003–2004
    • Kitakyushu University
      • Graduate School of Environmental Engineering
      Kitakyūshū, Fukuoka-ken, Japan
  • 2002
    • French National Institute for Agricultural Research
      Lutetia Parisorum, Île-de-France, France
    • Hiroshima University
      • Division of Biological Science
      Hiroshima-shi, Hiroshima-ken, Japan