Faculty Profiles - MURATA Yoshiyuki

Papers - MURATA Yoshiyuki

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Simple determination of trace amounts of anionic surfactants in river water by spectrophotometry combined with solid-phase extraction. International journal

Masakazu Tsukamoto, Yoshiyuki Murata, Mikiro Tada, Yasuaki Shimoishi

Bioscience, biotechnology, and biochemistry 68 ( 4 ) 920 - 3 2004.4

Language：English Publishing type：Research paper (scientific journal)

A simple and sensitive spectrophotometric method combined with solid-phase extraction (SPE) for the simultaneous determination of sodium linear-dodecylbenzenesulfonate (DBS) and sodium dodecyl sulfate (SDS) is described. The C2 (ethyl group bonded silicagel) cartridge could be repeatedly used more than 500 times for SPE, and it enabled the anionic surfactants to be concentrated by 50-fold. The calibration graph for DBS was linear in the range from 1.6 x 10(-8) M to 5.0 x 10(-7) M and for SDS from 2.0 x 10(-9) M to 3.0 x 10(-7) M. The relative standard deviation (n=5) for 5.0 x 10(-7) M DBS was 3.1% and for 2.5 x 10(-7) M SDS was 1.7%. The proposed method was applied to the simultaneous determination of DBS and SDS in river-water samples.

Degradation of ethyl docosahexaenoate by gamma-ray irradiation and suppression of this degradation by antioxidants. International journal

Yoshiyuki Murata, Ken-ichi Osaki, Yasuaki Shimoishi, Naomichi Baba, Mikiro Tada

Bioscience, biotechnology, and biochemistry 68 ( 3 ) 743 - 5 2004.3

Language：English Publishing type：Research paper (scientific journal)

Ethyl 4,7,10,13,16,19-docosahexaenoate (DHA-Et) dissolved in an ethanol solution or embedded in liposomes was degraded by irradiating with gamma rays in a dose-dependent manner. The degradation rate of DHA-Et embedded in liposomes was higher than that of DHA-Et dissolved in ethanol. Antioxidants suppressed the degradation of DHA-Et embedded in liposomes, the order of activity of the antioxidants being luteolin>fisetin>kaempferol>quercetin>rutin. These results suggest that the hydrophobicity (logP) of an antioxidant is one of determinants for antioxidative activity, but that a vicinal diol structure in the B ring is not favorable for the antioxidative activity.

Inhibitory effects of esculetin on melanin biosynthesis.

Yukimitsu Masamoto, Yoshiyuki Murata, Kimiye Baba, Yasuaki Shimoishi, Mikiro Tada, Kyoya Takahata

Biological & pharmaceutical bulletin 27 ( 3 ) 422 - 5 2004.3

Language：English Publishing type：Research paper (scientific journal)

To investigate the structure-activity relationship of coumarins for the inhibitory activity on mushroom tyrosinase, the 50% inhibitory concentration (IC50 values) of 18 coumarins and four cinnamic acid derivatives were measured. Among these compounds, esculetin had the strongest inhibitory activity (IC50=43 microM) on mushroom tyrosinase. Introduction of a hydroxy group to the C6 and C7 positions of the coumarin ring and no substitution on the lactone ring played an important role in the expression of the strong inhibitory activity of esculetin. We performed further studies to estimate the in vitro inhibitory effects of esculetin on melanogenesis. Esculetin 5 microM significantly suppressed melanin production in murine B16 melanoma cells without affecting cell growth. Furthermore, the number of 3,4-dihydroxyphenylalanine (DOPA)-positive melanocytes in the split-epidermal sheets treated with 0.05% or 0.1% esculetin was significantly lower than that in the control. From these results, it is suggested that esculetin has inhibitory effects on tyrosinase activity in vitro. However, further detailed studies are necessary to understand the inhibitory mechanism of esculetin.

Reduction in photostability by the esterification of beta-cryptoxanthin. International journal

Shin Arita, Kojiro Otsuki, Ken-ichi Osaki, Yoshiyuki Murata, Yasuaki Shimoishi, Mikiro Tada

Bioscience, biotechnology, and biochemistry 68 ( 2 ) 451 - 3 2004.2

Language：English Publishing type：Research paper (scientific journal)

Liposomes, in which beta-carotene, beta-cryptoxanthin, zeaxanthin, beta-cryptoxanthin palmitate or beta-cryptoxanthin acetate had been embedded, were irradiated by UVA, and the rate of degradation of each carotenoid was measured. There was no significant difference in the degradation rate between beta-carotene, beta-cryptoxanthin and zeaxanthin. The degradation rates of beta-cryptoxanthin palmitate and beta-cryptoxanthin acetate were faster than that of beta-cryptoxanthin, and the degradation rate of beta-cryptoxanthin palmitate was faster than that of beta-cryptoxanthin acetate.

Plant Ion Channels as Potential Targets of Agro-Chemicals

OKUMA Eiji, MURATA Yoshiyuki

Journal of pesticide science 29 ( 4 ) 304 - 307 2004

Language：English Publisher：Pesticide Science Society of Japan

In the past 20 years, plant ion channels have been studied electrophysiologically, genetically and biochemically. However, much less study has been done on plant ion channels than animal and insect ion channels, especially in the field of pharmacology. Plant ion channels can serve as targets of agro-chemicals to control growth, stress tolerance and disease resistance, since they mediate physiological processes, like animal and insect ion channels. In this article, we review the current status of research on plant ion channels, in order to present guiding principles for designing new plant growth regulators and disease controlling agents.

DOI： 10.1584/jpestics.29.304

Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10877483

Effects of the fermentation product of herbs by lactic acid bacteria against phytopathogenic filamentous fungi and on the growth of host plants.

Shinsuke Kuwaki, Iichiro Ohhira, Masumi Takahata, Atsuko Hirota, Yoshiyuki Murata, Mikiro Tada

Journal of bioscience and bioengineering 98 ( 3 ) 187 - 92 2004

Language：English Publishing type：Research paper (scientific journal)

The fermentation product of herbs by lactic acid bacteria (FHL) was assayed for antifungal activities against Rosellinia necatrix, Helicobasidium mompa, Fusarium oxysporum, Pythium graminicola and Pyricularia oryzae. FHL completely inhibited the growth of R. necatrix, H. mompa, P. graminicola and P. oryzae, and reduced the growth of F. oxysporum by 35%. When the seeds of Medicago sativa L. (alfalfa), Asparagus officinalis L. (asparagus), Brassica campestris L. (komatsuna), Oryza sativa L. (rice), Spinacia oleracea L. (spinach), Festuca arundinacea Schreb. (tall fescue), and Lycopersicum esculentum Mill. (tomato) were put on plates containing 0.69 mg/ml FHL, their germination rates did not decrease. The root elongation of A. officinalis, B. campestris, O. sativa, and L. esculentum seedlings was suppressed on plates containing 6.92 mg/ml FHL, but the root elongation of M. sativa was not suppressed on the 6.92 mg/ml FHL plate. When FHL was diluted to less than 1.73 mg/ml, the diluted FHL solution did not suppress the germination of B. campestris seeds, but it suppressed the root elongation of B. campestris seedlings. An FHL concentration higher than 0.35 mg/ml hastened the growth of seedlings of B. campestris in the presence of a chemical fertilizer but delayed the growth of these seedlings in the absence of the chemical fertilizer, suggesting that inorganic elements could affect the efficiency of FHL.

Reduction of noise-stress-induced physiological damage by radices of Astragali and Rhodiolae: glycogen, lactic acid and cholesterol contents in liver of the rat. International journal

Bei-Wei Zhu, Yu-Mei Sun, Xia Yun, Song Han, Mei-Lan Piao, Yoshiyuki Murata, Mikiro Tada

Bioscience, biotechnology, and biochemistry 67 ( 9 ) 1930 - 6 2003.9

Language：English Publishing type：Research paper (scientific journal)

Noise is one of the factors that induces critical stress in animals. The contents of glycogen, lactic acid and cholesterol in the liver of noise-stressed rats were analyzed in order to investigate the alleviation of noise-stress-induced physiological damages by traditional medicine using Astragali and Rhodiolae radices. More than 95 dB noise ranging from 2 to 4 kHz reduced the contents of these compounds in the liver of rats not injected with the extract of Astragali or Rhodiolae, but did not change the contents in the liver of rats injected with the Astragali or Rhodiolae extract. These results show that noise induced stress in the rats via a decrease in contents of these compounds in the liver and that Astragali or Rhodiolae maintained the contents of these compounds in the liver of the noise-stressed rats. The results indicate that Astragali or Rhodiolae improved the ability for rats to resist noise stress.

Mushroom tyrosinase inhibitory activity of esculetin isolated from seeds of Euphorbia lathyris L. International journal

Yukimitsu Masamoto, Hideya Ando, Yoshiyuki Murata, Yasuaki Shimoishi, Mikiro Tada, Kyoya Takahata

Bioscience, biotechnology, and biochemistry 67 ( 3 ) 631 - 4 2003.3

Language：English Publishing type：Research paper (scientific journal)

A tyrosinase inhibitor was isolated from the seeds of Euphorbia lathyris L. by bioassay-guided fractionation and purification, using silica gel column chromatography. It was identified as esculetin by comparing its physical properties and spectral data with those of an authentic sample. The IC50 value of esculetin in the mushroom tyrosinase activity test was 43 microM. The kinetic study indicates that esculetin exhibited competitive inhibition against the oxidation of 3-(3,4-dihydroxyphenyl)-alanine by mushroom tyrosinase. The structure-activity relationships among five esculetin analogs suggest that hydroxyl groups at the C6 and C7 positions of the coumarin skeleton played an important role in the expression of tyrosinase inhibitory activity.

Quantitative analysis of allantoin in fresh tubers of Dioscorea opposita 'Tsukuneimo'

Akio Ninomiya, Yoshiyuki Murata, Mikiro Tada, Yasuaki Shimoishi

Journal of the Japanese Society for Horticultural Science 72 ( 4 ) 321 - 323 2003

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Society for Horticultural Science

Allantoin in fresh tuber of Dioscorea opposita 'Tsukuneimo' was quantitatively analyzed because the compound is thought to prevent inflammation and ulcers in humans as well as to play an important role for storage and translocation of nitrogen in higher plants. The content of ureide (allantoin and allantoic acid) in 'Tsukuneimo' was determined by the modified method of spectrophotometry with phenylhydrazine, whereas the content of allantoin was determined by HPLC. Analyses revealed that 'Tsukuneimo' tubers contained 2.6 mg·gFW-1 of allantoin, but leaves or stems had undetectable levels. D. opposita, 'Yamatoimo' and 'Nagaimo', and D. japonica 'Jinenjo' contained 2.3, 0.47 and 1.2 mg·gFW-1 of allantoin in the tuber, respectively, but negligible amount of allantoic acid in the tuber. Furthermore, Ipomoea batatas and Solanum tuberosum contained less than 0.1 mg·gFW-1 of allantoin and a negligible amount of allantoic acid. Colocasia antiquorum, 'Ishikawawase' and 'Kyouimo' had no detectable amounts of allantoin or allantoic acid.

DOI： 10.2503/jjshs.72.321

Convergence of calcium signaling pathways of pathogenic elicitors and abscisic acid in Arabidopsis guard cells Reviewed International journal

B Klusener, JJ Young, Y Murata, GJ Allen, IC Mori, Hugouvieux, V, JI Schroeder

PLANT PHYSIOLOGY 130 ( 4 ) 2152 - 2163 2002.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER SOC PLANT BIOLOGISTS

A variety of stimuli, such as abscisic acid (ABA), reactive oxygen species (ROS), and elicitors of plant defense reactions, have been shown to induce stomatal closure. Our study addresses commonalities in the signaling pathways that these stimuli trigger. A recent report showed that both ABA and ROS stimulate an NADPH-dependent, hyperpolarization-activated Ca2+ influx current in Arabidopsis guard cells termed "I-Ca" (Z.M. Pei, Y. Murata, G. Benning, S. Thomine, B. Klusener, G.J. Allen, E. Grill, J.I. Schroeder, Nature [2002] 406: 731-734). We found that yeast (Saccharomyces cerevisiae) elicitor and chitosan, both elicitors of plant defense responses, also activate this current and activation requires cytosolic NAD(P)H. These elicitors also induced elevations in the concentration of free cytosolic calcium ([Ca2+](cyt)) and stomatal closure in guard cells. ABA and ROS elicited [Ca2+](cyt), oscillations in guard cells only when extracellular Ca2+ was present. In a 5 mM KCl extracellular buffer, 45% of guard cells exhibited spontaneous [Ca2+](cyt) oscillations that differed in their kinetic properties from ABA-induced Ca2+ increases. These spontaneous [Ca2+](cyt) oscillations also required the availability of extracellular Ca2+ and depended on the extracellular potassium concentration. Interestingly, when ABA was applied to spontaneously oscillating cells, ABA caused cessation of [Ca2+](cyt), elevations in 62 of 101 cells, revealing a new mode of ABA signaling. These data show that fungal elicitors activate a shared branch with ABA in the stress signal transduction pathway in guard cells that activates plasma membrane I-Ca channels and support a requirement for extracellular Ca2+ for elicitor and ABA signaling, as well as for cellular [Ca2+](cyt) oscillation maintenance.

DOI： 10.1104/pp.012187

Localization, ion channel regulation, and genetic interactions during abscisic acid signaling of the nuclear mRNA cap-binding protein, ABH1. International journal

Véronique Hugouvieux, Yoshiyuki Murata, Jared J Young, June M Kwak, Daniel Z Mackesy, Julian I Schroeder

Plant physiology 130 ( 3 ) 1276 - 87 2002.11

Language：English Publishing type：Research paper (scientific journal)

Abscisic acid (ABA) regulates developmental processes and abiotic stress responses in plants. We recently characterized a new Arabidopsis mutant, abh1, which shows ABA-hypersensitive regulation of seed germination, stomatal closing, and cytosolic calcium increases in guard cells (V. Hugouvieux, J.M. Kwak, J.I. Schroeder [2001] Cell 106: 477-487). ABH1 encodes the large subunit of a dimeric Arabidopsis mRNA cap-binding complex and in expression profiling experiments was shown to affect mRNA levels of a subset of genes. Here, we show that the dimeric ABH1 and AtCBP20 subunits are ubiquitously expressed. Whole-plant growth phenotypes of abh1 are described and properties of ABH1 in guard cells are further analyzed. Complemented abh1 lines expressing a green fluorescent protein-ABH1 fusion protein demonstrate that ABH1 mainly localizes in guard cell nuclei. Stomatal apertures were smaller in abh1 compared with wild type (WT) when plants were grown at 40% humidity, and similar at 95% humidity. Correlated with stomatal apertures from plants grown at 40% humidity, slow anion channel currents were enhanced and inward potassium channel currents were decreased in abh1 guard cells compared with WT. Gas exchange measurements showed similar primary humidity responses in abh1 and WT, which together with results from abh1/abi1-1 double-mutant analyses suggest that abh1 shows enhanced sensitivity to endogenous ABA. Double-mutant analyses of the ABA-hypersensitive signaling mutants, era1-2 and abh1, showed complex genetic interactions, suggesting that ABH1 and ERA1 do not modulate the same negative regulator in ABA signaling. Mutations in the RNA-binding protein sad1 showed hypersensitive ABA-induced stomatal closing, whereas hyl1 did not affect this response. These data provide evidence for the model that the mRNA-processing proteins ABH1 and SAD1 function as negative regulators in guard cell ABA signaling.

Disruption of a Guard Cell–Expressed Protein Phosphatase 2A Regulatory Subunit, RCN1 , Confers Abscisic Acid Insensitivity in Arabidopsis Reviewed International journal

June M. Kwak, Ji-Hye Moon, Yoshiyuki Murata, Kazuyuki Kuchitsu, Nathalie Leonhardt, Alison DeLong, Julian I. Schroeder

The Plant Cell 14 ( 11 ) 2849 - 2861 2002.10

Language：English Publishing type：Research paper (scientific journal) Publisher：American Society of Plant Biologists ({ASPB})

Pharmacological studies have led to a model in which the phytohormone abscisic acid (ABA) may be positively transduced via protein phosphatases of the type 1 (PP1) or type 2A (PP2A) families. However, pharmacological evidence also exists that PP1s or PP2As may function as negative regulators of ABA signaling. Furthermore, recessive disruption mutants in protein phosphatases that function in ABA signal transduction have not yet been identified. A guard cell-expressed PP2A gene, RCN1, which had been characterized previously as a molecular component affecting auxin transport and gravity response, was isolated. A T-DNA disruption mutation in RCN1 confers recessive ABA insensitivity to Arabidopsis. The rcn1 mutation impairs ABA-induced stomatal closing and ABA activation of slow anion channels. Calcium imaging analyses show a reduced sensitivity of ABA-induced cytosolic calcium increases in rcn1, whereas mechanisms downstream of cytosolic calcium increases show wild-type responses, suggesting that RCN1 functions in ABA signal transduction upstream of cytosolic Ca(2+) increases. Furthermore, rcn1 shows ABA insensitivity in ABA inhibition of seed germination and ABA-induced gene expression. The PP1 and PP2A inhibitor okadaic acid phenocopies the rcn1 phenotype in wild-type plants both in ABA-induced cytosolic calcium increases and in seed germination, and the wild-type RCN1 genomic DNA complements rcn1 phenotypes. These data show that RCN1 functions as a general positive transducer of early ABA signaling.

DOI： 10.1105/tpc.003335

Hypersensitivity of abscisic acid-induced cytosolic calcium increases in the Arabidopsis farnesyltransferase mutant era1-2. International journal

Gethyn J Allen, Yoshiyuki Murata, Sarah P Chu, Majse Nafisi, Julian I Schroeder

The Plant cell 14 ( 7 ) 1649 - 62 2002.7

Language：English Publishing type：Research paper (scientific journal)

Cytosolic calcium increases were analyzed in guard cells of the Arabidopsis farnesyltransferase deletion mutant era1-2 (enhanced response to abscisic acid). At low abscisic acid (ABA) concentrations (0.1 microM), increases of guard cell cytosolic calcium and stomatal closure were activated to a greater extent in the era1-2 mutant compared with the wild type. Patch clamping of era1-2 guard cells showed enhanced ABA sensitivity of plasma membrane calcium channel currents. These data indicate that the ERA1 farnesyltransferase targets a negative regulator of ABA signaling that acts between the points of ABA perception and the activation of plasma membrane calcium influx channels. Experimental increases of cytosolic calcium showed that the activation of S-type anion currents downstream of cytosolic calcium and extracellular calcium-induced stomatal closure were unaffected in era1-2, further supporting the positioning of era1-2 upstream of cytosolic calcium in the guard cell ABA signaling cascade. Moreover, the suppression of ABA-induced calcium increases in guard cells by the dominant protein phosphatase 2C mutant abi2-1 was rescued partially in era1-2 abi2-1 double mutant guard cells, further reinforcing the notion that ERA1 functions upstream of cytosolic calcium and indicating the genetic interaction of these two mutations upstream of ABA-induced calcium increases.

Abscisic acid activation of plasma membrane Ca2+ channels in guard cells requires cytosolic NAD(P)H and is differentially disrupted upstream and downstream of reactive oxygen species production in abi1-1 and abi2-1 protein phosphatase 2C mutants (vol 13, pg 2513, 2001) Reviewed

Y Murata, ZM Pei, IC Mori, J Schroeder

PLANT CELL 14 ( 1 ) 287 - 287 2002.1

Antifungal activity of the fermentation product of herbs by lactic acid bacteria against tinea.

Shinsuke Kuwaki, Iichiro Ohhira, Masumi Takahata, Yoshiyuki Murata, Mikiro Tada

Journal of bioscience and bioengineering 94 ( 5 ) 401 - 5 2002

Language：English Publishing type：Research paper (scientific journal)

The fermentation product of herbs by lactic acid bacteria (FHL), in which Enterococcus faecalis TH10 predominated, was assayed for antifungal activity against tinea. The antifungal activity of FHL was as high as that of a synthetic fungicide. Autoclaving FHL did not reduce its antifungal activity, whereas neutralizing it did. The results suggested that nonproteinaceous compounds or organic acids in FHL could inhibit the growth of the dermatophyte tinea under low-pH conditions, and that malonic acid and acetic acid could have especially high antifungal activity against tinea.

Exogenous Proline Mitigates the Inhibition of Growth of Nicotiana tabacum Cultured Cells under Saline Conditions

OKUMA Eiji, SOEDA Kenji, TADA Mikiro, MURATA Yoshiyuki

Soil Science and Plant Nutrition 46 ( 1 ) 257 - 263 2000.3

Language：English Publisher：Japanese Society of Soil Science and Plant Nutrition

The addition of exogenous proline (10 mM) to Na100-saline culture medium, modified LS medium (Linsmaier and Skoog 1965: Physiol. Plant., 18, 100-127) with 100 mM NaCl promoted the growth of tobacco (Nicotiana tabacum L., cv. Bright Yellow-2) suspension cells unadapted to salt stress without maintaining a high ratio of K^+ to Na^+ ions under salinity conditions. The addition of exogenous glutamic acid or alanine were not comparable to that of exogenous proline. The proline contents of the NaCl-unadapted cells became much higher when the cells were grown in Na100-saline culture medium with 10 mM proline than when the cells were cultured without proline. The accumulation of K^+, Na^+, and counter ions was sufficient to compensate for the increase of the water potential of the cells caused by salinity. These results suggest that exogenous proline does not act as a nitrogen store and that proline may act as a protectant for enzymes and membranes against salt inactivation rather than as a compatible solute in tobacco suspension cells.

Analysis of fatty acids and sterols of plasma membrane and tonoplast isolated from salt-stress adaptation of Tobacco cultured cells in suspension :

HINO Tomoyuki, TANAKA Tadayuki, OKUMA Eiji, MURATA Yoshiyuki, TADA Mikiro

Plant and cell physiology 41 s22 2000

Sterilization of proteinaceous food additives by irradiation : Temperature dependent changes in intensity of ESR signals generated by electron beam irradiation Reviewed

SAKAUE Kazushi, HIGASHIMURA Yutaka, HAYASHI Toru, TODORIKI Setsuko, MURATA Yoshiyuki, TADA Mikiro

FOOD IRRADIATION, JAPAN 34 ( 1/2 ) 30 - 36 1999.9

Language：Japanese Publisher：JAPANESE RESEARCH ASSOCIATION FOR FOOD IRRADIATION

Thaumatin, egg white and soybean protein were selected as samples of proteinous food additives, and changes in the intensity of signals appearing in them after they had been irradiated with electron beams were measured by ESR. It was found by such measurement that the positions of signals of thaumatin and soy proteins are nearly the same. Changes in the intensity of radicals in thaumatin calculated on the basis of the coefficients of the respective approximations obtained by using thaumatin which had been irradiated and then stored at 4°C, 25°C, 37°C and 60°C showed that there is a temperature range to determine the remaining of such radicals (inner: 19.7°C, outer: 15.23°C) and that such radicals tend to decrease straight line-wise. It was confirmed that the intensity of signals in the protein powder such thaumatin and soy protein would not be affected at the storage condition below 15°C.

DOI： 10.5986/jrafi.34.30

Other Link： https://jlc.jst.go.jp/DN/JALC/00063347975?from=CiNii

Sterilization of Proteinaceous Food Additives by irradiation : Effect of water sorption isotherm and gel strength of whey protein concentrate, collagen and egg white protein by electron beam irradiation

Sakaue Kazushi, Higashimura Yutaka, Murata Yoshiyuki, Hayashi Toru, Todoroki Setsuko, Tada Mikiro

Japanese Journal of Food Chemistry and Safety 6 ( 1 ) 16 - 23 1999

Language：Japanese Publisher：Japanese Society of Food Chemistry

In order to get prepared for the future practical use of irradiation for the purpose of controlling the microorganisms existing in proteinaceous food additives, we conducted studies on their water sorption isotherm and molecular weight distribution as their functional properties for gelation by irradiating three kind of them with electronic beams up to 25 kGy. The results of such studies were as follows: (1) In the case of a whey protein concentrate, only a few changes were observed in its water absorption volume and molecular weight distribution, and almost no change was observed in its gel strength; (2) In the case of a collagen, a decreasing tendency was observed in its water absorption volume, and a big change was observed in its molecular weight distribution, indicating that both polymerization and decomposition reaction were occurring simultaneously. In terms of its gel strength, however, no remarkable change was observed when irradiation was conducted below 20 kGy, while a weakening tendency was observed when irradiation was conducted at a high absorption dose such as at 20 kGy or above; (3) In the case of an egg white protein, slight increases were observed both in its water absorption volume and molecular weight distribution respectively, and changes in its molecular weight distribution indicated the occurrence of polymerization at a medium absorption dose and the occurrence of decomposition reaction at a high absorption dose; and (4) It is said that irradiation at 5 kGy is sufficient for the sterilization of proteinaceous food additives to kill the microorganisms existing therein, and in fact, an international absorption-dose guideline for the irradiation of foodstuffs also recommends irradiation at less than 10 kGy. It was confirmed by us that the function of gelation required of proteinaceous food additives as one of their main functional properties would not be affected by irradiation at such medium absorption-dose levels.

DOI： 10.18891/jjfcs.6.1_16

Arabidopsis abi1-1 and abi2-1 phosphatase mutations reduce abscisic acid-induced cytoplasmic calcium rises in guard cells

Gethyn J. Allen, Kazuyuki Kuchitsu, Sarah P. Chu, Yoshiyuki Murata, Julian I. Schroeder

Plant Cell 11 ( 9 ) 1785 - 1798 1999

Language：English Publishing type：Research paper (scientific journal) Publisher：American Society of Plant Biologists

Elevations in cytoplasmic calcium ([Ca2+](cyt)) are an important component of early abscisic acid (ABA) signal transduction. To determine whether defined mutations in ABA signal transduction affect [Ca2+](cyt) signaling, the Ca2+-sensitive fluorescent dye fura 2 was loaded into the cytoplasm of Arabidopsis guard cells. Oscillations in [Ca2+](cyt) could be induced when the external calcium concentration was increased, showing viable Ca2+ homeostasis in these dye-loaded cells. ABA-induced [Ca2+](cyt) elevations in wild-type stomata were either transient or sustained, with a mean increase of ~300 nM. Interestingly, ABA-induced [Ca2+](cyt) increases were significantly reduced but not abolished in guard cells of the ABA-insensitive protein phosphatase mutants abi1 and abi2. Plasma membrane slow anion currents were activated in wild-type, abi1, and abi2 guard cell protoplasts by increasing [Ca2+](cyt), demonstrating that the impairment in ABA activation of anion currents in the abi1 and abi2 mutants was bypassed by increasing [Ca2+](cyt). Furthermore, increases in external calcium alone (which elevate [Ca2+](cyt)) resulted in stomatal closing to the same extent in the abi1 and abi2 mutants as in the wild type. Conversely, stomatal opening assays indicated different interactions of abi1 and abi2, with Ca2+-dependent signal transduction pathways controlling stomatal closing versus stomatal opening. Together, [Ca2+](cyt) recordings, anion current activation, and stomatal closing assays demonstrate that the abi1 and abi2 mutations impair early ABA signaling events in guard cells upstream or close to ABA-induced [Ca2+](cyt) elevations. These results further demonstrate that the mutations can be bypassed during anion channel activation and stomatal closing by experimental elevation of [Ca2+](cyt).

DOI： 10.1105/tpc.11.9.1785

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