KINDAI UNIVERSITY


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ISHIMARU Megumi

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FacultyDepartment of Science and Technology on Food Safety / Graduate School of Biology-Oriented Science and Technology
PositionProfessor
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Commentator Guidehttps://www.kindai.ac.jp/meikan/153-ishimaru-megumi.html
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Last Updated :2020/09/30

Education and Career

Education

  •  - 1999 , Osaka Prefecture University

Academic & Professional Experience

  •   2010 ,  - 2012 , Faculty of Biology-Oriented Science and Technology, Kindai University
  •   2000 04 ,  - 2010 03 , Graduate School of Life and Environmental Sciences, Osaka Prefecture University

Research Activities

Research Areas

  • Environmental science/Agricultural science, Horticulture

Published Papers

  • Structural and functional analysis of tomato-galactosidase4: insight into the substrate specificity of the fruit softening-related enzyme, Masahiro Eda, Takashi Matsumoto, Megumi Ishimaru, Toshiji Tada, PLANT JOURNAL, PLANT JOURNAL, 86(4), 300 - 307, May 2016 , Refereed
    Summary:Plant -galactosidases hydrolyze cell wall -(1,4)-galactans to play important roles in cell wall expansion and degradation, and turnover of signaling molecules, during ripening. Tomato -galactosidase4 (TBG4) is an enzyme responsible for fruit softening through the degradation of -(1,4)-galactan in the pericarp cell wall. TBG4 is the only enzyme among TBGs1-7 that belongs to the -galactosidase/exo--(1,4)-galactanase subfamily. The enzyme can hydrolyze a wide range of plant-derived (1,4)- or 4-linked polysaccharides, and shows a strong ability to attack -(1,4)-galactan. To gain structural insight into its substrate specificity, we determined crystal structures of TBG4 and its complex with -d-galactose. TBG4 comprises a catalytic TIM barrel domain followed by three -sandwich domains. Three aromatic residues in the catalytic site that are thought to be important for substrate specificity are conserved in GH35 -galactosidases derived from bacteria, fungi and animals; however, the crystal structures of TBG4 revealed that the enzyme has a valine residue (V548) replacing one of the conserved aromatic residues. The V548W mutant of TBG4 showed a roughly sixfold increase in activity towards -(1,6)-galactobiose, and similar to 0.6-fold activity towards -(1,4)-galactobiose, compared with wild-type TBG4. Amino acid residues corresponding to V548 of TBG4 thus appear to determine the substrate specificities of plant -galactosidases towards -1,4 and -1,6 linkages. Significance Statement Tomato -galactosidases (TBG1-TBG7) in the glycosyl hydrolase 35 (GH35) family are thought to play important roles during fruit development and maturation. Here we report the crystal structure of TBG4 in complex with its substrate.
  • Expression, purification, crystallization and preliminary X-ray crystallographic analysis of tomato beta-galactosidase 4, Masahiro Eda, Megumi Ishimaru, Toshiji Tada, ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS, ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS, 71(Pt 2), 153 - 156, Feb. 2015 , Refereed
    Summary:Plant beta-galactosidases play important roles in carbohydrate-reserve mobilization, cell-wall expansion and degradation, and turnover of signalling molecules during ripening. Tomato beta-galactosidase 4 (TBG4) not only has beta-galactosidase activity but also has exo-beta-(1,4)-galactanase activity, and prefers beta-(1,4)-galactans longer than pentamers as its substrates; most other beta-galactosidases only have the former activity. Recombinant TBG4 protein expressed in the yeast Pichia pastoris was crystallized by the sitting-drop vapour-diffusion method using PEG 10 000 as a precipitant. The crystals belonged to the orthorhombic space group P2(1)2(1)2(1), with unit-parameters a = 92.82, b = 96.30, c = 159.26 angstrom, and diffracted to 1.65 angstrom resolution. Calculation of the Matthews coefficient suggested the presence of two monomers per asymmetric unit (V-M = 2.2 angstrom(3) Da(-1)), with a solvent content of 45%.
  • Enzymatic activity and substrate specificity of the recombinant tomato beta-galactosidase 1, Masahiro Eda, Megumi Ishimaru, Toshiji Tada, Tatsuji Sakamoto, Toshihisa Kotake, Yoichi Tsumuraya, Andrew J. Mort, Kenneth C. Gross, JOURNAL OF PLANT PHYSIOLOGY, JOURNAL OF PLANT PHYSIOLOGY, 171(16), 1454 - 1460, Oct. 2014 , Refereed
    Summary:The open reading frame of tomato beta-galactosidase 1 was expressed in yeast, and the enzymatic properties and substrate specificity were investigated. The enzyme had peak activity at pH 5.0 and 40-50 degrees C. TBG1 was active on beta-(1,3)- and beta-(1,6)-galactobiose and lactose. TBG1 released galactose from lupin galactan, tomato fruit alkali soluble pectin, arabinogalactan, gum arabic and methyl beta-(1,6)-galactohexaoside, but not from labeled beta-(1,4)-galactoheptaose. TBG1 was assessed for its ability to degrade three galactosyl-containing cell wall fractions purified from different development and ripening stages of tomato fruit. TBG1 released galactose from all of the fractions from all of the stages tested. TBG1 activity was highest on the hemicellulose fraction at the 10 and 20 d after pollination stage. This result is not correlated the with TBG1 expression pattern. TBG1 might act on a small but specific set of polysaccharide containing galactose. (C) 2014 Elsevier GmbH. All rights reserved.
  • Characterization of an exo-beta-1,3-d-galactanase from Sphingomonas sp. 24T and its application to structural analysis of larch wood arabinogalactan, Tatsuji Sakamoto, Hiromasa Tanaka, Yuichi Nishimura, Megumi Ishimaru, Naoya Kasai, APPLIED MICROBIOLOGY AND BIOTECHNOLOGY, APPLIED MICROBIOLOGY AND BIOTECHNOLOGY, 90(5), 1701 - 1710, Jun. 2011 , Refereed
    Summary:A type II arabinogalactan-degrading enzyme, termed Exo-1,3-Gal, was purified to homogeneity from the culture filtrate of Sphingomonas sp. 24T. It has an apparent molecular mass of 48 kDa by SDS-PAGE. Exo-1,3-Gal was stable from pH 3 to 10 and at temperatures up to 40 A degrees C. The optimum pH and temperature for enzyme activity were pH 6 to 7 and 50 A degrees C, respectively. Galactose was released from beta-1,3-d-galactan and beta-1,3-d-galactooligosaccharides by the action of Exo-1,3-Gal, indicating that the enzyme was an exo-beta-1,3-d-galactanase. Analysis of the reaction products of beta-1,3-galactotriose by high-performance anion-exchange chromatography revealed that the enzyme hydrolyzed the substrate in a non-processive mode. Exo-1,3-Gal bypassed the branching points of beta-1,3-galactan backbones in larch wood arabinogalactan (LWAG) to produce mainly galactose, beta-1,6-galactobiose, and unidentified oligosaccharides 1 and 2 with the molar ratios of 7:19:62:12. Oligosaccharides 1 and 2 were enzymatically determined to be beta-1,6-galactotriose and beta-1,6-galactotriose substituted with a single arabinofuranose residue, respectively. The ratio of side chains enzymatically released from LWAG was in good agreement with the postulated structure of the polysaccharide previously determined by chemical methods.
  • Characterization of an exo-beta-1,3-d-galactanase from Sphingomonas sp. 24T and its application to structural analysis of larch wood arabinogalactan, Tatsuji Sakamoto, Hiromasa Tanaka, Yuichi Nishimura, Megumi Ishimaru, Naoya Kasai, APPLIED MICROBIOLOGY AND BIOTECHNOLOGY, APPLIED MICROBIOLOGY AND BIOTECHNOLOGY, 90(5), 1701 - 1710, Jun. 2011 , Refereed
    Summary:A type II arabinogalactan-degrading enzyme, termed Exo-1,3-Gal, was purified to homogeneity from the culture filtrate of Sphingomonas sp. 24T. It has an apparent molecular mass of 48 kDa by SDS-PAGE. Exo-1,3-Gal was stable from pH 3 to 10 and at temperatures up to 40 A degrees C. The optimum pH and temperature for enzyme activity were pH 6 to 7 and 50 A degrees C, respectively. Galactose was released from beta-1,3-d-galactan and beta-1,3-d-galactooligosaccharides by the action of Exo-1,3-Gal, indicating that the enzyme was an exo-beta-1,3-d-galactanase. Analysis of the reaction products of beta-1,3-galactotriose by high-performance anion-exchange chromatography revealed that the enzyme hydrolyzed the substrate in a non-processive mode. Exo-1,3-Gal bypassed the branching points of beta-1,3-galactan backbones in larch wood arabinogalactan (LWAG) to produce mainly galactose, beta-1,6-galactobiose, and unidentified oligosaccharides 1 and 2 with the molar ratios of 7:19:62:12. Oligosaccharides 1 and 2 were enzymatically determined to be beta-1,6-galactotriose and beta-1,6-galactotriose substituted with a single arabinofuranose residue, respectively. The ratio of side chains enzymatically released from LWAG was in good agreement with the postulated structure of the polysaccharide previously determined by chemical methods.
  • Changes in inner contents of ‘Kyoho’ grape berry during the growth and ripening period., T. Ban, A. Nakatsuka, K. Akaura, S. Matsumoto, M. Ishimaru, H. Itamura, Applied Horticulture, Applied Horticulture, 12, 93 - 96, Dec. 2010 , Refereed
  • Pathway of acetate ester formation in banana fruit pulp., Wendakoon S.K, Ueda Y, Imahori Y, Ishimaru M, Journal of Japanese Association of Food Preservation Science, Journal of Japanese Association of Food Preservation Science, 30, 17 - 21, Oct. 2004 , Refereed
  • Aliphatic and aromatic alcohol acyltranferase from melon (Cucumis melo L. cv. Prince Melon)., Khanom M, Ueda Y, Imahori Y, Ishimaru M, Noichinda S, Applied Biological Science, Applied Biological Science, 7, 71 - 83, Apr. 2003 , Refereed
  • HPLCによるブルーベリー果実およびジャム中のアントシアニンの分析., 29(3), 153 - 157, Feb. 2003 , Refereed
  • Relationship between volatiles and other factors indicating quality of melon (Cucumis melo cv. Prince Melon) during fruit development and storage., Khanom M, Ueda Y, Ishimaru M, Scientific Report of Graduate School of Agriculture & Biological Sciences, Osaka Prefecture University, Scientific Report of Graduate School of Agriculture & Biological Sciences, Osaka Prefecture University, 55, 7 - 14, Jan. 2003 , Refereed
  • Effects of on-tree removal of astringency by ethanol treatment on β-D-galacosidase gene expression of Japanese persimmon Tonewase fruit., Ishimaru M, Kobayashi S, Imahori Y, Ueda Y, Applied Biological Science, Applied Biological Science, 4, 77 - 83, Oct. 1998 , Refereed
  • Microbiological and Visual Quality of Enzymatically Peeled Baby Persimmons Stored in High CO2 Controlled Atmospheres, H. Izumi, Y. Murakami, M. Ishimaru, Y. Ozaki, XI INTERNATIONAL CONTROLLED AND MODIFIED ATMOSPHERE RESEARCH CONFERENCE, XI INTERNATIONAL CONTROLLED AND MODIFIED ATMOSPHERE RESEARCH CONFERENCE, 1071, 203 - 209, 2015 , Refereed
    Summary:Freshly peeled "baby persimmons", 3-4 cm in diameter and 20-25 g in weight, were prepared by enzymatic peeling of 'Totsutanenashi' cherry persimmon fruit (Diospyros kaki Thunb.), which is a bud mutation and miniature of the full size 'Hiratanenashi' persimmon. The microbiological and visual quality of enzymatically peeled baby persimmons as a fresh-cut fruit was evaluated during storage in air or high CO2 atmospheres (10, 15 and 20%) at 10 degrees C. The flesh of intact baby persimmon fruit showed counts of 2.6 log CFU/g for mesophilic aerobic bacteria and a non-detectable level for coliform groups and fungi. A hot water dipping treatment in the enzymatic peeling process reduced both the counts of mesophiles to levels below the lower limit of detection (2.4 log CFU/g) and the diversity of bacterial flora. Coliforms and fungi remained undetectable throughout the enzymatic peeling process. During storage in air, counts of mesophiles, coliforms, lactic acid bacteria, and fungi of baby persimmons increased to 4-5.5 log CFU/g by day 6, while high CO2 atmospheres reduced the microbial growth, with the greatest reduction observed in 15 or 20% CO2. Diversity of the microflora also decreased in 20% CO2 atmosphere as compared to air on day 6. High CO2 atmospheres inhibited the development of brown discoloration in baby persimmons by day 4, but all samples developed browning to an unmarketable level by day 6. These results indicate that high CO2 atmospheres of 15 to 20% are desirable for enzyme-peeled baby persimmons to extend the shelf life when stored at 10 degrees C.
  • Peculiarities and applications of galactanolytic enzymes that act on type I and II arabinogalactans, Tatsuji Sakamoto, Megumi Ishimaru, APPLIED MICROBIOLOGY AND BIOTECHNOLOGY, APPLIED MICROBIOLOGY AND BIOTECHNOLOGY, 97(12), 5201 - 5213, Jun. 2013 , Refereed
    Summary:Arabinogalactans (AGs) are branched galactans to which arabinose residues are bound as side chains and are widely distributed in plant cell walls. They can be grouped into two types based on the structures of their backbones. Type I AGs have beta-1,4-galactan backbones and are often covalently linked to the rhamnogalacturonan-I region of pectins. Type II AGs have beta-1,3-galactan backbones and are often covalently linked to proteins. The main enzymes involved in the degradation of AGs are endo-beta-galactanases, exo-beta-galactanases, and beta-galactosidases, although other enzymes such as alpha-l-arabinofuranosidases, beta-l-arabinopyranosidases, and beta-d-glucuronidases are required to remove the side chains for efficient degradation of the polysaccharides. Galactanolytic enzymes have a wide variety of potential uses, including the bioconversion of AGs to fermentable sugars for production of commodity chemicals like ethanol, biobleaching of cellulose pulp, modulation of pectin properties, improving animal feed, and determining the chemical structure of AGs. This review summarizes our current knowledge about the biochemical properties and potential applications of AG-degrading enzymes.
  • Enzymatic activity and substrate specificity of recombinant tomato beta-galactosidases 4 and 5, Megumi Ishimaru, David L. Smith, Andrew J. Mort, Kenneth C. Gross, PLANTA, PLANTA, 229(2), 447 - 456, Jan. 2009 , Refereed
    Summary:The open reading frames of tomato beta-galactosidase (TBG) 4 and 5 cDNAs were expressed in yeast, and the enzymes properties and substrate specificities were investigated. The two enzymes had peak activities between pH 4-4.5 and 37-45A degrees C. TBG4 specifically hydrolyzed beta-(1 -> 4) and 4-linked galactooligosaccharides. TBG5 had a strong preference to hydrolyze beta-(1 -> 3) and beta-(1 -> 6)-linked galactooligosaccharides. Exo-beta-galactanase activity of the TBG enzymes was measured by determining the release of galactosyl residues from native tomato cell wall fractions throughout fruit development and ripening. Both TBGs released galactose from all of the fractions and stages tested. TBG4 activity was highest using chelator soluble pectin and alkali soluble pectin at the turning stage of ripening. Using aminopyrene trisulfonate labeled substrates, TBG4 was the only enzyme with strong exo-beta-(1 -> 4)-galactanase activity on 5 mer or greater galactans. TBG4 and TBG5 were both able to degrade galactosylated rhamnogalacturonan. Neither enzyme was able to degrade galactosylated xyloglucan.
  • An anthocyanin regulator from grapes, VlmybA1-2, produces reddish-purple plants, Yoshiko Koshita, Shozo Kobayashi, Megumi Ishimaru, Yoshio Funamoto, Mikio Shiraishi, Akifumi Azuma, Hiroshi Yakushiji, Masayoshi Nakayama, JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE, JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE, 77(1), 33 - 37, Jan. 2008
    Summary:A cDNA, VlmybA1-2, for an anthocyanin regulatory gene of grape was constructed under the control of the cauliflower mosaic virus (CaMV) 35SRNA promoter and introduced into leaf disks and petioles of kiwifruit (Actinidia deliciosa) plants by Agrobacterium-mediated gene transfer. When the tissues were cultured on selection medium, red cells visible to the naked eye formed at the cut ends of the segments after approximately 2 weeks. The cells developed into calluses, adventitious buds, and reddish-purple plantlets after 2, 3, and 6 months of culture, respectively. The pigment produced in the leaves of the transformed plants was determined to be cyanidin 3-O-(2-O-beta-xylosyl)-beta-glucoside (cyanidin 3-O-sambubioside). As VlmybA1-2 can also produce red cells in tomato and eggplant, it may be useful as a visible marker to confirm efficient transformation in dicots.
  • Expression of three expansin genes during development and maturation of Kyoho grape berries, Megumi Ishimaru, David L. Smith, Kenneth C. Gross, Shozo Kobayashi, JOURNAL OF PLANT PHYSIOLOGY, JOURNAL OF PLANT PHYSIOLOGY, 164(12), 1675 - 1682, Dec. 2007 , Refereed
    Summary:Expansins are cell-wall-localized proteins that induce Loosening of isolated plant cell walls in vitro in a pH-dependent manner, but exhibit no detectable hydrolase or transglycosylase activity. Three putative expansin cDNAs, Vlexp1, Vlexp2, and Vlexp3 were isolated from a cDNA library made from mature berries of the Kyoho grape. Expression profiles of the 3 genes were analyzed throughout berry development. Accumulation of the Vlexp3 transcript was closely correlated with berry softening, and expression of this gene was detected before veraison and markedly increased at veraison (onset of berry softening). Expression of Vlexp3 was berry-specific. Vlexp1 and Vlexp2 mRNA accumulation began during the expansion stage of berry development and expression increased for both genes during ripening. Vlexp1 and Vlexp2 mRNA was detected in Leaf, tendril and flower tissues and Vlexp2 mRNA was additionally detected in root and seed tissues. These findings suggest that the three expansin genes are associated with cell division or expansion and berry ripening. Vlexp3, in particular, is most likely to play a rote in grape berry softening at veraison. (C) 2006 Elsevier GmbH. All rights reserved.
  • Physiological responses and quality attributes of Chinese chive leaves exposed to CO2-enriched atmospheres, Yoshihiro Imahori, Yoshitaka Suzuki, Minako Kawagishi, Megumi Ishimaru, Yoshinori Ueda, Kazuo Chachin, POSTHARVEST BIOLOGY AND TECHNOLOGY, POSTHARVEST BIOLOGY AND TECHNOLOGY, 46(2), 160 - 166, Nov. 2007
    Summary:Harvested leaves of Chinese chives were stored in air + 10, 20 or 30% CO2, or air for 7 days at 20 degrees C to determine the effects of CO(2-)enriched atmospheres on their physiology and quality. Leaf yellowing was visible at day 5 in air, whereas CO, enrichment delayed yellowing and retarded chlorophyll and protein degradation that accompanied leaf senescence. At 30% CO2, undesirable off-odors were induced, presumably due to accumulation of ethanol in the tissue. The ethanol contents did not change during storage in leaves exposed to 10 or 20% CO2, or air, while the content in leaves exposed to 30% CO2 significantly increased. However, CO2 enrichment did not significantly influence acetaldehyde concentrations for the leaves. Alcohol dehydrogenase (ADH) activity increased in leaves exposed to 10 or 20% CO2, while its activity in leaves exposed to 30% CO2, was slightly higher than that of the control. Succinate dehydrogenase (SDH) activity greatly decreased in leaves exposed to 30% CO2, while its activity in leaves exposed to 10 or 20% CO2 only decreased slightly. The content of pyruvate increased in leaves exposed to 30% CO2, while its concentration in leaves exposed to 10 or 20% CO2, was slightly higher than that of the controls. Thus, our results indicate that it would be necessary to keep Chinese chives at 20 degrees C because of a lack of refrigeration in the distribution system, or in a modified atmosphere package designed to develop an optimum atmosphere during retail display, and suggest a potential for using CO2-enriched atmospheres at higher temperatures to help maintain quality. (C) 2007 Elsevier B.V. All rights reserved.
  • Effects of short-term exposure to low oxygen atmospheres on phsyiological responses of sweetpotato roots, Yoshihiro Imahori, Izumi Kishioka, Kazuko Uemura, Eiichi Makita, Hitomi Fujiwara, Yuka Nishiyama, Megumi Ishimaru, Yoshinori Ueda, Kazuo Chachin, JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE, JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE, 76(3), 258 - 265, Jul. 2007
    Summary:Sweetpotato roots were stored under a continuous flow of 0% or 1% O-2 (balance N-2) or air for 7 days at 20 degrees C to study the effects of short-term exposure to low OZ on their physiological responses and quality. During the course of the experiment, no visible signs of injury or decay were observed. However, low OZ treatments increased the soluble solid content and weak off-odors were detected by olfactory evaluation in roots stored at 0%O-2. The intensity of off-odors increased as the concentrations of acetaldehyde and ethanol increased in roots during storage. Ethanol concentrations were higher than those of acetaldehyde, which remained low during storage in 1% O-2 and air, but increased greatly in roots stored at 0% O-2. Pyruvate decarboxylase (PDC) activities in roots exposed to 0% or 1% OZ increased by 3.1- and 2-fold respectively over levels in roots stored in air by day 7. Alcohol dehydrogenase (ADH) activities in roots exposed to 0% or 1% OZ increased by 1.6- and 1.7-fold respectively over levels in roots stored in air by day 7. ADH-specific activity was about 10-times that of PDC. The pH of root homogenate exposed to air remained constant, whereas the pH increased and decreased, respectively, in roots stored at 0% or 1 % O-2. PDC showed stability over the pH range 5.5-7.0, whereas ADH exhibited stability over the pH range 6.0-7.5. The Km of PDC in sweetpotato was 0.56 mM for pyruvate, whereas the Km of ADH was 0.19 mM for acetaldehyde. From these results, there may be some potential for the short-term exposure of sweetpotato roots to low 02 in place of low temperature treatment to prolong shelf-life, although ethanol fermentation may be accelerated under low OZ atmospheres.
  • Erratum: Effect of short-term anaerobic conditions on the production of volatiles, activity of alcohol acetyltransferase and other quality traits of ripened bananas (Journal of the Science of Food and Agriculture (August 15, 2006) 86, (1475-1480)), Sumithra K. Wendakoon, Yoshinori Ueda, Yoshihiro Imahori, Megumi Ishimaru, Journal of the Science of Food and Agriculture, Journal of the Science of Food and Agriculture, 86(13), 2241, Oct. 2006 , Refereed
  • Effect of short-term anaerobic conditions on the production of volatiles, activity of alcohol acetyltransferase and other quality traits of ripened bananas, Sumithra K. Wendakoon, Yoshinori Ueda, Yoshihiro Imahori, Megumi Ishimaru, JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, 86(10), 1475 - 1480, Aug. 2006
    Summary:Yellow, ripened (yellow with green tips) bananas were treated with nitrogen gas for 12, 24 and 48 h at 20 degrees C to study the effects of anaerobic conditions on the fruit quality, including the production of volatile compounds and activity of alcohol acetyltransferase (AAT) during the post-harvest period. Significantly higher concentrations of acetaldehyde and ethanol were found in the treated fruit than in the untreated bananas after removal from the conditions. The 48-h treatment showed higher levels of ethanol and acetaldehyde after storage. Immediately after releasing the fruit from the anaerobic atmosphere, the amounts of isobutyl acetate and isoamyl acetate decreased. The production of ethyl acetate increased markedly in each treatment unit 1 day after removing the fruit. Regardless of recovery from the production of isobutyl acetate and isoamyl acetate 1 day after treatment, the banana-like aroma was denatured because of the production of high levels of ethyl acetate and ethanol. The increase in AAT was slightly lower in nitrogen-treated fruit than untreated fruit. However, the activity in treated fruit was sufficient for ester production in bananas. The endogenous alcohol levels were increased during nitrogen gas treatment in the fruit due to the inhibition of ester production. Colour development of the bananas was greatly inhibited by the treatments, while the sugar content did not show any differences between the treated and untreated fruit. The results suggest that, even if bananas are removed from the short-term anaerobic conditions, a loss in quality, except sweetness, easily occurs afterwards, especially the characteristic aroma of the fruit during the post-harvest period. (c) 2006 Society of Chemical Industry.
  • Regulation of O-2 levels in controlled atmosphere storage on the respiratory and activity of TCA cycle relates enzymes in cucumber fruit, V. Srilaong, Y. Tatsumi, M. Ishimaru, PROCEEDINGS OF THE IVTH INTERNATIONAL CONFERENCE ON MANAGING QUALITY IN CHAINS, VOLS 1 AND 2, PROCEEDINGS OF THE IVTH INTERNATIONAL CONFERENCE ON MANAGING QUALITY IN CHAINS, VOLS 1 AND 2, 712(712), 661 - +, 2006
    Summary:Respiratory pattern and succinate dehydrogenase (SDH) activity in cucumber fruit stored in 5%, 21% (air control) and 100% O-2 at 5 degrees C were studied. Storage in 100% O-2 at 5 degrees C was most effective for suppressing the respiratory rate in cucumber fruit, the rate being lower than in fruit stored in either 5% O-2 or air. Relative activity of SDH in cucumber fruit stored in 100% O-2 was lower than in other storage conditions. Only slightly different SDH activity was recorded between control and 5% O-2-treated fruit. Northern hybridization with a partial cDNA of cucumber sdhB as a probe revealed a constant level of shdB gene expression during storage. These results suggesting that change of SDH is post-transcriptionally regulated.
  • Effects of the storage conditions of burdock (Arctium lappa L.) root on the quality of heat-processed burdock sticks, M Ishimaru, K Kagoroku, K Chachin, Y Imahori, Y Ueda, SCIENTIA HORTICULTURAE, SCIENTIA HORTICULTURAE, 101(1-2), 1 - 10, May 2004 , Refereed
    Summary:Polyethylene film and corrugated cardboard were used to package and store burdock roots (Arctium lappa L.) at 2, 8, and 20degreesC in an attempt to maintain the good appearance of heat-processed burdock sticks. The weight loss was as high as 60% of fresh weight when corrugated cardboard cartons were used for storage at 20degreesC. However, polyethylene bag packaging or low temperature storage resulted in lower levels of weight loss (less than 30%). To control the formation of white solids in exudate from processed sticks, low temperatures (2 degreesC) and storage of burdock roots for more than 30 days before processing were used to maintain the good appearance of burdock sticks. There was a significant decline in sugar content during storage at 8 and 20 degreesC, corresponding to an increased production of white solids. The fructan composition of raw burdock roots decreased faster to about 60% after storage for 30 days at 2 degreesC than at other storage temperatures (to about 30%). Inulinase activity in burdock roots stored at 2 degreesC was higher than in those stored at 8 and 20 degreesC. The amount of muddy exudate and the sugar content in solutions surrounding burdock sticks were related to the storage temperature before processing. These results indicate that the storage of burdock roots in polyethylene film packaging for 30 days at 2 degreesC is suitable to prevent the formation of muddy precipitate in processed burdock sticks. (C) 2003 Elsevier B.V. All tights reserved.
  • Inhibition of acetate ester biosynthesis in banana (Musa sapientum L.) fruit pulp under anaerobic conditions, SK Wendakoon, Y Ueda, Y Imahori, M Ishimaru, JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY, JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY, 52(6), 1615 - 1620, Mar. 2004 , Refereed
    Summary:The effect of anaerobic conditions on acetate ester biosynthesis in ripened banana pulp was investigated. Incubation of the pulp in less than 1% O(2) resulted in a significant reduction in the formation of ethyl acetate. Regardless of the presence of a large amount of endogenous ethanol and the remaining exogenous isobutyl alcohol after complete anaerobic incubation with the pulp, the production of acetate ester decreased. The effect of addition of pyruvate, isobutyl alcohol, acetate, and methyl hexanoate on acetate ester formation in 100% N(2) was also investigated. The addition of pyruvate and isobutyl alcohol to the pulp gave lower acetate esters in N(2) than in air, whereas the pulp incubated with acetate and isobutyl alcohol produced more acetate ester in both conditions. Therefore, the lack of acetyl CoA, or more precisely acetate, in the tissue is the main reason for the inhibition of acetate ester formation under anaerobic conditions. The activity of beta-oxidation measured by incubation with methyl hexanoate was detected only in the samples incubated in air. The formation of acetyl CoA, derived from pyruvate through mitochondria and through beta-oxidation, was inhibited by anaerobic conditions, which suggests that mitochondrial activity and/or beta-oxidation are essential for ester biosynthesis.
  • Regulation of fermentative metabolism in tomato fruit under low oxygen stress, Y. Imahori, K. Matushita, M. Kota, Y. Ueda, M. Ishimaru, K. Chachin, Journal of Horticultural Science and Biotechnology, Journal of Horticultural Science and Biotechnology, 78(3), 386 - 393, 2003 , Refereed
    Summary:Tomato fruit was stored under a continuous flow of 0% and 3% O2 (balance N2) or air for 7 d at 20°C to study the regulation of fermentative metabolism. The concentrations of ethanol and acetaldehyde were very low during storage at 3% O2 and air. At 0% O2, ethanol and to a lesser extent acetaldehyde, rapidly accumulated in the tissue. However, lactate concentration did not change during the experiment and was not significantly influenced by O2 concentration. Pyruvate decarboxylase (PDC) activity greatly increased in fruit exposed to 3% O2, while activity in fruit exposed to 0% O2 was the same level as the control. Alcohol dehydrogenase (ADH) activity greatly increased in fruit exposed to 3%, but at 0% O2 was the same level as the control. Lactate dehydrogenase (LDH) activity greatly increased in fruit exposed to 3%, but at 0% O2 was the same level as the control. The ADH activity in tomato fruit was about ten times greater than that of PDC activity and about 100 times greater than that of LDH activity during storage. Concentration of NADH in fruit exposed to 3% O2 was greater than that in fruit exposed to 0% O2 and air. Concentrations of pyruvate did not change during storage at 1% O2 and air. At 0% O2, pyruvate rapidly accumulated in its tissue. The Km of ADH in tomato fruit was 0.28 mM for acetaldehyde, and 0.058 mM for NADH. The Km of PDC in tomato fruit was 0.38 mM for pyruvate. The Km of LDH in tomato fruit was 0.18 mM for pyruvate. Possible regulation of fermentative metabolism is briefly considered.
  • Abscisic acid and 2,4-dichlorophenoxyacetic acid affect the expression of anthocyanin biosynthetic pathway genes in 'Kyoho' grape berries, T. Ban, M. Ishimaru, S. Kobayashi, S. Shiozaki, N. Goto-Yamamoto, S. Horiuchi, Journal of Horticultural Science and Biotechnology, Journal of Horticultural Science and Biotechnology, 78(4), 586 - 589, 2003 , Refereed
    Summary:The effects of abscisic acid (ABA) and 2,4-dichlorophenoxyacetic acid (2,4-D) on the expression of seven anthocyanin biosynthetic pathway genes in 'Kyoho' grape berries were investigated. In untreated berries, the expression of the UDP-glucose-flavonoid: 3-O-glucosyltransferase (UFGT) gene was detected only at 42 d after full bloom (DAB), whereas the phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone-3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR) and leucoanthocyanidin dioxygenase (LDOX) genes were expressed throughout the growing period. ABA increased anthocyanin content in the skin and the expression of PAL, CHS, CHI, DFR and UFGT genes at 7 d after treatment. In contrast, 2,4-D inhibited the accumulation of anthocyanin and the expression of all the genes examined. The results clearly show that the anthocyanin levels resulting from the application of ABA and 2,4-D were correlated with the expression of anthocyanin biosynthetic pathway genes.
  • Myb-related genes of the Kyoho grape (Vitis labruscana) regulate anthocyanin biosynthesis, S Kobayashi, M Ishimaru, K Hiraoka, C Honda, PLANTA, PLANTA, 215(6), 924 - 933, Oct. 2002 , Refereed
    Summary:Partial cDNAs of myb-related regulatory genes were isolated from the tetraploid Kyoho grape (Vitis labruscana: V. labrusea x V. vinifera) and the expression patterns of the corresponding genes were studied. Since MybA gene expression is closely related to coloring and/or ripening of the berry (expression increases strongly with the commencement of coloring and berry softening, and is detected only in berry skin and flesh), full-length cDNAs for the gene were isolated from a mature-berry cDNA library. Three different species of MybA were identified from the cDNA sequences. Delivery of these cDNAs to somatic embryos of grape led to the induction of reddish-purple spots and UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) gene expression in non-colored embryos. The UFGT transcript was not detected in control embryos, while other structural genes for anthocyanin biosynthesis were expressed in both control and pigmented embryos. In addition, introduction of the UFGT gene induced the same reddish-purple spots in embryos. In contrast, treatment with the leucoanthocyanidin dioxygenase (LDOX) gene failed to induce these spots. Our results strongly suggest that MybA genes are involved in the regulation of anthocyanin biosynthesis in the grape via expression of the UFGT gene.
  • Regulation of ethanolic fermentation in bell pepper fruit under low oxygen stress, Yoshihiro Imahori, Mika Kota, Yoshinori Ueda, Megumi Ishimaru, Kazuo Cachin, Postharvest Biology and Technology, Postharvest Biology and Technology, 25(2), 159 - 167, 2002 , Refereed
    Summary:Bell pepper fruit were stored under a continuous flow of 0 and 1% O2 (balance N2) or air for 7 days at 20°C to study the regulation of ethanolic fermentation. The concentrations of ethanol and acetaldehyde were very low during storage at 1% O2 and air. At 0% O2, ethanol and to a lesser extent acetaldehyde, rapidly accumulated in the tissue. Pyruvate decarboxylase (PDC) activity greatly increased in fruit exposed to 1% O2, while activity in fruit exposed to 0% was only slightly higher than that of the control. Alcohol dehydrogenase (ADH) activity greatly increased in fruit exposed to 1% but at 0% O2 was at the same level as the control. The activity of ADH was about 10 times that of PDC during storage. Changes in ADH isozymes correlated well with changes in ADH activity. Concentration of NADH did not change during storage in air, but in fruit in 0 and 1% O2 showed a significant increase. Concentrations of pyruvate were very low and did not change during storage at 1% O2 and air. At 0% O2, pyruvate rapidly accumulated in the tissue. The Km of ADH in bell pepper fruit was 0.74 mM for acetaldehyde, and 0.33 mM for NADH. The Km of PDC in bell pepper fruit was 0.92 mM for pyruvate. Possible regulation of ethanolic fermentation is briefly considered. © 2002 Elsevier Science B.V. All rights reserved.
  • Expression of a xyloglucan endo-transglycosylase gene is closely related to grape berry softening, Megumi Ishimaru, Shozo Kobayashi, Plant Science, Plant Science, 162(4), 621 - 628, 2002 , Refereed
    Summary:Six partial cDNAs for cell wall degradation-related enzymes, xyloglucan endo-transglycosylase (XET), polygalacturonase (PG), pectin methylesterase (PME), pectate lyase (PL), cellulase (Cel), and β-D-galactosidase (GAL), were isolated from a véraison -specific subtractive library made from Kyoho grape (Vitis labruscana) berries. During the development of Kyoho grape berries, the expression of these genes was analyzed. Among the genes analyzed, XET gene expression was closely related to berry softening slight XET gene expression was detected before véraison and was markedly increased at véraison (the stage of the onset of berry softening). In addition, the expression of the gene was berry specific. In the other genes, except for PL, however, no expression was detected during the berry development PL was detected only after the coloring stage began. These observations suggest that XET plays an important role in grape berry softening. To obtain further information about this gene, a full-length cDNA clone (VXET 1) encoding XET was isolated from a cDNA library of Kyoho grape berries and characterized. The VXET 1 was 1326 bp in length and contained a 5′-untranslated region of 67 bp, an open reading frame of 873 bp, and a 3′-untranslated region of 386 bp. The deduced amino acid sequence of the VXET 1 showed 73.5% identity with the corresponding XET (NXG 1) from nasturtium (Tropaeolum majus) that has been shown to have endo-glucanase activity. These findings suggest that the VXET 1 product cleaves a cellulose-xyloglucan network of cell wall and induces the softening of Kyoho grape berries at véraison. © 2002 Elsevier Science Ireland Ltd. All rights reserved.
  • Physiological responses and quality attributes of Japanese pear 'Kosui' fruit kept in low oxygen atmospheres, Y. Imahori, I. Kishioka, K. Uemura, H. Yoshioka, Y. Ueda, M. Ishimaru, K. Chachin, Journal of Horticultural Science and Biotechnology, Journal of Horticultural Science and Biotechnology, 77(6), 677 - 682, 2002 , Refereed
    Summary:Japanese pear 'Kosui' fruits were stored under a continuous flow of 0%, 1%, 3%, 5% and 10% O2 (balance N2) or air for 7 d at 20°C to study the effects of low O2 on their physiological responses and quality attributes. Low O2 treatments did not significantly influence changes in skin colour and soluble solids content. However, weak off-flavours were detected in the fruits stored at 0% O2 on day 3, and the intensity of these off-flavours increased as storage progressed. The concentrations of acetaldehyde in fruit increased throughout the storage period. The ethanol concentration was greatly increased in fruits stored at 0% O2. Moreover, ethanol concentrations were much higher than those of acetaldehyde and remained very low during storage in air, but their concentration were just slightly increased in fruits exposed to 1%, 3%, 5% and 10% O2. Pyruvate decarboxylase activity was greatly increased in fruits exposed to 1% and 3% O2, while its activity in fruits exposed to 5% and 10% O2 were only slightly higher than that of the control and at 0% O2 at the same level as the control. Alcohol dehydrogenase (ADH) activity greatly increased in fruit exposed to 0%, 1%, 3% and 5% O2, while at 10% O2, ADH was only slightly higher than the control. Changes in ADH isozymes correlated well with changes in ADH activity. The homogenate pH of fruits exposed to 1%, 3%, 5% and 10% O2 and air remained constant, while in fruit stored at 0% O2 their pH increased. The potential for using low O2 atmospheres to help in maintaining the quality of Japanese pear 'Kosui' is discussed.
  • Comparison of UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) gene sequences between white grapes (Vitis vinifera) and their sports with red skin, S. Kobayashi, M. Ishimaru, C. K. Ding, H. Yakushiji, N. Goto, Plant Science, Plant Science, 160(3), 543 - 550, Feb. 05 2001 , Refereed
    Summary:The expression of the UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) gene has been shown to be critical for anthocyanin biosynthesis in the grape berry. Using white cultivars and bud sports with red skin, we examined the expression of seven anthocyanin biosynthetic genes including the UFGT gene and compared the coding/promoter sequences of the UFGT gene. Northern blot analysis showed that the seven anthocyanin biosynthetic genes were expressed coordinately at higher levels in the red-skin sports than in the white-skin progenitors of the sports. It was especially notable that UFGT gene expression was detected only in the red-skin sports and Kyoho. However, there were no differences in either coding or promoter sequences between Italia (Vitis vinifera) and its red-skin sport Ruby Okuyama, or between Muscat of Alexandria (V. vinifera) and the red-skin sport Flame Muscat. From these findings, the phenotypic change from white to red in the sports is thought to be the result of a mutation in a regulatory gene controlling the expression of UFGT. © 2001 Elsevier Science Ireland Ltd.

Misc

  • Structural and functional analysis of tomato beta-galactosidase 4: insight into the substrate specificity of the fruit softening-related enzyme (vol 86, pg 300, 2016), Masahiro Eda, Takashi Matsumoto, Tatsuji Sakamoto, Megumi Ishimaru, Toshiji Tada, PLANT JOURNAL, 90, 3, 621, 621,   2017 05 , 10.1111/tpj.13507
  • Enzymatic Properties of Yeast Expressed Tomato Beta-galactosidase (TBG)1, Megumi Ishimaru, Hidemi Izumi, Tatsuji Sakamoto, Toshihisa Kotake, Yoichi Tsumuraya, HORTSCIENCE, 45, 8, S289, S289,   2010 08
  • Effect of short-term anaerobic conditions on the production of volatiles, activity of alcohol acetyltransferase and other quality traits of ripened bananas (vol 86, pg 1475, 2006), Sumithra K. Wendakoon, Yoshinori Ueda, Yoshihiro Imahori, Megumi Ishimaru, JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, 86, 13, 2241, 2241,   2006 10 , 10.1002/jsfa.2695
  • Effects of continuous exposure to 100% CO2 or a combination of 100% CO2 and its gradual reduction to 0% on ethylene production in Japanese persimmon 'Tonewase' fruit, M Ishimaru, T Yamamoto, A Morioka, Y Ueda, K Chachin, JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE, 68, 4, 890, 896,   1999 07 , 10.2503/jjshs.68.890, http://www.scopus.com/inward/record.url?partnerID=HzOxMe3b&scp=0032787725&origin=inward
    Summary:Immature and mature Japanese persimmon 'Tonewase' fruit were treated with 1) 100% CO2 for24 hr (control) or 2) 100% CO2 for 17 hr and gradual reduction to 0% CO2 for 7 hr (combination treatment) to remove their astringency; a third group was left untreated. The levels of 1-aminocyclopropane-1-carboxylic acid (ACC) and ACC synthase and ACC oxidase activities in their extracts were analyzed. The effects of adding catechin and bovine serum (BSA) separately to the extraction medium on the enzyme activities were also determined. 1. The ACC content in immature untreated and control fruit rapidly increased. during storage at 20 degrees C, whereas that in fruits exposed to the combination treatment remained low during storage. Mature treated fruits responded similarly to the immature treated ones. 2. The ACC synthase activity of immature fruit exposed to the combination treatment remained very low compared to the untreated and control fruit. The ACC synthase activity of immature fruit was significantly inhibited by the combination treatment compared to that of mature fruit. 3. The ACC oxidase activity in both immature and mature fruit was less inhibited by the combination treatment, compared to ACC synthase activity. 4. The ACC synthase activity was inhibited by the addition of catechin in the extraction medium but it was promoted by the addition of BSA. These results indicate that the inhibition of ethylene evolution by Japanese persimmon 'Tonewase' with 100% CO2 for 24 hr or the combination treatment in which CO2 is reduced to 0% may be attributed to the blockage of S-adenosylmethionine conversion to ACC.
  • Effects of continuous exposure to 100% CO2or a combination of 100% CO2 and its gradual Reduction to 0% on ethylene production in Japanese persimmon 'Tnewase'fruit, Megumi Ishimaru, Takashi Yamamoto, Akira Morioka, Yoshinori Ueda, Kazuo Chachin, Journal of Japanese Society of Horticutural Science, 68, 4, 890, 896,   1999 , 10.2503/jjshs.68.890
  • Effects of the combination of continuous exposure and gradual reduction of carbon dioxide (CO2) on the firmness of Japanese persimmon 'Tonewase' fruit, M Ishimaru, T Yamamoto, K Chachin, JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE, 67, 5, 812, 814,   1998 09 , 10.2503/jjshs.67.812, http://www.scopus.com/inward/record.url?partnerID=HzOxMe3b&scp=0032464185&origin=inward
    Summary:Two experiments were conducted to test the effects of exposing Japanese persimmon 'Tone-wase' fruit harvested at different maturies to varying concentrations of carbon dioxide on firmness, the evolution of ethylene and respiration. In Phase I, the fruits were exposed to ambient air and to 100% carbon dioxide for 24 hr (control) and subsequently stored at 20 degrees C. In Exp. I, Phase I was repeated on immature fruit and the third treatment was added in which the carbon dioxide concentration was decreased from 100% to 0% after 17 hr. In Exp. II, the procedure was similar to that in Exp. I, except that more mature fruits were used and the carbon dioxide concentration was reduced from 100% to 0% after 6, 12 and 20 hr. 1. The fruits of the Japanese persimmon 'Tonewase' exposed to ambient air and those treated continuously with 100% carbon dioxide softened equally fast and ripened within 6 days. 2. Slightly immature fruits exposed to air and 100% carbon dioxide softened as in Phase I, whereas those exposed to 100% carbon dioxide for 17 hr were still firm after 2 weeks in storage. 3. Fruits exposed to air and 100% carbon dioxide softened as did those in Phase I, wheras those exposed to 100% carbon dioxide for 6, 12 and 20 hrs maintained their firmness longer during storage.
  • Effects of 'on-tree removal'of astringency by ethanol treatment on B-D-galactosidase gene expression of Japanese persimmon 'Tonewase'fruit, Applied Biological Sciecne, 4, 77, 83,   1998
  • Effects of the Combination of continuous exposure and gradual reduction of carbon dioxide(CO2)on the firmnes of Japanese persimmnon'Tonewase'fruit, Megumi Ishimaru, Takashi Yamamoto, Kazuo Chachin, Journal of Japanese Society of Horticultural Science, 67, 5, 812, 814,   1998 , 10.2503/jjshs.67.812

Research Grants & Projects

  • Ministry of Education, Culture, Sports, Science and Technology, Grants-in-Aid for Scientific Research(基盤研究(C)), Structural based fruit softening mechanism; the model of tomato fruit softening during maturation, In tomato fruit, beta-galactosidase 4 (TBG4) is an enzyme responsible for fruit softening through the degradation of beta-(1,4)-galactan in the pericarp cell wall. To gain structural insight into the substrate specificity, we determined the crystal structures of TBG4 and its complex with beta-D-galactose. TBG4 was composed of a catalytic TIM barrel domain followed by three beta-sandwich domains. This structure is similar to other beta-galactosidase belong to GH35 families.In addition, we determined the enzymatic properties and substrate specificities of TBG1. TBG4 has substrate recognition to beta-(1,4)-linkage, however, TBG1 has beta-(1,3) and beta-(1,6)-likage substrate.In these results, TBG's act on the tomato cell wall during fruits development and maturation, and seberal stage of tomato fruits cell walls construct/reconstruct to some components sugar as a substrate against TBG's.
  • Ministry of Education, Culture, Sports, Science and Technology, Grants-in-Aid for Scientific Research(基盤研究(B)), Quality maintenance in postharvest horticultural crops by stress treatments and development of novel storage methods, Effects of stress treatments such as heat, ethanol, UV-B and hydrogen peroxide application on quality maintenance in postharvest horticultural crops were determined by physiological, biochemical and molecular biological analyses. Appropriate conditions of each stress treatment for keeping quality during storage were also studied. These findings obtained suggest that stress treatments make it possible to maintain postharvest storage quality of horticultural crops due to the generation of active oxygen species and the activation of scavenging system, the control of ethylene production, and the maintenance of chemical components. Furthermore, stress treatments seem to lead to novel storage and transport technologies.
  • Ministry of Education, Culture, Sports, Science and Technology, Grants-in-Aid for Scientific Research(基盤研究(C)), Molecular and cellular approach for fruit softening on grape berries during fruit development and maturation
  • Cloning and analysis of acetyl Co A transferase gene from melon fruit
  • Cloning and analysis of ripening-related genes from grape berries