Hiroyuki Itamura

Shimane University, Matsu, Shimane, Japan

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Publications (51)28.6 Total impact

  • Mari Sugiyama · Takuya Katsube · Akio Koyama · Hiroyuki Itamura
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    ABSTRACT: Background: The functional components of mulberry leaves have attracted the attention of the health food industry, and increasing their concentrations is an industry goal. We investigated the effects of solar radiation, which may influence the production of flavonol and 1-deoxynojirimycin (DNJ) functional components in mulberry leaves, by comparing a greenhouse (poor solar radiation) and outdoor (rich solar radiation) setting. Results: The level of flavonol in leaves cultivated in the greenhouse was markedly decreased when compared with those cultivated outdoors. In contrast, the DNJ content in greenhouse cultivated plants was increased only slightly when compared with those cultivated outdoors. Interestingly, the flavonol content was markedly increased in the upper leaves of mulberry trees that were transferred from a greenhouse to the outdoors compared with those cultivated only in the outdoors. Conclusion: Solar radiation conditions influence the synthesis of flavonol and DNJ, the functional component in mulberry leaves. Under high solar radiation, the flavonol level becomes very high but the DNJ level becomes slightly lower, suggesting that the impact of solar radiation is great on flavonol but is small on the DNJ synthesis.
    No preview · Article · Jan 2016 · Journal of the Science of Food and Agriculture
  • Yuka Suehiro · Keisuke Mochida · Hiroyuki Itamura · Tomoya Esumi
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    ABSTRACT: A recently popular Japanese yellow-green-skin table grape, 'Shine Muscat' (Vitis labruscana Bailey × V. vinifera L.), has the problem of berry skin browning, which occurs at the maturation stage just before harvest. Tiny reddish-brown blotches appear on the surface of berries and considerably decrease the grape's market value. Although the mechanisms and factors for browning are unknown, we hypothesized the involvement of polyphenol compounds and their oxidation reactions. In this study, the gene expressions of polyphenol oxidase (PPO), stilbene synthase (STS), and chalcone synthase (CHS), which are key enzymatic genes related to the metabolic pathway for polyphenols, were analyzed during berry maturation to examine the molecular basis for browning. Skin browning occurred on several berries in a bunch of 'Shine Muscat' from 80 days after full bloom (DAFB), after which the number of berries with skin browning increased, and the browned area spread on the berry surfaces with maturation. Increases in the expression of VvPPO2, VvSTS type B, and VvCHS1 were associated with skin browning, and the trans-resveratrol content also increased in the browning skin, suggesting that biosynthesis and metabolic pathways for phenolic compounds were activated at the time of browning. In terms of VvPPO genes, specific up-regulation of VvPPO2 expression was observed compared with the VvPPO1 gene. The promoter sequence of VvPPO2 contains more Myb binding motifs and W-box motifs than does VvPPO1. The specific up-regulation of VvPPO2 gene expression will play a crucial role in understanding and managing the skin-browning mechanism in the grape berries of 'Shine Muscat'. © 2014 The Japanese Society for Horticultural Science (JSHS), All right reserved.
    No preview · Article · Apr 2014 · Journal- Japanese Society for Horticultural Science
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    Mari Sugiyama · Takuya Katsube · Akio Koyama · Hiroyuki Itamura
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    ABSTRACT: The varietal differences in the flavonol glycosides rutin, isoquercitrin, kaempferol 3-(6-rhamnosylglucoside), quercetin 3-(6-malonylglucoside), astragalin, quercetin 3-(6-acetylglucoside) and kaempferol 3-(6-malonylglucoside) contained in mulberry leaves were elucidated. This information was used for breeding mulberry cultivars with a high concentration of functional components. The flavonol content, composition and proportion in leaves varied widely. 'Kobuchizawa 1' had the highest level of total flavonols (1819 mg/100 g dry weight), five times higher than that of 'Mikurasima 15' (393 mg/100 g dry weight). Quercetin 3-(6-malonylglucoside) was the most abundant flavonol, although it was not found in all cultivars. Quercetin 3-(6-acetylglucoside) was only found in 'Keguwa'. From the quercetin 3-(6-malonylglucoside) content in crossbred offspring, malonyltransferase, an enzyme involved in quercetin 3-(6-malonylglucoside) synthesis, was acquired according to Mendelian inheritance. An offspring with a higher quercetin 3-(6-malonylglucoside) level than both parents was obtained from the crossing. This suggested that crossbreeding was effective for acquiring cultivars with a higher content of quercetin 3-(6-malonylglucoside).
    Full-text · Article · Aug 2013 · Journal of Agricultural and Food Chemistry
  • H. Itamura · A. Nakatsuka · T. Adachi · M. Yoshioka
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    ABSTRACT: Persimmon (Diospyros kaki) fruit soften naturally on the tree during late autumn. We investigated the relationships among ethylene production, the cell wall degrading enzymes polygalacturonase (PG), pectinesterase (PE), β-D-galactosidase (β-D-Gal) and α-L-arabinofuranosidase (α-L-Arf), and on-tree softening of persimmon 'Saijo' fruit. Fruit were harvested from mid-September to late November from a commercial orchard in Matsue, Japan. Flesh firmness decreased gradually until early November and then decreased rapidly. Activity of PG decreased slightly in early October and thereafter was maintained at the same level until late November. Activity of PE increased during September and October and peaked in mid-November. Activity of β-D-Gal increased rapidly from mid to late November, whereas α-L-Arf activity increased rapidly from early to late November. Fruit that showed abnormal on-tree softening and fruit that represented a softening degree ranging from 1 (firm) to 4 (very soft or part of the peel ruptured) were harvested on the same date in late October and the activity of four cell wall degrading enzymes and internal ethylene concentration were determined. The internal ethylene concentration increased rapidly from softening degree 2 to 3. The activity of PE, β-D-Gal and α-L-Arf increased with advancing degree of softening. Consequently, on-tree fruit softening in late autumn might be caused by cell wall decomposition by the cooperative activities of PE, β-D-Gal, and α-L-Arf induced by ethylene synthesis.
    No preview · Article · Jun 2013 · Acta horticulturae
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    A. Nakatsuka · H. Itamura · K. Yano · R. Abe · T. Someya · T. Nakagawa
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    ABSTRACT: To improve our understanding of the molecular mechanism of rapid softening of persimmon (Diospyros kaki) 'Saijo' fruit on the tree prior to harvest, we constructed a cDNA library from softened pulp of immature fruit and analyzed expressed sequence tags (ESTs). Fruits that were rapidly softened on the tree were harvested at three softening index (from moderately soft to over-ripe) in early October. We sequenced 5728 randomly selected clones from the library, and obtained a total of 4701 ESTs (FY982194-FY986894). Following a sequence homology search, sequences for two 1-aminocyclopropane-1-carboxylate (ACC) synthase (Dk-ACS2 and Dk-ACS3) and two ACC oxidase (Dk-ACO1 and Dk-ACO2) cDNAs were isolated, as well as genes for pectinase, hemicellulase and cellulose- interacting protein. Notably, the β-D-galactosidase, xyloglucan endotransglycosylase (XTH), and expansin genes isolated from fruit rapidly softened on the tree showed sequence differences compared with those isolated previously from the ovary and young expanding fruit. One of the isolated genes, Dk-XTH1, was ethylene-dependent. These results suggest that rapid softening of persimmon fruit on the tree is related to ethylene synthesis and hemicellulose degradation. This study provides an initial overview of a set of genes that are expressed during softening of persimmon fruit.
    Full-text · Article · Jun 2013 · Acta horticulturae
  • N. Sun · Z. Tang · A. Nakatsuka · H. Itamura
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    ABSTRACT: Reports of 'tree factors' indicated that some climacteric fruits on a tree receive inhibitors of ripening or ethylene biosynthesis from leaves of the parent plants. In our study, the existence of 'tree factor' or 'tree ethylene-inhibitory factor' in persimmon was investigated, and different effects of the 'tree factor' were determined at a variety of developmental stages. Infiltration of a crude leaf extract (extracted in ethanol and dissolved in phosphate buffer), three leaf-extract fractions of different polarities (hexane, ethyl acetate, and aqueous fractions) and four plant hormones (ABA, GA3, IAA and zeatin) into young persimmon fruit flesh was conducted, and none of them inhibited endogenous ethylene production in flesh from detached fruit, thus the leaf extracts contained none of the expected 'tree factors'. Alternatively, we determined the effects of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU; a specific photosynthesis inhibitor) and defoliation treatments on photosynthetic rate, transpiration rate, sap flow, fruit drop, and ethylene evolution. DCMU treatment, which prevented photosynthate transport but allowed water flow, promoted fruit drop by 67% 10 days after treatment. The defoliation treatment, which prevented photosynthate and water transport, significantly hastened fruit drop. On average, fruit drop occurred 2 days earlier in the defoliation treatment than in the DCMU treatment. Overall, our results suggested that the transport of photosynthates, or both photosynthates and water, to fruit inhibits fruit drop by preventing induction of ethylene synthesis in young persimmon fruit. The finding of the candidates for 'tree factors' is expected to have important implications for the improvement of postharvest fruit quality and storability.
    No preview · Article · Jun 2013 · Acta horticulturae
  • H. Itamura · A. Nakatsuka · N. Sun · T. Esumi · A. Yamada · K. Yano · T. Nakagawa
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    ABSTRACT: Persimmon fruit soften easily and have a shorter shelf life than other fruit. Fruit softening is closely related to ethylene synthesis and cell wall degradation. In this study, persimmon fruit were treated with ascorbate after harvest, and the fruit softening and ethylene production rates were determined. Ascorbate treatment lowered ethylene production and prolonged the shelf life of persimmon fruit, compared with a water treatment and the control. Ascorbate may function to decrease ethylene production, thereby prolonging the shelf life of the fruit. We analyzed expressed sequence tags from three cDNA libraries from persimmon fruit, and obtained information about genes related to the ascorbate biosynthesis pathway. DNA microarray analyses showed that L-galactono-1, 4-lactone dehydrogenase genes were expressed more strongly in "Endou" fruit than in fruit of "B waisei", a fast-softening cultivar. These results suggest that the ability to accumulate ascorbate is related to softening of persimmon fruit, and that ascorbate may function as a radical scavenger.
    No preview · Article · May 2013 · Acta horticulturae
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    ABSTRACT: Persimmon (Diospyros kaki Thunb.) fruit undergoes intensive cell wall modification during postharvest fruit softening. Xyloglucan metabolism is important in cell wall disassembly. We cloned cDNAs for two xyloglucan endotransglycosylase/hydrolase genes (DkXTH1 and DkXTH2) from ‘Saijo’ persimmon fruit treated with dry ice to remove astringency. In order to determine the ethylene dependence of XTH gene expression, fruit were exposed to 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action, prior to removal of astringency. Ethylene production increased in mature control and 1-MCP-pretreated fruit after dry-ice treatment, and flesh firmness decreased to the same extent during dry-ice treatment in the control and 1-MCP-pretreated fruit. After dry-ice treatment, control fruit softened completely, but fruit firmness was maintained in 1-MCP-pretreated fruit. Accumulation of DkXTH1 mRNA was induced simultaneously with commencement of ethylene production in mature control fruit. Pretreatment with 1-MCP delayed accumulation of DkXTH1 mRNA. DkXTH2 expression also coincided with fruit softening but was intensified by 1-MCP treatment during the deastringency treatment. These results indicate that fruit softening was related to both DkXTH1 and DkXTH2 expression in ‘Saijo’ persimmons.
    Full-text · Article · Oct 2011 · Postharvest Biology and Technology
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    ABSTRACT: Flavonoids are ingested by the general population as anti-oxidant and anti-inflammatory agents. In this study, we investigated the effects of myricitrin, a flavonoid rich in Myrica rubra leaf, upon anti-inflammatory action. Myrica rubra leaf extracts inhibited pro-inflammatory TNFα production in a macrophage cell line, Raw264.7 cells. We observed that the serum IgE levels in the leaf extract-treated DO11.10, a mouse allergy model, were down-regulated. HPLC was performed to demonstrate that M. rubra leaf extracts contain a large amount of myricitrin. We observed an inhibitory effect of HPLC-purified myricitrin on TNFα production in Raw264.7 cells. Thus, myricitrin may be of potential interest in the management of inflammatory conditions.
    No preview · Article · Feb 2011 · Natural product research
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    ABSTRACT: In this study, we aimed to characterize which factors control ethylene production and fruit drop in persimmon (Diospyros kaki Thunb.). We determined the effects of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU; a specific photosynthesis inhibitor) and defoliation treatments on the photosynthetic rate, transpiration rate, sap flow, fruit drop, and ethylene evolution. DCMU treatment, which prevented photosynthate transport but allowed water flow, promoted fruit drop by 67% 10 days after treatment. Defoliation treatment, which prevented both photosynthate and water transport, significantly hastened fruit drop. On average, fruit drop occurred 2 days earlier with defoliation treatment than DCMU treatment. Compared with the control, treated fruit attached to the tree showed an increasing trend in ethylene production, although at a low level (≤ 0.8 nL.g-1.h-1 in the flesh; ≤ 20 nL.g-1.h-1 in the calyx). Fruit abscission is thought to be induced by a following ethylene burst, because fruit showing an abscission trend showed high rates of ethylene production (almost 200 nL.g-1.h-1). Thus, blocking photosynthate transport and water flow induced initial and autocatalytic increases in the production of ethylene, which plays a crucial role in triggering fruit drop. Overall, our results suggest that the transport of photosynthates, or both photosynthates and water, to fruit inhibits fruit drop by preventing the induction of ethylene synthesis in young persimmon fruit. JSHS
    No preview · Article · Oct 2010
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    ABSTRACT: The grape berry morphologically consists of epidermis, an outer wall, an inner wall and placenta. The inner contents such as soluble solids, organic acids and moisture distribution of grape berries are dramatically changed during the véraison between the growth and ripening period. However, we know little about the changes in the inner contents of the outer wall, inner wall and placenta. Our purpose of the study is to clarify the tissue specificity of the total soluble solids content, sugar composition, flesh firmness and moisture distribution of 'Kyoho' grape berry during growth and ripening period. The moisture distribution of the grape berries was analyzed with magnetic resonance imaging (MRI). The total soluble solids contents of the outer wall were higher than those of the inner wall during the investigation period. In this study, fructose, glucose and sucrose were detected in the berries. The concentrations of these sugars in the outer wall were higher than those in the inner wall; however, the components of these sugars were not different between the outer wall and inner wall. Even within the same berry, the flesh firmness and the moisture distribution were different from one part of the tissue to another. These results indicate that the growth rate of grape berry varies considerably among the different parts of the berry.
    No preview · Article · Jul 2010 · Journal of Applied Horticulture
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    Full-text · Article · Jan 2010 · Horticultural Research (Japan)
  • H. Itamura · T. Nakamoto · Y. Hanaoka · N. Sun

    No preview · Article · Jun 2009 · Acta horticulturae
  • Keisuke MOCHIDA · Hiroyuki ITAMURA
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    ABSTRACT: Cold tolerance was compared among the three ‘Saijo’ persimmon strains “Abe”, “Endo”, and “Izumo”. We also determined the carbohydrate and non-tannin flavans content (mainly anthocyanins) in the stems and buds of 1-year-old twigs of the three strains. In “Abe”, the total sugar content in stems in early spring, just before sprouting, was significantly lower than those of “Endo” and “Izumo”. This was because the amounts of sucrose and sorbitol contained in “Abe” were significantly lower than those in the other two strains. The glucose content of “Abe” buds in early spring was likewise significantly lower than that of the other two strains. The non-tannin flavan contents of the buds and bark tissues of “Abe” stems were lower than those of “Endo”, while in mid-March the electrolyte leakage of stems and buds of “Abe” during treatments at -3 and -6°C was found to be significantly higher than in the other two strains. Browning was observed in “Abe” on stems after treatment at -3°C, and on cambiums after treatment at -6°C. Our results showed that “Abe” is the least tolerant to cold among the three strains. The sprouting disorders frequently observed in “Abe” may result from slight freezing injuries to buds.
    No preview · Article · Jan 2009 · Journal of Agricultural Meteorology

  • No preview · Article · Jan 2009 · Horticultural Research (Japan)

  • No preview · Article · Dec 2008 · Acta horticulturae
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    ABSTRACT: Persimmon (Diospyros kaki Thunb.) is an important fruit in Asian countries, where it is eaten as a fresh fruit and is also used for many other purposes. To understand the molecular mechanism of fruit development and ripening in persimmon, we generated a total of 9,952 expressed sequence tags (ESTs) from randomly selected clones of two different cDNA libraries. One cDNA library was derived from fruit of "Saijo" persimmon at an early stage of development, and the other from ripening fruit. These ESTs were clustered into 6,700 non-redundant sequences. Of the 6,700 non-redundant sequences evaluated, the deduced amino acid sequences of 4,356 (65%) showed significant homology to known proteins, and 2,344 (35%) showed no significant similarity to any known proteins in Arabidopsis databases. We report comparison of genes identified in the two cDNA libraries and describe some putative genes involved in proanthocyanidin and carotenoid synthesis. This study provides the first global overview of a set of genes that are expressed during fruit development and ripening in persimmon.
    Full-text · Article · Jun 2008 · Plant Cell Reports
  • Keisuke Mochida · Takao Kurahashi · Yasuyuki Togano · Hiroyuki Itamura

    No preview · Article · Jan 2008 · Horticultural Research (Japan)
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    ABSTRACT: The mature leaves of Japanese 'Saijo' persimmon (Diospyros kaki Thunb.) are consumed as ingredients in health foods and teas. Levels of ascorbic acid and polyphenols were compared between the mature leaf (M-leaf), young shoot (T-shoot; cultured by water-soaking twigs grown the previous year) and adventitious shoot (A-shoot; obtained from orchard trees). The level of total ascorbic acid (T-AsA) was highest in M-leaves, and though the levels of polyphenols were high in M-leaf and A-shoot, they were remarkably low in T-shoot. Isoquercitrin and astragalin levels were highest in A-shoot, followed by M-leaf, and then T-shoot.
    Full-text · Article · Jan 2008 · Food Science and Technology Research
  • Kazuyuki Akaura · Ningjing Sun · Hiroyuki Itamura

    No preview · Article · Jan 2008 · Horticultural Research (Japan)