The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform

Seiichiro Kamisaka - One of the best experts on this subject based on the ideXlab platform.

  • increase in the level of arabinoxylan hydroxycinnamate network in cell walls of wheat Coleoptiles grown under continuous hypergravity conditions
    Physiologia Plantarum, 2005
    Co-Authors: Kazuyuki Wakabayashi, Seiichiro Kamisaka, Kouichi Soga, Takayuki Hoson
    Abstract:

    Changes in the amount and composition of cell wall constituents in response to continuous hypergravity stimuli were studied in wheat (Triticum aestivum L.) Coleoptiles. The lengths of Coleoptiles grown under hypergravity (300 g) conditions for 2-4 days from germination stage were 60-70% of those of 1 g control. However, the net amounts of hemicellulosic polysaccharides and cellulose in hypergravity-treated Coleoptiles increased progressively as much as those in the control Coleoptiles. As a result, their contents per unit length of coleoptile largely increased under hypergravity conditions. In the hemicellulose fraction, the amounts of arabinose and xylose, the major components of the fraction, prominently increased in response to hypergravity. When hemicellulosic polysaccharides were separated into neutral and acidic polymers by an anion-exchange column, the amounts of the acidic fraction consisting of (glucurono)arabinoxylans were higher in hypergravity-treated Coleoptiles than in control Coleoptiles. The amounts of cell wall-bound ferulic acid and diferulic acid (DFA) increased dramatically in both 1 g control and hypergravity-treated Coleoptiles. Particularly, the amounts of DFA in hypergravity-treated Coleoptiles were significantly higher than those in control Coleoptiles during the incubation period. These results suggest that continuous hypergravity increases the rigid network structures via arabinoxylan-hydroxycinnamate cross-links within cell wall architecture in wheat Coleoptiles. These structures may have a load-bearing function and contribute to construct the stable cell wall against the gravitational force.

  • Modification of cell wall architecture of wheat Coleoptiles grown under hypergravity conditions.
    Uchu Seibutsu Kagaku, 2003
    Co-Authors: Kazuyuki Wakabayashi, Seiichiro Kamisaka, Kouichi Soga, Takayuki Hoson
    Abstract:

    Cell wall structure of wheat Coleoptiles grown under continuous hypergravity (300 g) conditions was investigated. Length of Coleoptiles exposed to hypergravity for 2-4 days from germination stage was 60-70% of that of 1 g control. The amounts of cell wall polysaccharides substantially increased during the incubation period both in 1 g control and hypergravity-treated Coleoptiles. As a results, the levels of cell wall polysaccharides per unit length of coleoptile, which mean the thickness of cell walls, largely increased under hypergravity conditions. The major sugar components of the hemicellulose fraction, a polymer fraction extracted from cell walls with strong alkali, were arabinose (Ara), xylose (Xyl) and glucose (Glc). The molar ratios of Ara and Xyl to Glc in hypergravity-treated Coleoptiles were higher than those in control Coleoptiles. Furthermore, the fractionation of hemicellulosic polymers into the neutral and acidic polymers by the anion-exchange column showed that the levels of acidic polymers in cell walls of hypergravity-treated Coleoptiles were higher than those of control Coleoptiles. These results suggest that hypergravity stimuli bias the synthesis of hemicellulosic polysaccharides and increase the proportion of acidic polymers, such as arabinoxylans, in cell walls of wheat Coleoptiles. These structural changes in cell walls may contribute to plant resistance to hypergravity stimuli.

  • increased molecular mass of hemicellulosic polysaccharides is involved in growth inhibition of maize Coleoptiles and mesocotyls under hypergravity conditions
    Journal of Plant Research, 1999
    Co-Authors: Kouichi Soga, Takayuki Hoson, Kazuyuki Wakabayashi, Keita Harada, Seiichiro Kamisaka
    Abstract:

    mays L. cv. Cross Bantam T51) Coleoptiles and mesocotyls was suppressed by hypergravity at 30 g and above. Acceleration at 300 g significantly decreased the mechanical extensibility of cell walls of both organs. Hypergravity increased the amounts of hemicellulose and cellulose per unit length in mesocotyl walls, but not in coleoptile walls. The weight-average molecular masses of hemicellulosic polysaccharides were also increased by hypergravity in both organs. On the other hand, the activities of β-glucanases extracted from coleoptile and mesocotyl cell walls were decreased by hypergravity. These results suggest that the decreased activities of β-glucanases by hypergravity cause an increase in the molecular mass of hemicellulosic polysaccharides of both organs. The upshift of molecular mass of hemicellulosic polysaccharides as well as the thickening of cell walls under hypergravity conditions seems to be involved in making the cell wall mechanically rigid, thereby inhibiting elongation growth of maize Coleoptiles and mesocotyls.

  • Suppression of cell wall stiffening along Coleoptiles of wheat (Triticum aestivum L.) seedlings grown under osmotic stress conditions
    Journal of Plant Research, 1997
    Co-Authors: Kazuyuki Wakabayashi, Takayuki Hoson, Seiichiro Kamisaka
    Abstract:

    Effects of polyethylene glycol (PEG)-induced osmotic stress on the mechanical properties of cell walls and the levels of their components were investigated along intact wheat ( Triticum aestivum L.) Coleoptiles. Stress-relaxation analysis showed that the cell walls of stressed Coleoptiles were loosened as compared with those of unstressed ones not only in the apical but in the basal regions. The amounts of wall-bound ferulic acid (FA) and diferulic acid (DFA) of stressed Coleoptiles were substantially lower than those of unstressed ones in all regions. The cellulose and hemicellulose contents increased toward the coleoptile base. Osmotic stress reduced the cellulose content in the basal region but it slightly affected the hemicellulose content. The molecular weight of hemicellulose in the apical region of stressed Coleoptiles was higher than that of unstressed ones, while that in the basal region was almost the same in both Coleoptiles. FA, DFA and cellulose contents correlated with the cell wall mechanical property. The amount and molecular weight of hemicellulose, however, did not correlate. These results suggest that the reduced levels of FA and DFA in all regions and cellulose in the basal region of wheat Coleoptiles are involved in maintaining the cell wall extensibility under osmotic stress.

  • Osmotic Stress-Induced Growth Suppression of Dark-Grown Wheat (Triticum aestivum L.) Coleoptiles
    Plant and Cell Physiology, 1997
    Co-Authors: Kazuyuki Wakabayashi, Takayuki Hoson, Seiichiro Kamisaka
    Abstract:

    Application of 60 mM polyethylene glycol (PEG) to dark-grown wheat (Triticum aestivum L.) roots substantially reduced growth of Coleoptiles. However, when PEG was removed, the growth rate of these Coleoptiles greatly increased. Cell walls of stressed Coleoptiles remained loosened as compared with those of unstressed ones. The osmotic potential of the stressed Coleoptiles decreased to that of the 60 mM PEG solution. On the other hand, the extent of decrease in the osmotic potential of stressed roots was smaller than that of stressed Coleoptiles. The osmotic potential difference (An) between the cell sap and the incubation medium of stressed roots was substantially higher than that of unstressed ones. The amount of ink moved from roots, where it was applied, to the apical region of Coleoptiles was significantly reduced under osmotic stress conditions. When water was exogenously applied to abraded Coleoptiles, the growth of these stressed Coleoptiles was greatly promoted. These results suggest that inhibition of coleoptile growth under osmotic stress conditions is not directly related to a decrease in cell wall extensibility or to loss of the capacity to maintain osmotic potential gradients, but is caused by the reduction of the water supply from the roots to the Coleoptiles.

Takayuki Hoson - One of the best experts on this subject based on the ideXlab platform.

  • increase in the level of arabinoxylan hydroxycinnamate network in cell walls of wheat Coleoptiles grown under continuous hypergravity conditions
    Physiologia Plantarum, 2005
    Co-Authors: Kazuyuki Wakabayashi, Seiichiro Kamisaka, Kouichi Soga, Takayuki Hoson
    Abstract:

    Changes in the amount and composition of cell wall constituents in response to continuous hypergravity stimuli were studied in wheat (Triticum aestivum L.) Coleoptiles. The lengths of Coleoptiles grown under hypergravity (300 g) conditions for 2-4 days from germination stage were 60-70% of those of 1 g control. However, the net amounts of hemicellulosic polysaccharides and cellulose in hypergravity-treated Coleoptiles increased progressively as much as those in the control Coleoptiles. As a result, their contents per unit length of coleoptile largely increased under hypergravity conditions. In the hemicellulose fraction, the amounts of arabinose and xylose, the major components of the fraction, prominently increased in response to hypergravity. When hemicellulosic polysaccharides were separated into neutral and acidic polymers by an anion-exchange column, the amounts of the acidic fraction consisting of (glucurono)arabinoxylans were higher in hypergravity-treated Coleoptiles than in control Coleoptiles. The amounts of cell wall-bound ferulic acid and diferulic acid (DFA) increased dramatically in both 1 g control and hypergravity-treated Coleoptiles. Particularly, the amounts of DFA in hypergravity-treated Coleoptiles were significantly higher than those in control Coleoptiles during the incubation period. These results suggest that continuous hypergravity increases the rigid network structures via arabinoxylan-hydroxycinnamate cross-links within cell wall architecture in wheat Coleoptiles. These structures may have a load-bearing function and contribute to construct the stable cell wall against the gravitational force.

  • temperature modulates the cell wall mechanical properties of rice Coleoptiles by altering the molecular mass of hemicellulosic polysaccharides
    Physiologia Plantarum, 2003
    Co-Authors: Yukiko Nakamura, Kazuyuki Wakabayashi, Takayuki Hoson
    Abstract:

    The present study was conducted to investigate the mechanism inducing the difference in the cell wall extensibility of rice (Oryza sativa L. cv. Koshihikari) Coleoptiles grown under various temperature (10-50 degrees C) conditions. The growth rate and the cell wall extensibility of rice Coleoptiles exhibited the maximum value at 30-40 degrees C, and became smaller as the growth temperature rose or dropped from this temperature range. The amounts of cell wall polysaccharides per unit length of coleoptile increased in Coleoptiles grown at 40 degrees C, but not at other temperature conditions. On the other hand, the molecular size of hemicellulosic polysaccharides was small at temperatures where the cell wall extensibility was high (30-40 degrees C). The autolytic activities of cell walls obtained from Coleoptiles grown at 30 and 40 degrees C were substantially higher than those grown at 10, 20 and 50 degrees C. Furthermore, the activities of (1-->3),(1-->4)-beta-glucanases extracted from coleoptile cell walls showed a similar tendency. When oat (1-->3),(1-->4)-beta-glucans with high molecular mass were incubated with the cell wall enzyme preparations from Coleoptiles grown at various temperature conditions, the extensive molecular mass downshifts were brought about only by the cell wall enzymes obtained from Coleoptiles grown at 30-40 degrees C. There were close correlations between the cell wall extensibility and the molecular mass of hemicellulosic polysaccharides or the activity of beta -glucanases. These results suggest that the environmental temperature regulates the cell wall extensibility of rice Coleoptiles by modifying mainly the molecular mass of hemicellulosic polysaccharides. Modulation of the activity of beta-glucanases under various temperature conditions may be involved in the alteration of the molecular size of hemicellulosic polysaccharides.

  • Modification of cell wall architecture of wheat Coleoptiles grown under hypergravity conditions.
    Uchu Seibutsu Kagaku, 2003
    Co-Authors: Kazuyuki Wakabayashi, Seiichiro Kamisaka, Kouichi Soga, Takayuki Hoson
    Abstract:

    Cell wall structure of wheat Coleoptiles grown under continuous hypergravity (300 g) conditions was investigated. Length of Coleoptiles exposed to hypergravity for 2-4 days from germination stage was 60-70% of that of 1 g control. The amounts of cell wall polysaccharides substantially increased during the incubation period both in 1 g control and hypergravity-treated Coleoptiles. As a results, the levels of cell wall polysaccharides per unit length of coleoptile, which mean the thickness of cell walls, largely increased under hypergravity conditions. The major sugar components of the hemicellulose fraction, a polymer fraction extracted from cell walls with strong alkali, were arabinose (Ara), xylose (Xyl) and glucose (Glc). The molar ratios of Ara and Xyl to Glc in hypergravity-treated Coleoptiles were higher than those in control Coleoptiles. Furthermore, the fractionation of hemicellulosic polymers into the neutral and acidic polymers by the anion-exchange column showed that the levels of acidic polymers in cell walls of hypergravity-treated Coleoptiles were higher than those of control Coleoptiles. These results suggest that hypergravity stimuli bias the synthesis of hemicellulosic polysaccharides and increase the proportion of acidic polymers, such as arabinoxylans, in cell walls of wheat Coleoptiles. These structural changes in cell walls may contribute to plant resistance to hypergravity stimuli.

  • increased molecular mass of hemicellulosic polysaccharides is involved in growth inhibition of maize Coleoptiles and mesocotyls under hypergravity conditions
    Journal of Plant Research, 1999
    Co-Authors: Kouichi Soga, Takayuki Hoson, Kazuyuki Wakabayashi, Keita Harada, Seiichiro Kamisaka
    Abstract:

    mays L. cv. Cross Bantam T51) Coleoptiles and mesocotyls was suppressed by hypergravity at 30 g and above. Acceleration at 300 g significantly decreased the mechanical extensibility of cell walls of both organs. Hypergravity increased the amounts of hemicellulose and cellulose per unit length in mesocotyl walls, but not in coleoptile walls. The weight-average molecular masses of hemicellulosic polysaccharides were also increased by hypergravity in both organs. On the other hand, the activities of β-glucanases extracted from coleoptile and mesocotyl cell walls were decreased by hypergravity. These results suggest that the decreased activities of β-glucanases by hypergravity cause an increase in the molecular mass of hemicellulosic polysaccharides of both organs. The upshift of molecular mass of hemicellulosic polysaccharides as well as the thickening of cell walls under hypergravity conditions seems to be involved in making the cell wall mechanically rigid, thereby inhibiting elongation growth of maize Coleoptiles and mesocotyls.

  • Suppression of cell wall stiffening along Coleoptiles of wheat (Triticum aestivum L.) seedlings grown under osmotic stress conditions
    Journal of Plant Research, 1997
    Co-Authors: Kazuyuki Wakabayashi, Takayuki Hoson, Seiichiro Kamisaka
    Abstract:

    Effects of polyethylene glycol (PEG)-induced osmotic stress on the mechanical properties of cell walls and the levels of their components were investigated along intact wheat ( Triticum aestivum L.) Coleoptiles. Stress-relaxation analysis showed that the cell walls of stressed Coleoptiles were loosened as compared with those of unstressed ones not only in the apical but in the basal regions. The amounts of wall-bound ferulic acid (FA) and diferulic acid (DFA) of stressed Coleoptiles were substantially lower than those of unstressed ones in all regions. The cellulose and hemicellulose contents increased toward the coleoptile base. Osmotic stress reduced the cellulose content in the basal region but it slightly affected the hemicellulose content. The molecular weight of hemicellulose in the apical region of stressed Coleoptiles was higher than that of unstressed ones, while that in the basal region was almost the same in both Coleoptiles. FA, DFA and cellulose contents correlated with the cell wall mechanical property. The amount and molecular weight of hemicellulose, however, did not correlate. These results suggest that the reduced levels of FA and DFA in all regions and cellulose in the basal region of wheat Coleoptiles are involved in maintaining the cell wall extensibility under osmotic stress.

Moritoshi Iino - One of the best experts on this subject based on the ideXlab platform.

  • Circumnutation of rice Coleoptiles: its relationships with gravitropism and absence in lazy mutants.
    Plant Cell and Environment, 2006
    Co-Authors: Takeshi Yoshihara, Moritoshi Iino
    Abstract:

    Although circumnutation occurs widely in higher plants, its mechanism is little understood. The idea that circumnutation is based on gravitropism has long been investigated, but the reported results have been controversial. We used dark-grown Coleoptiles of rice (Oryza sativa L.) to re-investigate this issue. The following results supported the existence of a close relationship between gravitropism and circumnutation: (1) circumnutation disappears on a horizontal clinostat; (2) circumnutation is interrupted by a gravitropic response and re-initiated at a definable phase after gravitropic curvature; (3) circumnutation can be re-established by submergence and a brief gravitropic stimulation in the Coleoptiles that have stopped nutating in response to red light; and (4) lazy mutants show no circumnutation. In spite of these results, however, there were cases in which gravitropism and circumnutation could be separated. Firstly, the non-circumnutating lazy coleoptile showed nearly a wild-type level of gravitropic responsiveness in its upper half, although this part was an active site of both gravitropism and circumnutation in wild-type Coleoptiles. Secondly, Coleoptiles could nutate without overshooting the vertical when developing phototropic curvature. It is concluded that gravitropism influences, but it is not directly involved in the process of circumnutation. It is further suggested that a gravity signal, shared with gravitropism, contributes to the maintenance of circumnutation.

  • The Rice COLEOPTILE PHOTOTROPISM1 Gene Encoding an Ortholog of Arabidopsis NPH3 Is Required for Phototropism of Coleoptiles and Lateral Translocation of Auxin
    The Plant cell, 2004
    Co-Authors: Ken Haga, Ralf Neumann, Makoto Takano, Moritoshi Iino
    Abstract:

    We isolated a mutant, named coleoptile phototropism1 (cpt1), from γ-ray–mutagenized japonica-type rice (Oryza sativa). This mutant showed no coleoptile phototropism and severely reduced root phototropism after continuous stimulation. A map-based cloning strategy and transgenic complementation test were applied to demonstrate that a NPH3-like gene deleted in the mutant corresponds to CPT1. Phylogenetic analysis of putative CPT1 homologs of rice and related proteins indicated that CPT1 has an orthologous relationship with Arabidopsis thaliana NPH3. These results, along with those for Arabidopsis, demonstrate that NPH3/CPT1 is a key signal transduction component of higher plant phototropism. In an extended study with the cpt1 mutant, it was found that phototropic differential growth is accompanied by a CPT1-independent inhibition of net growth. Kinetic investigation further indicated that a small phototropism occurs in cpt1 Coleoptiles. This response, induced only transiently, was thought to be caused by the CPT1-independent growth inhibition. The 3H-indole-3-acetic acid applied to the coleoptile tip was asymmetrically distributed between the two sides of phototropically responding Coleoptiles. However, no asymmetry was induced in cpt1 Coleoptiles, indicating that lateral translocation of auxin occurs downstream of CPT1. It is concluded that the CPT1-dependent major phototropism of Coleoptiles is achieved by lateral auxin translocation and subsequent growth redistribution.

  • Photomorphogenesis of rice seedlings: a mutant impaired in phytochrome-mediated inhibition of coleoptile growth.
    Plant & cell physiology, 2003
    Co-Authors: Kamal K. Biswas, Ralf Neumann, Ken Haga, Osamu Yatoh, Moritoshi Iino
    Abstract:

    A mutant showing a long coleoptile phenotype under white light was isolated from gamma-ray-mutagenized rice (cv. Nihonmasari). This mutant, named cpm1 (coleoptile photomorphogenesis 1), has been found to be impaired in phytochrome-mediated inhibition of coleoptile growth. Another outstanding feature of the mutant is impaired anthesis. Under red light (R), cpm1 Coleoptiles elongate at a higher rate than wild-type (WT) Coleoptiles, owing to substantially reduced responsiveness to R. This phenotype occurs in an age-dependent manner, and cpm1 Coleoptiles become responsive to R as they elongate. The impairment was found in both very-low-fluence and low-fluence responses. Mutant Coleoptiles also elongate longer than WT Coleoptiles in darkness, but in this case the long coleoptile results from an extended elongation period. The cpm1 mutation does not affect the following phytochrome responses: the growth stimulation in submerged Coleoptiles (uncovered in this study), potentiation of greening, and down-regulation of PHYA transcription. The cpm1 mutation does not significantly affect the level of spectroscopically detectable phytochrome and the transcription levels of three phytochrome genes (PHYA-C). It is concluded that the CPM1 gene is involved in the phytochrome signal transduction that specifically leads to growth inhibition. Some aspects of rice seedling photomorphogenesis are discussed in relation to the results obtained.

  • Phytochrome is required for the occurrence of time‐dependent phototropism in maize Coleoptiles
    Plant cell & environment, 1996
    Co-Authors: Yujun Liu, Moritoshi Iino
    Abstract:

    Time-dependent phototropism (TDP), sometimes called second positive curvature, occurs when the duration of phototropic stimulation with blue light (B) exceeds a few minutes. TDP was characterized in maize (Zea mays L.) Coleoptiles raised under continuous red light (R). Subsequently, Coleoptiles adapted to darkness were used to investigate the effect of R on TDP. It was found that TDP, which is induced in R-grown Coleoptiles, does not occur in dark-adapted Coleoptiles and that dark-adapted Coleoptiles begin to show TDP after treatment with R. The TDP responsiveness became maximal 1-2 h after treatment with a R pulse and decreased during the next few hours. At least 10 min was required after a short pulse of R before the coleoptile began to respond to B for the induction of TDP. The effect of R in establishing the TDP responsiveness was totally suppressed by a pulse of far-red light given immediately after an inductive pulse of R. It is concluded that the mechanism of TDP requires for its establishment a R signal perceived by phytochrome. The TDP of R-grown and R-pretreated Coleoptiles showed relationships to stimulation times and fluence rates that are similar to those reported for oat Coleoptiles, except that TDP of maize showed a sharp increase in its magnitude within a narrow range of stimulation times as short as 5-10 min.

Kazuyuki Wakabayashi - One of the best experts on this subject based on the ideXlab platform.

  • increase in the level of arabinoxylan hydroxycinnamate network in cell walls of wheat Coleoptiles grown under continuous hypergravity conditions
    Physiologia Plantarum, 2005
    Co-Authors: Kazuyuki Wakabayashi, Seiichiro Kamisaka, Kouichi Soga, Takayuki Hoson
    Abstract:

    Changes in the amount and composition of cell wall constituents in response to continuous hypergravity stimuli were studied in wheat (Triticum aestivum L.) Coleoptiles. The lengths of Coleoptiles grown under hypergravity (300 g) conditions for 2-4 days from germination stage were 60-70% of those of 1 g control. However, the net amounts of hemicellulosic polysaccharides and cellulose in hypergravity-treated Coleoptiles increased progressively as much as those in the control Coleoptiles. As a result, their contents per unit length of coleoptile largely increased under hypergravity conditions. In the hemicellulose fraction, the amounts of arabinose and xylose, the major components of the fraction, prominently increased in response to hypergravity. When hemicellulosic polysaccharides were separated into neutral and acidic polymers by an anion-exchange column, the amounts of the acidic fraction consisting of (glucurono)arabinoxylans were higher in hypergravity-treated Coleoptiles than in control Coleoptiles. The amounts of cell wall-bound ferulic acid and diferulic acid (DFA) increased dramatically in both 1 g control and hypergravity-treated Coleoptiles. Particularly, the amounts of DFA in hypergravity-treated Coleoptiles were significantly higher than those in control Coleoptiles during the incubation period. These results suggest that continuous hypergravity increases the rigid network structures via arabinoxylan-hydroxycinnamate cross-links within cell wall architecture in wheat Coleoptiles. These structures may have a load-bearing function and contribute to construct the stable cell wall against the gravitational force.

  • temperature modulates the cell wall mechanical properties of rice Coleoptiles by altering the molecular mass of hemicellulosic polysaccharides
    Physiologia Plantarum, 2003
    Co-Authors: Yukiko Nakamura, Kazuyuki Wakabayashi, Takayuki Hoson
    Abstract:

    The present study was conducted to investigate the mechanism inducing the difference in the cell wall extensibility of rice (Oryza sativa L. cv. Koshihikari) Coleoptiles grown under various temperature (10-50 degrees C) conditions. The growth rate and the cell wall extensibility of rice Coleoptiles exhibited the maximum value at 30-40 degrees C, and became smaller as the growth temperature rose or dropped from this temperature range. The amounts of cell wall polysaccharides per unit length of coleoptile increased in Coleoptiles grown at 40 degrees C, but not at other temperature conditions. On the other hand, the molecular size of hemicellulosic polysaccharides was small at temperatures where the cell wall extensibility was high (30-40 degrees C). The autolytic activities of cell walls obtained from Coleoptiles grown at 30 and 40 degrees C were substantially higher than those grown at 10, 20 and 50 degrees C. Furthermore, the activities of (1-->3),(1-->4)-beta-glucanases extracted from coleoptile cell walls showed a similar tendency. When oat (1-->3),(1-->4)-beta-glucans with high molecular mass were incubated with the cell wall enzyme preparations from Coleoptiles grown at various temperature conditions, the extensive molecular mass downshifts were brought about only by the cell wall enzymes obtained from Coleoptiles grown at 30-40 degrees C. There were close correlations between the cell wall extensibility and the molecular mass of hemicellulosic polysaccharides or the activity of beta -glucanases. These results suggest that the environmental temperature regulates the cell wall extensibility of rice Coleoptiles by modifying mainly the molecular mass of hemicellulosic polysaccharides. Modulation of the activity of beta-glucanases under various temperature conditions may be involved in the alteration of the molecular size of hemicellulosic polysaccharides.

  • Modification of cell wall architecture of wheat Coleoptiles grown under hypergravity conditions.
    Uchu Seibutsu Kagaku, 2003
    Co-Authors: Kazuyuki Wakabayashi, Seiichiro Kamisaka, Kouichi Soga, Takayuki Hoson
    Abstract:

    Cell wall structure of wheat Coleoptiles grown under continuous hypergravity (300 g) conditions was investigated. Length of Coleoptiles exposed to hypergravity for 2-4 days from germination stage was 60-70% of that of 1 g control. The amounts of cell wall polysaccharides substantially increased during the incubation period both in 1 g control and hypergravity-treated Coleoptiles. As a results, the levels of cell wall polysaccharides per unit length of coleoptile, which mean the thickness of cell walls, largely increased under hypergravity conditions. The major sugar components of the hemicellulose fraction, a polymer fraction extracted from cell walls with strong alkali, were arabinose (Ara), xylose (Xyl) and glucose (Glc). The molar ratios of Ara and Xyl to Glc in hypergravity-treated Coleoptiles were higher than those in control Coleoptiles. Furthermore, the fractionation of hemicellulosic polymers into the neutral and acidic polymers by the anion-exchange column showed that the levels of acidic polymers in cell walls of hypergravity-treated Coleoptiles were higher than those of control Coleoptiles. These results suggest that hypergravity stimuli bias the synthesis of hemicellulosic polysaccharides and increase the proportion of acidic polymers, such as arabinoxylans, in cell walls of wheat Coleoptiles. These structural changes in cell walls may contribute to plant resistance to hypergravity stimuli.

  • increased molecular mass of hemicellulosic polysaccharides is involved in growth inhibition of maize Coleoptiles and mesocotyls under hypergravity conditions
    Journal of Plant Research, 1999
    Co-Authors: Kouichi Soga, Takayuki Hoson, Kazuyuki Wakabayashi, Keita Harada, Seiichiro Kamisaka
    Abstract:

    mays L. cv. Cross Bantam T51) Coleoptiles and mesocotyls was suppressed by hypergravity at 30 g and above. Acceleration at 300 g significantly decreased the mechanical extensibility of cell walls of both organs. Hypergravity increased the amounts of hemicellulose and cellulose per unit length in mesocotyl walls, but not in coleoptile walls. The weight-average molecular masses of hemicellulosic polysaccharides were also increased by hypergravity in both organs. On the other hand, the activities of β-glucanases extracted from coleoptile and mesocotyl cell walls were decreased by hypergravity. These results suggest that the decreased activities of β-glucanases by hypergravity cause an increase in the molecular mass of hemicellulosic polysaccharides of both organs. The upshift of molecular mass of hemicellulosic polysaccharides as well as the thickening of cell walls under hypergravity conditions seems to be involved in making the cell wall mechanically rigid, thereby inhibiting elongation growth of maize Coleoptiles and mesocotyls.

  • Suppression of cell wall stiffening along Coleoptiles of wheat (Triticum aestivum L.) seedlings grown under osmotic stress conditions
    Journal of Plant Research, 1997
    Co-Authors: Kazuyuki Wakabayashi, Takayuki Hoson, Seiichiro Kamisaka
    Abstract:

    Effects of polyethylene glycol (PEG)-induced osmotic stress on the mechanical properties of cell walls and the levels of their components were investigated along intact wheat ( Triticum aestivum L.) Coleoptiles. Stress-relaxation analysis showed that the cell walls of stressed Coleoptiles were loosened as compared with those of unstressed ones not only in the apical but in the basal regions. The amounts of wall-bound ferulic acid (FA) and diferulic acid (DFA) of stressed Coleoptiles were substantially lower than those of unstressed ones in all regions. The cellulose and hemicellulose contents increased toward the coleoptile base. Osmotic stress reduced the cellulose content in the basal region but it slightly affected the hemicellulose content. The molecular weight of hemicellulose in the apical region of stressed Coleoptiles was higher than that of unstressed ones, while that in the basal region was almost the same in both Coleoptiles. FA, DFA and cellulose contents correlated with the cell wall mechanical property. The amount and molecular weight of hemicellulose, however, did not correlate. These results suggest that the reduced levels of FA and DFA in all regions and cellulose in the basal region of wheat Coleoptiles are involved in maintaining the cell wall extensibility under osmotic stress.

Yawhuei Lin - One of the best experts on this subject based on the ideXlab platform.

  • changes in soluble and cell wall bound peroxidase activities with growth in anoxia treated rice oryza sativa l Coleoptiles and roots
    Plant Science, 1995
    Co-Authors: Tsemin Lee, Yawhuei Lin
    Abstract:

    Abstract The activity of soluble and cell wall-bound (1.0 M NaCl extractable) peroxidase in relation to growth of anoxia-grown Indica rice seedlings (Oryza sativa L. cv. Taichung Native 1) was examined. Guaiacol and syringaldazine were used to assay for peroxidase activity. In air-grown Coleoptiles, guaiacol or syringaldazine peroxidase activity initially decreased or remained constant, respectively, in the early period but then both increased as coleoptile elongation ceased. In air-grown roots, both guaiacol and syringaldazine peroxidase activities decreased slightly during the growth period. In response to anoxia, coleoptile elongation was stimulated but root growth was seriously inhibited. Anoxia induced a significant decrease in activity of cell wall-bound guaiacol and syringaldazine peroxidase while soluble peroxidase activity was not affected in Coleoptiles. In contrast to coleptiles, anoxia-grown roots showed an increase in cell wall-bound guaiacol and syringaldazine peroxidase activities. When transferred to aerobic conditions, cell wall-bound guaiacol and syringaldazine peroxidase activities in anoxia-grown Coleoptiles and roots recovered almost to the air-control levels. On exposure to ABA, the enhancement of coleoptile elongation and the decrease of cell wall-bound peroxidase activity in anoxia-grown Coleoptiles were inhibited. These results indicate that there is a reciprocal correlation between growth and cell wall-bound peroxidase levels in etiolated rice seedlings.

  • trypsin inhibitor and trypsin like protease activity in air or submergence grown rice oryza sativa l Coleoptiles
    Plant Science, 1995
    Co-Authors: Tsemin Lee, Yawhuei Lin
    Abstract:

    Abstract Changes of trypsin inhibitor (TI) and trypsin-like protease activities of rice (Oryza sativa L.) Coleoptiles grown under air or submergence conditions were investigated. Activity staining of TIs on a 15% SDS-PAGE gel showed that there were two TI bands (33.6 and 21.4 kDa) in Tainung 67 (TNG.67, a Japonica cultivar) and three bands (33.6, 21.4 and 12.8 kDa) in Taichung Native 1 (TN.1, an Indica cultivar). Each TNG.67 or TN.1 TI that was eluted from SDS-PAGE gels could inhibit trypsin-like proteinase activity in coleoptile crude extract. In air-grown Coleoptiles. TI activity determined by the inhibition of trypsin-catalyzed casein or Nα-benzoyl- l -arginine-4-nitroanilide (Bz- l -Arg-4-NA) hydrolysis decreased 6 days after imbibition; and strength of TI bands on SDS-PAGE gels also decreased 7 days after imbibition. In contrast, proteinase activity determined by casein hydrolysis and trypsin-like protease activity determined by Bz- l -Arg-4-NA hydrolysis both reached maxima 6 days after imbibition in air-grown Coleoptiles. Soluble protein contents in air-grown Coleoptiles decreased but free amino acid contents increased 7 days after imbibition. When seedlings at 3 days after imbibition were exposed to submergence for 2 days, TI activity and strength of TI bands decreased. Soluble protein contents in submergence-grown Coleoptiles also decreased but free amino acid contents increased. These submergence effects were inhibited by 10−6 M ABA.