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Takayuki Hoson - One of the best experts on this subject based on the ideXlab platform.
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Effects of gravistimuli on osmoregulation in azuki bean Epicotyls
Advances in Space Research, 2013Co-Authors: Yan Zhang, Kazuyuki Wakabayashi, Kouichi Soga, Takayuki HosonAbstract:Abstract The effects of hypergravity on growth and osmoregulation were examined in dark-grown azuki bean Epicotyls. Elongation growth of Epicotyls was promptly suppressed by hypergravity at 300 g . On the contrary, the increase in fresh weight of Epicotyls during incubation was not suppressed by hypergravity at 300 g at least up to 6 h. Also, the level of total osmotic solutes increased during epicotyl growth for 6 h, which was not affected by hypergravity. These results suggest that azuki bean Epicotyls are capable of maintaining osmoregulation even under 300 g conditions for a short period. On the other hand, the increase in fresh weight of Epicotyls was suppressed, in addition to suppression of elongation growth, when seedlings were treated with 300 g for 24 h. The increase in level of total osmotic solutes was also inhibited by 24 h hypergravity treatment, which was accounted by the reduced levels of organic solutes, such as sugars and amino acids. Furthermore, the dry weight of seeds decreased during incubation for 24 h, but the decrease was inhibited by hypergravity at 300 g . Hypergravity treatment at 300 g for 24 h also increased the pH value of apoplastic solution in Epicotyls. Taken together, these results suggest that the translocation of organic solutes from the seed to Epicotyls is inhibited by prolonged hypergravity treatment, which may underlie the suppression of epicotyl growth, and that the breakdown of H + gradient across the plasma membrane in epicotyl cells may be at least partly involved in the reduction of organic solute accumulation under hypergravity conditions.
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Fucosylated high molecular mass but not non-fucosylated low molecular mass xyloglucans undergo an extensive depolymerization in cell walls of azuki bean Epicotyls
Journal of Plant Physiology, 2010Co-Authors: Kuninori Arai, Kazuyuki Wakabayashi, Kouichi Soga, Takayuki HosonAbstract:Abstract Epicotyl cuttings of azuki bean were incubated with [ 14 C]-glucose (Glc) or [ 3 H]-fucose (Fuc), and the metabolism of radiolabeled polymers in the 24% KOH-extractable cell wall fraction was investigated. Applied 14 C-Glc and 3 H-Fuc were predominantly incorporated into the glucan backbone and Fuc residue of xyloglucan molecules, respectively. On gel permeation chromatography, 14 C-polymers consisted of a main peak (0.7–1.0 MDa) and shoulder peak (30 kDa). The pattern was similar to that of iodine-reactive xyloglucans in the fraction. On the other hand, 3 H-polymers consisted of a single peak eluted around 0.7–1.0 MDa. The elution patterns of 14 C- and 3 H-polymers were constant during the incubation period, although incorporated radioactivity increased with time. In the pulse-chase experiment, the high molecular mass peaks (0.7–1.0 MDa) of both 14 C- and 3 H-polymers showed an extensive molecular mass downshift, but not the shoulder peak of 14 C-polymers. These results indicate that xyloglucans in the fraction consist of two types of molecules; fucosylated high molecular mass polymers and non-fucosylated low molecular mass polymers. Azuki bean Epicotyls may synthesize both types of xyloglucans independently, but only fucosylated xyloglucans undergo an active depolymerization in the cell wall.
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Cell wall-bound peroxidase activity and lignin formation in azuki bean Epicotyls grown under hypergravity conditions.
Journal of Plant Physiology, 2009Co-Authors: Kazuyuki Wakabayashi, Kouichi Soga, Saho Nakano, Takayuki HosonAbstract:Summary The effects of accelerated gravity stimuli on the cell wall-bound peroxidase activity and the lignin content were investigated along Epicotyls of azuki bean ( Vigna angularis ) seedlings. The endogenous growth occurred primarily in the upper regions of the epicotyl, but no growth was detected in the middle or basal regions. Hypergravity treatment at 300 g for 6 h suppressed elongation growth and stimulated lateral expansion of the upper regions. The content of acetyl bromide-soluble lignin increased gradually from the apical to the basal regions of Epicotyls. Hypergravity treatment stimulated the increase in the lignin content in Epicotyls, particularly in the middle and basal regions. The peroxidase activity in the protein fraction extracted with a high ionic strength buffer from the cell wall preparation also increased gradually toward the basal region, and hypergravity treatment increased the activity in all epicotyl regions. There was a close correlation between the lignin content and the enzyme activity. These results suggest that hypergravity increases the activity of cell wall-bound peroxidase followed by increases of the lignin formation in epicotyl cell walls, which may contribute to increasing the rigidity of cell walls against the gravitational force.
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Role of xyloglucan in gravitropic bending of azuki bean epicotyl.
Physiologia Plantarum, 2008Co-Authors: Toshimitsu Ikushima, Kouichi Soga, Takayuki Hoson, Teruo ShimmenAbstract:The mechanism of the gravitropic bending was studied in azuki bean Epicotyls. The cell wall extensibility of the lower side became higher than that of the upper side in the epicotyl bending upward. The contents of matrix polysaccharides of the cell wall (pectin and xyloglucan in hemicellulose-II) in the lower side became smaller than those in the upper side. The molecular mass of xyloglucans in the lower side decreased. After an epicotyl was fixed to a metal rod to prevent the bending, gravistimulation was applied. Fundamentally the same results were obtained with respect to rheological and chemical characteristics of the cell wall as those of Epicotyls showing gravitropic bending. The present results suggested that the initial gravitropic bending was caused by the increase in extensibility of the lower side and the decrease in extensibility of the upper side via the change of the cell wall matrix, especially xyloglucans.
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different cell wall polysaccharides are responsible for gravity resistance in the upper and the basal regions of azuki bean Epicotyls
Biological Sciences in Space, 2007Co-Authors: Saho Nakano, Kazuyuki Wakabayashi, Kouichi Soga, Takayuki HosonAbstract:Effects of hypergravity on growth and the levels of cell wall polysaccharides were examined along Epicotyls of dark-grown azuki bean (Vigna angularis Ohwi et Ohashi cv. Erimowase). Elongation growth occurred only in the upper regions, which was suppressed by hypergravity at 300 G. The fresh weight also increased in the upper regions, but hypergravity increased it only slightly in the basal regions. The thickness of Epicotyls was increased clearly in the upper regions and slightly in the basal regions by hypergravity. The levels of pectin, hemicellulose-I, and hemicellulose-II per unit length of epicotyl were increased by hypergravity in the upper regions, but not in the basal ones. Also, the levels of xyloglucans were increased by hypergravity only in the upper regions. On the other hand, the levels of cellulose per unit length increased from the apical to the basal regions, and hypergravity further increased the levels in all regions. These results suggest that cellulose, instead of xyloglucans, acts as anti-gravitational polysaccharides in the basal regions. Cellulose and xyloglucans may cooperate in resistance of whole stem organs to the gravitational force.
Béla Böddi - One of the best experts on this subject based on the ideXlab platform.
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distinct uv a or uv b irradiation induces protochlorophyllide photoreduction and bleaching in dark grown pea pisum sativum l Epicotyls
Photosynthesis Research, 2019Co-Authors: Annamaria Kosa, Anna Laura Erdei, Béla BöddiAbstract:The effects of distinct UV-A and UV-B radiations were studied on etiolated pea (Pisum sativum L.) Epicotyls. Emission spectra of the native protochlorophyll and protochlorophyllide forms were measured when Epicotyls were excited with 360 or 300 nm light. The UV-A (360 nm) excited mainly the non-enzyme-bound monomers of protochlorophyll and protochlorophyllide and the UV-B (300 nm) excited preferentially the flash-photoactive protochlorophyllide complexes. These latter complexes converted into short- and long-wavelength chlorophyllide forms at 10-s illumination with both wavelength irradiations. As the spectral changes were very small, the effects of longer illumination periods were studied. Room temperature fluorescence emission spectra were measured from the same epicotyl spots before and after irradiation with various wavelengths between 280 and 360 nm for 15 min and the “illuminated” minus “dark” difference spectra were calculated. Both the UV-A and the UV-B irradiations caused photoreduction of protochlorophyllide into chlorophyllide. At 10 µmol photons m−2 s−1, the photoreduction rates were similar, however, at 60 µmol photons m−2 s−1, the UV-B irradiation was more effective in inducing chlorophyllide formation than the UV-A. The action spectra of protochlorophyllide plus protochlorophyll loss and chlorophyllide production showed that the radiation around 290 nm was the most effective in provoking protochlorophyllide photoreduction and the UV light above 320 nm caused strong bleaching. These results show that the effect of the UV radiation should be considered when discussing the protochlorophyllide–chlorophyllide photoreduction during germination and as a part of the regeneration of the photosynthetic apparatus proceeding in the daily run of photosynthesis.
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delayed chlorophyll accumulation and pigment photodestruction in the Epicotyls of dark grown pea pisum sativum
Physiologia Plantarum, 2005Co-Authors: Béla Böddi, Roland Loudeche, Fabrice FranckAbstract:A comparison was performed of the tetrapyrrole transformations that occur upon irradiation of epicotyl or leaves of dark-grown Pisum sativum L. (var. Zsuzsi, Hungary). High performance liquid chromatography analysis after continuous or flash-irradiation showed that the biosynthetic pathway from protochlorophyllide (Pchlide) to chlorophyll (Chl) a was markedly slowed down at the step of the reduction of geranylgeranyl(gg)-Chl to dihydrogeranylgeranyl (dhgg)-Chl in Epicotyls, whereas phytyl-Chl was synthesized in leaves subjected to the same light treatments. Quantitative pigment analysis during continuous irradiations of different intensities also showed that significant Pchlide photodestruction occurred in Epicotyls even under weak light. When both Pchlide and chlorophyllide and/or chlorophylls were present in Epicotyls, Pchlide photodestruction was faster under 630-nm light than under 670-nm light, which indicates that this process is most efficiently promoted by Pchlide excitation. Pre-incubation of epicotyl segments with 10 mM ascorbate partly alleviated pigment photodestruction in white light. It is concluded that formation of photoactive Pchlide-Pchlide oxidoreductase complexes is important to prevent fast pigment photooxidation after Pchlide accumulation in the dark.
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Light-induced wilting and its molecular mechanism in Epicotyls of dark-germinated pea (Pisum sativum L.) seedlings.
Plant and Cell Physiology, 2005Co-Authors: Noémi Erdei, Csengele Barta, Éva Hideg, Béla BöddiAbstract:Possible mechanisms behind the light-induced wilting of dark-germinated pea (Pisum sativum L.) Epicotyls were studied. Illumination with photosynthetically active radiation caused a fast turgor loss and wilting in the middle segments of the Epicotyls accompanied by accumulation of water in the intercellular cavities. During this process, room temperature fluorescence emission spectra showed gradual bleaching of porphyrin-type pigments, which was lessened by incubating the Epicotyls with excess ascorbate before illumination. Detection of singlet oxygen and lipid peroxidation products in the illuminated Epicotyls suggested the occurrence of porphyrin-photosenzitized membrane damage as a cause of disordered water status and sequential wilting.
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Delayed chlorophyll accumulation and pigment photodestruction in the Epicotyls of dark‐grown pea (Pisum sativum)
Physiologia Plantarum, 2005Co-Authors: Béla Böddi, Roland Loudeche, Fabrice FranckAbstract:A comparison was performed of the tetrapyrrole transformations that occur upon irradiation of epicotyl or leaves of dark-grown Pisum sativum L. (var. Zsuzsi, Hungary). High performance liquid chromatography analysis after continuous or flash-irradiation showed that the biosynthetic pathway from protochlorophyllide (Pchlide) to chlorophyll (Chl) a was markedly slowed down at the step of the reduction of geranylgeranyl(gg)-Chl to dihydrogeranylgeranyl (dhgg)-Chl in Epicotyls, whereas phytyl-Chl was synthesized in leaves subjected to the same light treatments. Quantitative pigment analysis during continuous irradiations of different intensities also showed that significant Pchlide photodestruction occurred in Epicotyls even under weak light. When both Pchlide and chlorophyllide and/or chlorophylls were present in Epicotyls, Pchlide photodestruction was faster under 630-nm light than under 670-nm light, which indicates that this process is most efficiently promoted by Pchlide excitation. Pre-incubation of epicotyl segments with 10 mM ascorbate partly alleviated pigment photodestruction in white light. It is concluded that formation of photoactive Pchlide-Pchlide oxidoreductase complexes is important to prevent fast pigment photooxidation after Pchlide accumulation in the dark.
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the two spectroscopically different short wavelength protochlorophyllide forms in pea Epicotyls are both monomeric
Biochimica et Biophysica Acta, 1998Co-Authors: Béla Böddi, Katalin Kispetik, Andras D Kaposi, Judit Fidy, Christer SundqvistAbstract:Abstract The spectral properties of the protochlorophyllide forms in the Epicotyls of dark-grown pea seedlings have been studied in a temperature range, from 10 to 293 K with conventional fluorescence emission and excitation spectroscopy as well as by fluorescence line narrowing (FLN) at cryogenic temperatures. The conventional fluorescence techniques at lower temperatures revealed separate bands at 628, 634–636, 644 and 655 nm. At room temperature (293 K) the 628 and 634–636 nm emission bands strongly overlapped and the band shape was almost independent of the excitation wavelength. Under FLN conditions, vibronically resolved fluorescence spectra could be measured for the 628 and 634–636 nm bands. The high resolution of this technique excluded the excitonic nature of respective excited states and made it possible to determine the pure electronic (0,0) range of the spectra of the two components. Thus it was concluded that the 628 and 634–636 nm (0,0) emission bands originate from two monomeric forms of protochlorophyllide and the spectral difference is interpreted as a consequence of environmental effects of the surrounding matrix. On the basis of earlier results and the data presented here, a model is discussed in which the 636 nm form is considered as an enzyme-bound protochlorophyllide and the 628 nm form as a protochlorophyllide pool from which the substrate is replaced when the epicotyl is illuminated with continuous light.
Christer Sundqvist - One of the best experts on this subject based on the ideXlab platform.
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the two spectroscopically different short wavelength protochlorophyllide forms in pea Epicotyls are both monomeric
Biochimica et Biophysica Acta, 1998Co-Authors: Béla Böddi, Katalin Kispetik, Andras D Kaposi, Judit Fidy, Christer SundqvistAbstract:Abstract The spectral properties of the protochlorophyllide forms in the Epicotyls of dark-grown pea seedlings have been studied in a temperature range, from 10 to 293 K with conventional fluorescence emission and excitation spectroscopy as well as by fluorescence line narrowing (FLN) at cryogenic temperatures. The conventional fluorescence techniques at lower temperatures revealed separate bands at 628, 634–636, 644 and 655 nm. At room temperature (293 K) the 628 and 634–636 nm emission bands strongly overlapped and the band shape was almost independent of the excitation wavelength. Under FLN conditions, vibronically resolved fluorescence spectra could be measured for the 628 and 634–636 nm bands. The high resolution of this technique excluded the excitonic nature of respective excited states and made it possible to determine the pure electronic (0,0) range of the spectra of the two components. Thus it was concluded that the 628 and 634–636 nm (0,0) emission bands originate from two monomeric forms of protochlorophyllide and the spectral difference is interpreted as a consequence of environmental effects of the surrounding matrix. On the basis of earlier results and the data presented here, a model is discussed in which the 636 nm form is considered as an enzyme-bound protochlorophyllide and the 628 nm form as a protochlorophyllide pool from which the substrate is replaced when the epicotyl is illuminated with continuous light.
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Protochlorophyllide transformations and chlorophyll accumulation in Epicotyls of pea (Pisum sativum)
Physiologia Plantarum, 1996Co-Authors: Béla Böddi, Margareta Ryberg, Ivar Evertsson, Christer SundqvistAbstract:Low-temperature fluorescence emission spectra of Epicotyls of 6.5-day-old dark-grown seedlings of pea (Pisum sativum L.) showed the dominance of short-wavelength protoch lorophyllide forms with emission maxima at 629 and 636 nm, respectively. The presence of long-wavelength protochlorophyllide with emission maxima around 650 nm was just detectable. Accordingly, irradiation with millisecond flashes gave a minute formation of chlorophyllide. The chlorophyll(ide) formation varied along the epicotyl. Irradiation with continuous light for 1.5 h resulted in an evident accumulation of chlorophyll(ide) in the upper part of the epicotyl. Only small amounts accumulated in the middle section. The conversion of protochlorophyllide to chlorophyllide was temperature dependent and almost arrested at 0°C. The chlorophyll(ide) formed had one dominating fluorescence peak at 681 nm. Irradiation for 24 h gave almost 100 times more chlorophyll in the upper part of the epicotyl than in the lower part. Electron micrographs from the upper part of the epicotyl irradiated for 6 h showed plastids with several developing thylakoids, while the plastids in the lower part of the epicotyl had only a few thylakoids. The dominance of short-wavelength protochlorophyllide forms indicated the presence of protochlorophyllide not bound to the active site of NADPH-protochlorophyllide oxidoreductase (EC 1.3.1.33). The inability of the short-wavelength form to transform into chlorophyllide with flash light denotes a dislocation from the active site. The time and temperature dependence of the chlorophyll(ide) formation in continuous light indicates that a relocation is required of the short-wavelength protochlorophyllide before chlorophyllide formation can occur.
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protochlorophyllide forms in non greening Epicotyls of dark grown pea pisum sativum
Physiologia Plantarum, 1994Co-Authors: Béla Böddi, Birgitta Mcewen, Margareta Ryberg, Christer SundqvistAbstract:Low-temperature fluorescence emission spectra of 6.5-day-old dark-grown Epicotyls of pea (Pisum sativum) revealed the presence of protochlorophyll(ide). The upper part of the epicotyl contained 30% of the protochlorophyll(ide) content per fresh weight found in pea leaves, whereas the lower part contained 3%. Three discrete spectral forms of protochlorophyll(ide) were clearly distinguished after Gaussian deconvolution of fluorescence excitation and emission spectra. Adding the satellite bands of the Qy(0-0) transitions (the emission vibrational (Emv) bands with correlated amplitudes, gave the following delineation: Ex439–Em629–Emv684, Ex447–Em636–Emv700 and Ex456–Em650–Emv728. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) followed by immunodetection of whole tissue extracts of the epicotyl indicated the presence of NADPH-protochlorophyllide oxidoreductase (EC 1.3.1.33). Electron micrographs showed prolamellar bodies in at most 11 % of the plastid profiles of the epicotyl cells. These prolamellar bodies were smaller, and many of them showed less regular structure than those of the leaves. Taken together, the results indicate that the protochlorophyll(ide) in Epicotyls is arranged in a different way than in leaves.
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Protochlorophyllide forms in non‐greening Epicotyls of dark‐grown pea (Pisum sativum)
Physiologia Plantarum, 1994Co-Authors: Béla Böddi, Birgitta Mcewen, Margareta Ryberg, Christer SundqvistAbstract:Low-temperature fluorescence emission spectra of 6.5-day-old dark-grown Epicotyls of pea (Pisum sativum) revealed the presence of protochlorophyll(ide). The upper part of the epicotyl contained 30% of the protochlorophyll(ide) content per fresh weight found in pea leaves, whereas the lower part contained 3%. Three discrete spectral forms of protochlorophyll(ide) were clearly distinguished after Gaussian deconvolution of fluorescence excitation and emission spectra. Adding the satellite bands of the Qy(0-0) transitions (the emission vibrational (Emv) bands with correlated amplitudes, gave the following delineation: Ex439–Em629–Emv684, Ex447–Em636–Emv700 and Ex456–Em650–Emv728. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) followed by immunodetection of whole tissue extracts of the epicotyl indicated the presence of NADPH-protochlorophyllide oxidoreductase (EC 1.3.1.33). Electron micrographs showed prolamellar bodies in at most 11 % of the plastid profiles of the epicotyl cells. These prolamellar bodies were smaller, and many of them showed less regular structure than those of the leaves. Taken together, the results indicate that the protochlorophyll(ide) in Epicotyls is arranged in a different way than in leaves.
Kazuyuki Wakabayashi - One of the best experts on this subject based on the ideXlab platform.
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Effects of gravistimuli on osmoregulation in azuki bean Epicotyls
Advances in Space Research, 2013Co-Authors: Yan Zhang, Kazuyuki Wakabayashi, Kouichi Soga, Takayuki HosonAbstract:Abstract The effects of hypergravity on growth and osmoregulation were examined in dark-grown azuki bean Epicotyls. Elongation growth of Epicotyls was promptly suppressed by hypergravity at 300 g . On the contrary, the increase in fresh weight of Epicotyls during incubation was not suppressed by hypergravity at 300 g at least up to 6 h. Also, the level of total osmotic solutes increased during epicotyl growth for 6 h, which was not affected by hypergravity. These results suggest that azuki bean Epicotyls are capable of maintaining osmoregulation even under 300 g conditions for a short period. On the other hand, the increase in fresh weight of Epicotyls was suppressed, in addition to suppression of elongation growth, when seedlings were treated with 300 g for 24 h. The increase in level of total osmotic solutes was also inhibited by 24 h hypergravity treatment, which was accounted by the reduced levels of organic solutes, such as sugars and amino acids. Furthermore, the dry weight of seeds decreased during incubation for 24 h, but the decrease was inhibited by hypergravity at 300 g . Hypergravity treatment at 300 g for 24 h also increased the pH value of apoplastic solution in Epicotyls. Taken together, these results suggest that the translocation of organic solutes from the seed to Epicotyls is inhibited by prolonged hypergravity treatment, which may underlie the suppression of epicotyl growth, and that the breakdown of H + gradient across the plasma membrane in epicotyl cells may be at least partly involved in the reduction of organic solute accumulation under hypergravity conditions.
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Fucosylated high molecular mass but not non-fucosylated low molecular mass xyloglucans undergo an extensive depolymerization in cell walls of azuki bean Epicotyls
Journal of Plant Physiology, 2010Co-Authors: Kuninori Arai, Kazuyuki Wakabayashi, Kouichi Soga, Takayuki HosonAbstract:Abstract Epicotyl cuttings of azuki bean were incubated with [ 14 C]-glucose (Glc) or [ 3 H]-fucose (Fuc), and the metabolism of radiolabeled polymers in the 24% KOH-extractable cell wall fraction was investigated. Applied 14 C-Glc and 3 H-Fuc were predominantly incorporated into the glucan backbone and Fuc residue of xyloglucan molecules, respectively. On gel permeation chromatography, 14 C-polymers consisted of a main peak (0.7–1.0 MDa) and shoulder peak (30 kDa). The pattern was similar to that of iodine-reactive xyloglucans in the fraction. On the other hand, 3 H-polymers consisted of a single peak eluted around 0.7–1.0 MDa. The elution patterns of 14 C- and 3 H-polymers were constant during the incubation period, although incorporated radioactivity increased with time. In the pulse-chase experiment, the high molecular mass peaks (0.7–1.0 MDa) of both 14 C- and 3 H-polymers showed an extensive molecular mass downshift, but not the shoulder peak of 14 C-polymers. These results indicate that xyloglucans in the fraction consist of two types of molecules; fucosylated high molecular mass polymers and non-fucosylated low molecular mass polymers. Azuki bean Epicotyls may synthesize both types of xyloglucans independently, but only fucosylated xyloglucans undergo an active depolymerization in the cell wall.
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Cell wall-bound peroxidase activity and lignin formation in azuki bean Epicotyls grown under hypergravity conditions.
Journal of Plant Physiology, 2009Co-Authors: Kazuyuki Wakabayashi, Kouichi Soga, Saho Nakano, Takayuki HosonAbstract:Summary The effects of accelerated gravity stimuli on the cell wall-bound peroxidase activity and the lignin content were investigated along Epicotyls of azuki bean ( Vigna angularis ) seedlings. The endogenous growth occurred primarily in the upper regions of the epicotyl, but no growth was detected in the middle or basal regions. Hypergravity treatment at 300 g for 6 h suppressed elongation growth and stimulated lateral expansion of the upper regions. The content of acetyl bromide-soluble lignin increased gradually from the apical to the basal regions of Epicotyls. Hypergravity treatment stimulated the increase in the lignin content in Epicotyls, particularly in the middle and basal regions. The peroxidase activity in the protein fraction extracted with a high ionic strength buffer from the cell wall preparation also increased gradually toward the basal region, and hypergravity treatment increased the activity in all epicotyl regions. There was a close correlation between the lignin content and the enzyme activity. These results suggest that hypergravity increases the activity of cell wall-bound peroxidase followed by increases of the lignin formation in epicotyl cell walls, which may contribute to increasing the rigidity of cell walls against the gravitational force.
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different cell wall polysaccharides are responsible for gravity resistance in the upper and the basal regions of azuki bean Epicotyls
Biological Sciences in Space, 2007Co-Authors: Saho Nakano, Kazuyuki Wakabayashi, Kouichi Soga, Takayuki HosonAbstract:Effects of hypergravity on growth and the levels of cell wall polysaccharides were examined along Epicotyls of dark-grown azuki bean (Vigna angularis Ohwi et Ohashi cv. Erimowase). Elongation growth occurred only in the upper regions, which was suppressed by hypergravity at 300 G. The fresh weight also increased in the upper regions, but hypergravity increased it only slightly in the basal regions. The thickness of Epicotyls was increased clearly in the upper regions and slightly in the basal regions by hypergravity. The levels of pectin, hemicellulose-I, and hemicellulose-II per unit length of epicotyl were increased by hypergravity in the upper regions, but not in the basal ones. Also, the levels of xyloglucans were increased by hypergravity only in the upper regions. On the other hand, the levels of cellulose per unit length increased from the apical to the basal regions, and hypergravity further increased the levels in all regions. These results suggest that cellulose, instead of xyloglucans, acts as anti-gravitational polysaccharides in the basal regions. Cellulose and xyloglucans may cooperate in resistance of whole stem organs to the gravitational force.
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changes in membrane lipid composition in azuki bean Epicotyls under hypergravity conditions possible role of membrane sterols in gravity resistance
Advances in Space Research, 2007Co-Authors: T Koizumi, Kazuyuki Wakabayashi, Kouichi Soga, T Sakaki, S Usui, Takayuki HosonAbstract:Abstract Seedlings of azuki bean ( Vigna angularis Ohwi et Ohashi) were cultivated under hypergravity conditions, and changes in membrane lipid composition in their Epicotyls were analyzed. Under hypergravity conditions at 300 g , the levels of total sterols, phospholipids, and fatty acids per fresh weight were kept higher, as compared with 1 g controls. In particular, sterol levels were prominently increased by hypergravity. On the other hand, hypergravity did not clearly influence the levels of each phospholipid and glycolipid class, or their fatty acid compositions. Thus, the effect of hypergravity on membrane lipid metabolism was specific for sterol biosynthesis. In various regions of azuki Epicotyls, high growth rate was associated with high sterol levels. Hypergravity suppressed elongation growth and stimulated lateral expansion of azuki Epicotyls. In the presence of lovastatin, an inhibitor of sterol biosynthesis, at 30 μM, such changes in growth parameters occurred even under 1 g conditions, suggesting that lovastatin made Epicotyls hypersensitive to the gravitational force. These results support the hypothesis that membrane sterols are involved in maintenance of normal growth capacity of plant organs against gravity.
Fabrice Franck - One of the best experts on this subject based on the ideXlab platform.
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delayed chlorophyll accumulation and pigment photodestruction in the Epicotyls of dark grown pea pisum sativum
Physiologia Plantarum, 2005Co-Authors: Béla Böddi, Roland Loudeche, Fabrice FranckAbstract:A comparison was performed of the tetrapyrrole transformations that occur upon irradiation of epicotyl or leaves of dark-grown Pisum sativum L. (var. Zsuzsi, Hungary). High performance liquid chromatography analysis after continuous or flash-irradiation showed that the biosynthetic pathway from protochlorophyllide (Pchlide) to chlorophyll (Chl) a was markedly slowed down at the step of the reduction of geranylgeranyl(gg)-Chl to dihydrogeranylgeranyl (dhgg)-Chl in Epicotyls, whereas phytyl-Chl was synthesized in leaves subjected to the same light treatments. Quantitative pigment analysis during continuous irradiations of different intensities also showed that significant Pchlide photodestruction occurred in Epicotyls even under weak light. When both Pchlide and chlorophyllide and/or chlorophylls were present in Epicotyls, Pchlide photodestruction was faster under 630-nm light than under 670-nm light, which indicates that this process is most efficiently promoted by Pchlide excitation. Pre-incubation of epicotyl segments with 10 mM ascorbate partly alleviated pigment photodestruction in white light. It is concluded that formation of photoactive Pchlide-Pchlide oxidoreductase complexes is important to prevent fast pigment photooxidation after Pchlide accumulation in the dark.
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Delayed chlorophyll accumulation and pigment photodestruction in the Epicotyls of dark‐grown pea (Pisum sativum)
Physiologia Plantarum, 2005Co-Authors: Béla Böddi, Roland Loudeche, Fabrice FranckAbstract:A comparison was performed of the tetrapyrrole transformations that occur upon irradiation of epicotyl or leaves of dark-grown Pisum sativum L. (var. Zsuzsi, Hungary). High performance liquid chromatography analysis after continuous or flash-irradiation showed that the biosynthetic pathway from protochlorophyllide (Pchlide) to chlorophyll (Chl) a was markedly slowed down at the step of the reduction of geranylgeranyl(gg)-Chl to dihydrogeranylgeranyl (dhgg)-Chl in Epicotyls, whereas phytyl-Chl was synthesized in leaves subjected to the same light treatments. Quantitative pigment analysis during continuous irradiations of different intensities also showed that significant Pchlide photodestruction occurred in Epicotyls even under weak light. When both Pchlide and chlorophyllide and/or chlorophylls were present in Epicotyls, Pchlide photodestruction was faster under 630-nm light than under 670-nm light, which indicates that this process is most efficiently promoted by Pchlide excitation. Pre-incubation of epicotyl segments with 10 mM ascorbate partly alleviated pigment photodestruction in white light. It is concluded that formation of photoactive Pchlide-Pchlide oxidoreductase complexes is important to prevent fast pigment photooxidation after Pchlide accumulation in the dark.