Changes in the Autolytic Activities of Maize Coleoptile Cell Walls during Coleoptile Growth

Autolytic activities of coleoptile cell walls were measuredin developing maize seedlings. The major neutral sugar componentsof the cell wall polysaccharides were arabinose, xylose andglucose. The quantities of all these components per coleoptileincreased for 5 d after germination, suggesting that levelsare augmented by biosynthetic processes during coleoptile growth.However, cell wall preparations isolated from the coleoptilesalso revealed increasing rates of autolytic activity directedtoward each of the sugar components. This result suggests thatthe constitutive hydrolytic activities expressed by cell wallsalso increase as a function of coleoptile age. The proportionof glucose in autolysis products relative to that present inthe cell walls specifically increased with coleoptile age, whilethe ratios for arabinose and xylose decreased. Kinetic analysesof autolysis demonstrated that the reactions specific for pentosesat the early growth stage are transient events and that initiallow rates of glucan autolysis increased sharply and persistedlonger. In these experiments the products of glucan autolysiswere largely monomeric while those of the pentose-specific reactionsconsisted of both monomeric and polymeric sugars. Based on theseresults, we concluded that two distinct phases of autolyticactivities are expressed in the mediation of cell wall polysaccharidemetabolism in situ. (Received July 17, 1996; Accepted November 25, 1996)     

Determination of Auxin-Dependent pH Changes in Coleoptile Cell Walls by a Null-Point Method

The present debate on the validity of the "acid-growth theory" of auxin (indole-3-acetic acid, IAA) action concentrates on the question of whether IAA-induced proton excretion into the cell wall is quantitatively sufficient to provide the shift in pH that is required to explain IAA-induced growth (see D.L. Rayle, R.E. Cleland [1992] Plant Physiol 99:1271-1274 for a recent apologetic review of the acid-growth theory). In the present paper a null-point method has been employed for determining the growth-effective cell-wall pH in the presence and absence of IAA after 60 min of treatment. Elongation of abraded maize (Zea mays L.) and oat (Avena sativa L.) coleoptile segments was measured with the high resolution of a displacement transducer. The abrasion method employed for rendering the outer epidermal cell wall permeable for buffer ions was checked with a dye-uptake method. Evidence is provided demonstrating that externally applied solutes rapidly and homogeneously penetrate into the epidermal wall, whereas penetration into the inner tissue walls is strongly retarded. "Titration" curves of IAA-induced and basal elongation were determined by measuring the promoting/inhibiting effect of medium pH under iso-osmotic conditions in the range of pH 4.5 to 6.0. In maize, the null point (no pH-dependent change in elongation rate after 5-10 min of treatment with 10 mmol L-1 citrate buffer) was pH 5.00 after 60 min of IAA-induced growth, and the null-point pH determined similarly in IAA-depleted tissue (10 times smaller elongation rate) was 5.25. Corresponding titration curves with Avena segments led to slightly lower null-point pH values both in the presence and absence of IAA-induced growth. After induction of acid-mediated extension by 1 [mu]mol L-1 fusicoccin (FC) in maize, the null-point pH shifted to 3.9. At 0.5 [mu]mol L-1, FC induced the same elongation rate as IAA but a 9-fold larger rate of proton excretion. At 0.033 [mu]mol L-1, FC induced the same rate of proton excretion as IAA but had no appreciable effect on elongation. The implications of these results against the background of recent attempts to revitalize the acid-growth theory of IAA action are discussed.     

Changes in the Molecular Weight Distribution of the Hemicellulosic Polysaccharides from Rice Coleoptiles Growing Under Different Conditions

The changes in the molecular weight distribution of water-solubleand water-insoluble hemicelluloses from the cell walls of ricecoleoptiles growing in air and under water were studied. Thegrowth of rice coleoptiles was remarkably enhanced by growingunder water. Water-insoluble hemicellulose, mainly constitutedby xyloglucan, suffered an important depolymerization duringcoleoptile growth. On the other hand, ß-glucan andarabinoxylan, the two main polysaccharides of the water-solublehemicelluloses showed different changes during coleoptile growth.ß-glucan showed an increase in its degree of polymerizationduring the coleoptile fast growth phase and it decreased beforecoleoptile growth ceased. Arabinoxylan did not show importantdifferences in its mass-average molecular weight. Thus, xyloglucanand ß-glucan are the two hemicellulosic polysaccharidesinvolved in the cell wall loosening mechanism during coleoptilegrowth under both culture conditions. Key words: Arabinoxylan, cell wall, ß-glucan, xyloglucan     

Changes in Neutral Sugar Compositions of Cell Wall Polysaccharides during Redifferentiation of Cultured Carrot Cells and during Maturation of Soybean Seeds

Changes in the neutral sugar compositions of cell walls werestudied during regeneration of shoots and roots from culturedcarrot cells and during maturation of soybean seeds. There weremore arabinan and arabinose-rich acidic polysaccharides thangalactose-rich polysaccharides in the pectic fractions of thecell walls from cultured carrot cells and more galactan, arabinogalactanor both than the arabinose-rich polysaccharides in the samefractions from their mother tissue, i.e. root phloem tissue. The arabinose content of the cell walls decreased and the galactosecontent increased during root and shoot formation until galactoseexceeded arabinose in the cell walls of fully developed shootsand roots from cultured cells. The cell wall arabinose contentalso was higher than that of galactose in cotyledons and embryonicaxes of immature soybean seeds, and change in the neutral sugarcomposition of the cell wall during seed maturation was similarto that during the redifTerentiation of cultured carrot cells.During the very late stage of maturation, galactose in the cellwalls exceeded the content of arabinose. Results suggest that the redifferentiation of roots and shootsfrom cultured cells goes through a process of cell wall formationsimilar to that of embryogenesis or seed development in themother plants. Results also indicate that the predominant arabinanand arabinose-rich acidic polysaccharides have important functionsin cell walls during embryogenesis and in the eraly stages ofseed maturation and that galactan, arabinogalactan, or bothreplace these arabinose-rich polysaccharides after seed maturation. ²Present address: Department of Botany, the University of BritishColumbia, # 3529-6270 University Blvd.,Vancouver, B.C. V6T 2B1Canada (Received October 28, 1982; Accepted April 8, 1983)     

Autolysis Promotes the Extension Capacity of Zea mays Coleoptile Cell Walls in Response to Acid pH Solutions

The relationship between autolytic degradation of ß(1–3),(1–4)-D-glucanand acid pH-induced extension of isolated Zea mays cell wallshas been investigated using a constant-load extension technique.Acidic buffer (4.5) was able to induce an additional extension(E_a) on cell walls already extended at pH 6.8 buffer under a20 g-mass load, indicating that the additional extension (E_a)was the parameter that better represented the effect of thedifferent treatments on the mechanical properties of maize coleoptilecell walls. The additional extension in response to acidic pHwas higher when cell walls had been previously autolysed for24 h at pH 5.5. Furthermore, the acid-pH effect was dependenton the presence during the constant load extension of some thermo-labilefactors, suggesting the participation of expansins. Acid pHincreased E_a of native cell walls through an increase in theplastic extension (E_p) in agreement with a one step mechanismleading directly to irreversible (plastic) wall extension assuggested by Cosgrove (1977). The autolytic degradation of ß(1–3),(1–4)-D-glucan was also able to modify the mechanicalproperties of maize coleoptile cell walls increasing its elasticextension (E_e) in response to pH 4.5 buffer but that modificationonly leads to an increase in wall extension when expansins areactive, suggesting a cooperation between ß-glucanturnover and expansin action. (Received August 5, 1998; Accepted March 16, 1999)     

植物细胞壁多糖合成酶系及真菌降解酶系

秸秆类植物细胞壁多糖高效降解转化对我国农业经济的绿色可持续发展具有重要意义,然而植物细胞壁在长期进化过程中形成了复杂结构限制了工业化酶解转化的过程。一方面从植物细胞壁多糖合成酶系的多样性、细胞壁多糖成分的复杂性、超分子结构的异质性等方面综述了形成植物细胞壁抗降解屏障的原因;另一方面从真菌降解植物细胞壁酶系的多样性、不同菌株降解酶组成差异性等分析降解转化植物细胞壁时发挥的不同作用,从而为工业转化合理复配真菌降解酶系,提高秸秆生物质的利用效率提供理论支持。     

Increased Molecular Mass of Hemicellulosic Polysaccharides is Involved in Growth Inhibition of Maize Coleoptiles and Mesocotyls under Hypergravity Conditions

Zea 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. Received 22 February 1999/ Accepted in revised form 20 April 1999     

Hemicellulosic Polysaccharides from the Xylopodium of Ocimum nudicaule: Changes in Composition in Dormancy and Sprouting

Changes in the yield and composition of hemicelluloses fromthe underground organs (xylopodia) of Ocimum nudicaule wereinvestigated. Hemicelluloses constituted about 12% of the delipidizedpowder in sprouting and about 30 % in dormant phases. Xyloseis the major component of hemicelluloses A and B (and is alsopresent in C), followed by arabinose, galactose, glucose, rhamnoseand mannose. The amounts of hemicellulose B decreased by sixtimes between dormancy and sprouting, whereas the yields ofhemicelluloses A and C remained constant. This, together withthe higher solubility of hemicellulose B and its higher susceptibilityto hemicellulase in sprouting indicates that this fraction constitutesa cell-wall bound storage polysaccharide, which may play a rolein the onset of xylopodia bud sprouting. Ocimum nudicaule, hemicelluloses, cell-wall storage polysaccharide     

Intrinsic Nitric Oxide Regulates the Taste Response of the Sugar Receptor Cell in the Blowfly, Phormia regina

Chemical Senses, 29, 75–81, 2004 Regrettably,     

Jasmonic Acid Inhibits the IAA-Induced Elongation of Oat Coleoptile Segments: a Possible Mechanism Involving the Metabolism of Cell Wall Polysaccharides

The effects of jasmonic acid (JA) on the IAA-induced elongationof segments of etiolated oat (Avena sativa L. cv. Victory) coleoptileswere studied. Exogenously applied JA substantially inhibitedIAA-induced elongation of oat coleoptile segments. The inhibitionof the growth of oat coleoptile segments due to JA appeared2 h after the application of JA with IAA. JA did not affectthe consumption of oxygen by the segments, the osmolarity ofthe cell sap or the IAA-induced loosening of cell walls, whichwas recognized as a decrease in the minimum stress-relaxationtime (T₀). JA was extremely effective in preventing increasesin the amount of the cell wall polysaccharides in both the non-cellulosicfraction and the cellulosic fraction during coleoptile growthin the presence and in the absence of IAA. Inhibition of thegrowth of oat coleoptile segments induced by JA was partiallyreversed by the simultaneous addition of sucrose to the testsolution. From these results, it appears that JA inhibits IAA-inducedelongation of oat coleoptile segments by interfering with someaspects of sugar metabolism that are related to the degradationand/or the synthesis of cell wall polysaccharides. (Received March 15, 1994; Accepted August 2, 1994)     

Fractionation and Partial Characterization of Pectic Polysaccharides in Cell Walls from Liverwort (Marchantia polymorph) Cell Cultures

Konno, H., Yamasalu, Y. and Katoh, K. 1987. Fractionation andpartial characterization of pectic polysaccharides in cell wallsfrom liverwort (Marchantia polymorpha) cell cultures.—Jexp. Bot. 38: 711–722. Pectic polysaccharides were extracted from the starch-free cellwall preparation of cell suspension cultures of Marchantia polymorpha.The polysaccharides were fractionated by DEAE-Sephadex A-50ion-exchange chromatography yielding the five fractions, andthe degree of polymerization and glycosyl composition determinedfor each fraction. The neutral rich and acidic pectic polymerswere depolymerized by purified endoglucanase (l,4-ß-D-glucan4-glucanohydrolase, E.C. 3.2.1.4 [EC] .) and endopolygalacturonase(poly-l,4--Dgalacturonide glycanohydrolase, E.C. 3.2.1.15 [EC] ),respectively. The degraded pectic fractions were fractionatedby gel filtration chromatography on Bio-Gel A-5m and Bio-GelP-2, and glycosyl composition determined for each fraction.The results indicate that pectic polysaccharides contain glucose-richpolymer, rhamnogalacturonan and homogalacturonan in a ratioof 1:4:0–6. In addition, pectic polysaccharides were releasedas five pectic fragments from the cell walls by purified endopectatelyase (poly-l,4--D-galacturonide lyase, E.C. 4.2.2.2 [EC] ). Basedon the analysis of glycosyl composition of each fragment, thepectic polysaccharides of Marchantia cell walls are characterized Key words: Cell suspension culture, cell wall, liverwort, Marchantia polymorpha, pectic polysaccharides     

Disintegration of Microorganisms and Preparation of Yeast Cell Walls in a New Type of Disintegrator

Microbial cells were disintegrated in a new type of rotary disintegrator with a disc stirrer by a combination of shear force layers, collisions, and rolling of glass beads which were brought into motion by the stirrer. The rate of disintegration at a given dry bed volume of Ballotini beads and a given volume of cell suspension is proportional to the peripheral velocity of the stirrer up to 18 m/sec. Horizontal arrangement of the stirrer increases the effectiveness about five times; 100% disintegration of yeast cells was achieved under optimal conditions within 72 sec at a concentration of 3.5g (dry weight)/100 ml of suspension, and within 96 sec at a concentration of 10.5g (dry weight)/100ml. At 17.5 g (dry weight)/100 ml, the stirrer began to slip. The cell walls of yeast were obtained at the desired degree of crushing and the course of purification was determined by infrared spectral analysis.     

Effect of Rust Infection on Cell Walls of Barley and Wheat; Immunocytochemistry Using Anti-Barley Thionin as a Probe

Polyclonal antiserum prepared against barley cell wall thionin was used to localize and quantitate immunoreactive material on the cellular level in healthy and rust-infected leaves of barley and wheat. Three types of sites were used for the immunocytochemical analysis: as control sites, mesophyll cell walls were selected in uninoculated leaves, and in leaves that were inoculated with rust but where the sites were not in contact with the pathogen: these were compared with mesophyll cell walls that were in contact with intercellular rust hyphae in inoculated leaves.
Similar amounts of cell wall thionin were detected in all 3 barley cultivars before inoculation. At sites where intercellular hyphae of Puccinia hordei had made contact with mesophyll cell walls, less thionin was found in the compatible host cv. Larker, but in incompatible hosts (cvs. Gold and Bolivia) the thionin concentration did not differ from that of the controls.
Two cultivars of wheat were studied with respect to immunoreactive material in their mesophyll cell walls, the universal rust suscept cv. Little Club and the highly rust-resistant cv. Khapli. Before inoculation, leaves of cv. Khapli contained about twice the amount of immunoreactive material in mesophyll cell walls than those of cv. Little Club. This relation was unchanged in walls that had made contact with P. graminis tritici , but in non-contacted walls of infected cv. Little Club leavest, he concentration of this material had risen to levels typical for those of cv. Khapli. Tests for immunoreactive material with pre-embedding cytochemistry yielded negative results, indicating that it is not exposed on the surface of mesophyll walls in barley and wheat.     

Transient Nature of a (1 --> 3), (1 --> 4)-beta-d-Glucan in Zea mays Coleoptile Cell Walls

Excised Zea mays L. embryos were cultured on Linsmaier and Skoog medium. Coleoptiles were sampled at regular intervals and the length, fresh weight, cell wall weight, and cell wall neutral sugar composition were determined. A specific β-d-glucanase from Bacillus subtilis was used to determine the content of a (1 → 3),(1 → 4)-β-d-glucan.     

The Structure of Plant Cell Walls: I. The Macromolecular Components of the Walls of Suspension-cultured Sycamore Cells with a Detailed Analysis of the Pectic Polysaccharides

This is the first in a series of papers dealing with the structure of cell walls isolated from suspension-cultured sycamore cells (Acer pseudoplatanus). These studies have been made possible by the availability of purified hydrolytic enzymes and by recent improvements in the techniques of methylation analysis. These techniques have permitted us to identify and quantitate the macromolecular components of sycamore cell walls. These walls are composed of 10% arabinan, 2% 3,6-linked arabinogalactan, 23% cellulose, 9% oligo-arabinosides (attached to hydroxyproline), 8% 4-linked galactan, 10% hydroxyproline-rich protein, 16% rhamnogalacturonan, and 21% xyloglucan.     

Growth and Stress-Relaxation Parameters for the Cell Wall of Normal and 10 Dwarf Barley Strains

Mechanical properties of the cell wall of 2- and 3-day-old barleycoleoptiles of normal and 10 dwarf strains were measured toexplain their different growth rates. Six parameters for mechanicalproperties (minimum and maximum stress relaxation time, relaxationrate, residual stress, strain ratio and the apparent Young'smodulus) were obtained by use of a stress-relaxation technique. The minimum stress-relaxation time and relaxation rate on day2, when the coleoptiles of all the strains had their maximumgrowth rates, were correlated significantly with the growthrates (r=0.79 and 0.72). When coleoptile growth in all the strainswas slowing down, the apparent Young's modulus was correlatedto the final coleoptile length. These results suggest (1) that when the coleoptile cell is activelygrowing, the minimum stress-relaxation time and relaxation rateof the cell wall affect the growth rate and (2) that the apparentYoung's modulus limits the final coleoptile length of the barleystrains examined. (Received October 13, 1983; Accepted April 16, 1984)