Enzymic analysis of cell wall structure in apple fruit cortical tissue

Galactanase from Phytophthora infestans and an arabinosidase isoenzyme from Sclerotinia fructigena attacked the cortical cell walls of apple fruits liberating galactose and arabinose residues, respectively. Other arabinosidase isoenzymes from S. fructigena attacked cell walls very slowly. A S. fructigena polygalacturonase isoenzyme liberated half of the uronic acid residues with few associated neutral residues, while a second polygalacturonase isoenzyme released more uronic acid with a substantial proportion of arabinose and galactose and lesser amounts of xylose, rhamnose and glucose; reaction products of this enzyme could be further degraded by the first isoenzyme to give high MW fragments, rich in arabinose with most of the xylose, rhamnose and glucose, and low MW fragments rich in galactose and uronic acid. Endoglucanase from Trichoderma viride released a small proportion of the glucose residues from cell walls together with uronic acid, arabinose, xylose and galactose; more extensive degradation occurred if walls were pre-treated with the second polygalacturonase isoenzyme. Endoglucanase reaction products were separated into a high MW fraction, rich in arabinose, and lower MW fractions rich in galactose and glucose residues. The high MW polygalacturonase and endoglucanase products could be degraded with an arabinosidase isoenzyme to release about 75% of their arabinose. Cell walls from ripe fruit showed similar susceptibility to arabinosidase and galactanase to those from unripe apples. Cell walls from fruit, ripened detached from the tree were more susceptible to degradation by polygalacturonase than walls from unripe fruit or fruit ripened on the tree. Endoglucanase released less carbohydrate from ripe fruit cell walls than from unripe fruit cell walls.     

中性糖在土壤中的来源与分布特征

糖类(即碳水化合物)是土壤有机质的重要组成部分, 经生物化学降解形成不同结构的单糖。土壤中的中性单糖也叫中性糖, 主要包括木糖、核糖、阿拉伯糖、葡萄糖、半乳糖、甘露糖、岩藻糖和鼠李糖。其中, 植物来源的糖主要为五碳糖, 如木糖和阿拉伯糖; 微生物来源的糖主要包括半乳糖、甘露糖、岩藻糖、鼠李糖等六碳糖。研究中常利用六碳糖和五碳糖的比例指示微生物和植物对土壤有机碳的相对贡献。中性糖是微生物重要的碳源和能量来源, 在团聚体的形成过程中扮演着重要角色。该文整合了近30年土壤中性糖的研究进展, 对比了提取中性糖的常用方法, 分析了不同土地利用类型和不同土壤组分中中性糖的含量、来源和周转特征, 综述了影响中性糖含量和分布的主要环境因素。结果表明, 中性糖在耕地土壤中的绝对含量和相对含量均显著低于针叶林、阔叶林、草地和灌丛4种土地利用类型。(半乳糖+甘露糖)/(阿拉伯糖+木糖)(GM/AX)在不同土地利用间差异不显著, 而(鼠李糖+岩藻糖)/(阿拉伯糖+木糖)(RF/AX)则表明草地土壤中的微生物来源的中性糖含量高于针叶林和耕地。不同密度的土壤组分中, 轻质组分中中性糖的含量比重质组分高, 重质组分中微生物来源的中性糖较多; 就不同粒径(或团聚体)而言, 黏粒(或微团聚体)中微生物来源的中性糖含量更丰富。有关影响土壤中性糖含量和分布的因素的研究, 目前主要集中在人为活动(如耕种和放牧等), 而有关温度、降水等自然环境因素影响的研究较少。     

Structural aspects of the exudate from the fruit of Chorisia speciosa St. Hil

Mature fruit of Chorisia speciosa yield an exudate (E-I) following mechanical injury. The polysaccharide contains rhamnose, arabinose, xylose, mannose, glucose, galactose and glucuronic acid in molar ratios of 20:11:1:3:2:40:23. The main chain of the structure is composed by beta-galactopyranosyl units linked (1 --> 3) and (1 --> 6) as indicated by NMR spectra and methylation data. Arabinosef and rhamnose are terminal residues. In order to compare E-I with the polysaccharides from the fruit mesocarp, the latter was submitted to different extractions. The water fraction contains rhamnose, arabinose, xylose, mannose, glucose, galactose and uronic acid in molar ratios of 18:4:1:2:3:44:28. It was treated with CTAB yielding a precipitate which was decomplexed with NaCl, giving four fractions. The fraction obtained using 0.15 M NaCl had a quantitative composition similar that of E-I.     

Composition and properties of Opuntia ficus-indica mucilage

The mucilage isolated from Opuntia is shown to contain arabinose, galactose, galacturonic acid, rhamnose and xylose. It has a uronic acid content of ca 10% and a MW of 4.3 × 10⁶. It equilibrates to 175% of its dry wt at 100% relative humidity. Its possible role in the physiology of the plant is discussed.     

Dynamics of amino acids in the conditioning film developed on glass panels immersed in the surface seawaters of Dona Paula Bay

The conditioning film developed on glass panels immersed in surface seawater over a period of 24?h was analysed for total organic carbon (OC), total organic nitrogen (ON), and total hydrolyzable amino acid (THAA) concentrations and composition. The concentrations of C and N and THAA increased, whereas the C/N ratio decreased over the period of immersion. The amino acid-C and N accounted for 3.7?–?6.7% and 10.3?–?65.3% of OC and ON, respectively. The relative contribution of glycine plus threonine and serine to the total amino acids decreased while that of valine, phenylalanine, isoleucine and leucine increased over the period of immersion. Principal component analysis (PCA) based on mole% amino acid composition showed that the degradation indices (DI) for the conditioning film organic matter increased over the period of immersion. A high C/N ratio, a low %THAA-C, % THAA-N and DI values and the abundance of glycine plus threonine and serine in the conditioning film organic matter during the first few hours following immersion imply that the adsorbed organic matter was mostly derived from degraded organic matter.     

The extracellular proteoglycan produced by Rhodella grisea

Highly viscous extracellular proteoglycan (EPG) has been isolated from culture medium of the unicellular red alga Rhodella grisea (Rhodophyceae) by ethanol precipitation. EPG was composed of xylose (29.3%), 3-O-methyl-xylose (26.0%), uronic acids (17.1%), rhamnose (14.4%), galactose (7.5%), glucose (3.9%), arabinose (1.4%) and mannose (0.4%), and traces of fucose, 4-O-methyl-xylose and 2,3-di-O-methyl-rhamnose or fucose. In addition, the polymer contained proteins (13.1%), sulphates and 13C-CP MAS spectra indicated the presence of acetyl and succinyl groups. The molecular mass was estimated to be 136,000. Ion-exchange chromatography afforded five fractions differing in composition of neutral sugars, uronic acids, and protein content indicating thus the complex structure of the EPG.     

Resolution of the enantiomers of aldoses by liquid chromatography of diastereoisomeric 1-(N-acetyl-α-methylbenzylamino)-1-deoxyalditol acetates

Acyclic diastereoisomers, namely, 1-(N-acetyl-α-methylbenzylamino)-1-deoxyalditol acetates are readily obtained by reductive amination of aldoses with chiral α-methylbenzylamine (MBA) in the presence of sodium cyanoborohydride, and may be separated by reversed-phase 1.c. and, more effectively, by adsorption 1.c. According to this procedure, enantiomers of the common, neutral aldoses are resolved. In adsorption 1.c., l-l_* [defined as an adduct of an l-aldose and l-(-)-MBA] is eluted before d-l_* for erythrose, xylose, ribose, glucose, 4-O-methylglucose, galactose, and fucose, and the elution order is the reverse for arabinose, lyxose, mannose, rhamnose, and glyceraldehyde. This behavior is probably related to the configuration of C-2 of the aldoses.     

Analytical and structural features of the gum exudate from Combretum hartmannianum schweinf.

The gum exudate from Combretum hartmannianum is water-soluble, forms very viscous solutions, and contains galactose (22%), arabinose (43%), mannose (10%), xylose (6%), rhamnose (4%), glucuronic acid (6%), 4-O-methylglucuronic acid (2%), and galacturonic acid (7%). The acidic components produced on hydrolysis of the gum were 6-O-(β-D-glucopyranosyluronic acid)-D-galactose, and two saccharides that had the same chromatographic mobility, and contained mannose and galacturonic acid, and galactose and 4-O-methylglucuronic acid, respectively. Methylation and methanolysis of the gum indicated the presence of terminal uronic acid, rhamnose, xylose, galactose, arabinofuranose, and arabinopyranose. Controlled, acid hydrolysis indicated the presence of (1→3)-linked arabinopyranose side-chains and (1→6)-linked galactose residues. C. hartmannianum gum, when subjected to two Smith-degradations, yielded Polysaccharides I and II, both of which contained galactose, arabinose, and mannose. Insufficient crude gum was available for a complete structural study, but the molecule was shown to contain long, sparsely branched chains of (1→6)-linked galactose residues, to which are attached (1→3)-linked arabinose and (1→3)-linked mannose side-chains.     

Mathematical modeling of soil carbon turnover in natural Podocarpus forest and Eucalyptus plantation in Ethiopia using compound specific δ13C analysis

Forest soils exhibit huge potential in storing carbon, but may also release large amounts of it if they undergo major changes in land use and environmental conditions. Biogeochemical processes controlling accumulation and release of soil organic carbon (SOC) are not yet sufficiently understood. We investigate the dynamics of SOC depending on its chemical composition below a natural forest (Podocarpus falcatus dominated) and a plantation (Eucalyptus saligna) growing on Nitisols in southern Ethiopia. Soils at the study‐site show a huge shift to less negative δ¹³C values at a depth of 20–30 cm, indicating a change from C4 savanna to C3 forest during the late Holocene. Total organic carbon (TOC), black carbon (BC), and sugars from microbial (rhamnose, fucose) and plant origin (xylose, arabinose) are subjected to compound‐specific stable isotope analysis. Turnover characteristics are calculated using a numerical advection–diffusion–decomposition model. Our measurements show significant differences in carbon storage (P<0.05) for both sites (Podocarpus 23.5 ± 3.2 kg SOC m^?3; Eucalyptus 18.6 ± 2.7 kg SOC m^?3). These differences can be explained with an initial loss of 15–26% of TOC about 50 years ago, induced by clearing the natural forest. After canopy closure, the carbon input below Eucalyptus is 15–34% less than below natural forest. At present, mean residence times (MRTs) of the investigated compounds do not differ between both stands. Sugars show the shortest MRTs in the topsoil with 2–7 years (xylose) and 5–13 years (arabinose) and have been affected the most by clear‐cutting. TOC and BC show MRTs of 13–25 years and 20–34 years, respectively. Old C4 carbon below 20 cm has merely been affected by the land use change. Contrary to expectation, our study does not indicate a pronounced recalcitrance of BC.     

裙带菜褐藻糖胶的分离纯化及其结构分析

裙带菜经水提法提取得到褐藻糖胶粗多糖,经DEAE-Sepharose FF离子交换层析和 Sepharose 4B层析后,得到Sl、S2两个单一组分,相对分子质量分别为550 808、38 335.基本结构及单糖组成分析表明,二者均含有岩藻糖、糖醛酸、硫酸基、半乳糖、甘露糖、葡萄糖、鼠李糖、木糖、阿拉伯糖,但含量差别较大,推测与二者的生理活性的差异有关.     

Isolation of a polysaccharide from the inner cell wall, intine, of pollen of Cryptomeria japonica

Isolation and solubilization of the intine of pollen grainsof Cryptomeria japonica were attempted. The intine was separatedeffectively from other cell fragments by passing it througha column of glass beads and dissolving it in an EDTA solution.The extract was fractionated by column chromatography on DEAE-celluloseand gelfiltration through Sephadex G-200, and a polysaccharidecomponent was obtained. This was found to consist of galactose,rhamnose, arabinose, xylose and uronic acid. (Received October 13, 1976; )     

A note on the formation of microbial polysaccharide from wheat straw decomposed in the absence of soil

C hapman , S.J. & L ynch , J.M. 1984. A note on the formation of microbial polysaccharide from wheat straw decomposed in the absence of soil. Journal of Applied Bacteriology 56 , 337–342.
The proportions of neutral sugars in fresh and decomposed wheat straw polysaccharide were similar, irrespective of the oxygen concentration used during breakdown. Polysaccharide extracted by hot water from the decomposed straw was composed mainly of galactose, glucose and mannose with smaller quantities of arabinose, xylose, rhamnose, fucose and ribose. The presence of these sugars indicates a mainly microbial origin for the polysaccharide but with some soluble hemi-cellulose breakdown products. The polysaccharide precipitable with 70% (v/v) ethanol accounted for 0.5% (w/w) of the degraded straw. The extracted polysaccharide was shown to increase the aggregate stability of Mount St Helens volcanic ash.     

Production and composition of extracellular polysaccharide from cell suspension cultures of Mentha

A suspension culture of Mentha was established from callus which formed on the tips of young shoots of a Mentha hybrid (M. arvenis × M. spicata). Changes in growth parameters during a culture cycle were recorded. The general appearance of cells during division and growth, including the changes in cell form, was also represented.Suspension-cultured cells of Mentha hybrid released a large amount of extracellular polysaccharides (ECP) mainly at the logarithmic phase of the growth cycle. The ECP contained galacturonic acid as major components and arabinose, galactose, glucose, xylose, rhamnose and mannose as minor components. The ratio of the uronic acid content to total sugar content in the ECP was below 40% at day 7, but increased up to 90% at day 21. The relative contents of xylose and glucose in the ECP decreased during the culture period, while the arabinose content increased and those of rhamnose, mannose and galactose remained constant.The IR spectrum suggested that the ECP were low-methoxylated pectic polysaccharides. The presence of lignin and related compounds in the ECP was not detected. The protein content of the ECP was about 10% and the main amino acids were alanine, proline, hydroxyproline, valine, asparticacid and serine, in that order.     

Rumen digestion of rice straw structural polysaccharides: effect of ammonia treatment and lucerne extract supplementation in vitro

The combined effects of lucerne (Medicago sativa L.) extract supplementation and ammonia treatment of rice straw (Oryza sativa, variety Thaibonnet) on the ruminal digestion of cell wall components were investigated in six continuous culture systems using a randomised complete block design. Data were fitted to second-order polynomial models. Untreated rice straw had higher contents of ash-free cell wall residues (CWR; 763 v. 687 g/kg dry matter (DM)) and non-cellulosic sugars (191 v. 166 g/kg DM) than treated rice straw. Ammoniation preferentially removed xylose, which resulted in a lower xylose-to-arabinose ratio (5.1 v. 5.8). In absence of lucerne supplementation and ammoniation, degradability coefficients were 0.54, 0.46, 0.58, 0.54, 0.42 and 0.60 for cellulose–glucose, xylose, arabinose, galactose, mannose and uronic acids, respectively. Both factors had significant effects on the microbial degradation of structural polysaccharides. With lucerne extract at an optimal level, ammonia treatment increased ash-free cell wall degradation by more than 10%. The degradability coefficients were increased by ammoniation without any significant interaction with lucerne extract, except for glucose, whose degradability was mostly influenced by lucerne extract in a curvilinear way. The comparison of regression coefficients in cell wall and CWR models suggested that ammoniation improved the degradabilities of xylose, galactose and mannose by partly solubilising the corresponding hemicelluloses and by improving the susceptibility of the remaining fraction to microbial attack, whereas it increased the degradability of arabinose only by favouring microbial attack.     

Tomato fruit cell wall : I. Use of purified tomato polygalacturonase and pectinmethylesterase to identify developmental changes in pectins

Cell wall isolation procedures were evaluated to determine their effect on the total pectin content and the degree of methylesterification of tomato (Lycopersicon esculentum L.) fruit cell walls. Water homogenates liberate substantial amounts of buffer soluble uronic acid, 5.2 milligrams uronic acid/100 milligrams wall. Solubilization appears to be a consequence of autohydrolysis mediated by polygalacturonase II, isoenzymes A and B, since the uronic acid release from the wall residue can be suppressed by homogenization in the presence of 50% ethanol followed by heating. The extent of methylesterification in heat-inactivated cell walls, 94 mole%, was significantly greater than with water homogenates, 56 mole%. The results suggest that autohydrolysis, mediated by cell wall-associated enzymes, accounts for the solubilization of tomato fruit pectin in vitro. Endogenous enzymes also account for a decrease in the methylesterification during the cell wall preparation. The heat-inactivated cell wall preparation was superior to the other methods studied since it reduces β-elimination during heating and inactivates constitutive enzymes that may modify pectin structure. This heat-inactivated cell wall preparation was used in subsequent enzymatic analysis of the pectin structure. Purified tomato fruit polygalacturonase and partially purified pectinmethylesterase were used to assess changes in constitutive substrates during tomato fruit ripening. Polygalacturonase treatment of heat-inactivated cell walls from mature green and breaker stages released 14% of the uronic acid. The extent of the release of polyuronides by polygalacturonase was fruit development stage dependent. At the turning stage, 21% of the pectin fraction was released, a value which increased to a maximum of 28% of the uronides at the red ripe stage. Pretreatment of the walls with purified tomato pectinesterase rendered walls from all ripening stages equally susceptible to polygalacturonase. Quantitatively, the release of uronides by polygalacturonase from all pectinesterase treated cell walls was equivalent to polygalacturonase treatment of walls at the ripe stage. Uronide polymers released by polygalacturonase contain galacturonic acid, rhamnose, galactose, arabinose, xylose, and glucose. As a function of development, an increase in the release of galacturonic acid and rhamnose was observed (40 and 6% of these polymers at the mature green stage to 54 and 15% at the red ripe stage, respectively). The amount of galactose and arabinose released by exogenous polygalacturonase decreased during development (41 and 11% from walls of mature green fruit to 11 and 6% at the red ripe stage, respectively). Minor amounts of glucose and xylose released from the wall by exogenous polygalacturonase (4-7%) remained constant throughout fruit development.     

Characterization of Pseudomonas paucimobilis FP2001 Which Forms Flagella Depending upon the Presence of Rhamnose in Liquid Medium

A bacterial strain FP2001 isolated from the exudate of land reclaimed for municipal waste was identified as Pseudomonas paucimobilis. Cells of strain FP2001 were mobile by means of polar monotrichous flagellum, only when rhamnose was added as a carbon source in the liquid medium. The replacement of rhamnose by arabinose, galactose, glucose or xylose did not lead to the formation of flagella.     

Partial structure of a polysaccharide from leaves of Welwitschia mirabilis

Gum-tears from the leaves of Welwitschia mirabilis contain a polysaccharide composed of arabinose, galactose and glucuronic acid as main constituents with xylose, fucose and rhamnose in smaller quantities. Periodate oxidation and permethylation studies indicated that the gum could consist of a framework of glucuronic acid residues linked 1 → 4 and galactose residues linked 1 → 6 and of short chains of arabinose, xylose, fucose and rhamnose linked 1 → 3 to both residues. All rhamnose and fucose and part of arabinose were found as non-reducing terminal units.     

Comparison between maize root cells and their respective regenerating protoplasts: wall polysaccharides

The cell-wall polysaccharides from different parts of maize roots have been analysed. The arabinose, galactose and mannose contents are influenced by cell differentiation, whereas xylose, rhamnose and uronic-acid contents are not. In cap cells, the pectin content is low but rhamnose and fucose are present in larger quantities. The cell-wall polysaccharides from cells of the elongation zone and their respective regenerating protoplasts were also analysed. The walls of the protoplasts contained higher xylose and mannose levels and a much lower level of cellulose than the cells from which they were derived.     

Activity of cell-wall degradation associated with differentiation of isolated mesophyll cells of Zinnia elegans into tracheary elements

Cell walls were prepared from cultured mesophyll cells of Zinnia elegans L. that were transdifferentiating into tracheary elements and incubated in a buffer to undergo autolysis. The rate of autolysis of cell walls was determined by measuring the amount of carbohydrate released from the cell walls into the buffer during incubation. During the course of culture of mesophyll cells, the autolysis rate increased markedly at the time when thickenings of secondary cell walls characteristic of tracheary elements became visible (after 48-72 h of culture), and thereafter the rate remained at a high level. Comparative studies on the autolysis rate of cell walls using various control cultures, in which tracheary element differentiation did not take place, revealed a close relationship between the autolysis rate around the 60th hour of culture and differentiation. Sugar analysis by colorimetric assays and gas chromatography of carbohydrates released from the cell walls detected uronic acid, arabinose, galactose, glucose, xylose, rhamnose, fucose, and mannose. Among these sugars, uronic acid was the most abundant, and accounted for approximately half of the total released sugars. The decrease of acidic polysaccharides in the primary cell walls during tracheary element differentiation was visualized by staining cultured cells with alcian blue at pH 2.5. These results suggest that active degradation of components of primary cell walls, including pectin, is integrated into the program of tracheary element differentiation.