Changes In Cell Wall Polysaccharides Research Articles

Relationship between submergence of graft union and auxin accumulation of grafted mango trees under flooded conditions

ABSTRACT In recent years, many fields have been affected by floods. In mango trees, grafted trees are more susceptible to flood damage than seedling trees, When the graft union is submerged. In this study, the translocation of substances, especially auxin, through the graft union was investigated to clarify the causes of death in mango trees when the trunk was submerged up to the graft union. After approximately 1 month of flooding, changes were observed in root respiration, carbon dioxide release from the trunk, and leaf stomatal conductance. The auxin content in the scion increased significantly from 19.5 ng g−1 dry weight (DW) in the control to 122.1 ng g−1 (DW) in the flooded treatment. Nevertheless, no significant increase in auxin content was observed in the rootstock. In addition, there was no pectin degradation, leading to the death of the grafted mango trees. Auxin accumulation induces expansins, which are cell wall proteins that loosen the cell wall structure and are involved in structural changes in cell wall polysaccharides. Therefore, submergence of the graft union may inhibit auxin translocation between the scion and rootstock, resulting in pectin degradation in the scion bark and leading to tissue breakdown and death of the mango tree.

Transcriptome analysis integrated with changes in cell wall polysaccharides of different fresh-cut chili pepper cultivars during storage reveals the softening mechanism

Cell wall disassembly and transcriptomic changes during storage of two fresh-cut chili pepper cultivars displaying contrasting softening rates were investigated. Results showed that Hangjiao No. 2 (HJ-2) softened more rapidly than Lafeng No. 3 (LF-3). Compared with LF-3, HJ-2 had a higher content of WSP, more side chains of RG-I in three pectin fractions, and higher activities of PME, PL, and β-Gal at day-0. During storage, HJ-2 showed more markable pectin solubilization, more severe degradation in CSP and NSP, and greater loss of side chains from RG-I in three pectin fractions, which were correlated with increased activities of PG and α-L-Af. Furthermore, the higher up-regulation of PG (LOC107870605, LOC107851416) and α-L-Af (LOC107848776, LOC107856612) were screened in HJ-2. In conclusion, the different softening rate between cultivars was not only due to the fundamental differences in pectin structure but also pectin degradation regulated by related enzymes and gene expression levels.

Impact of cell wall polysaccharide modifications on the performance of Pichia pastoris: novel mutants with enhanced fitness and functionality for bioproduction applications

BackgroundPichia pastoris is a widely utilized host for heterologous protein expression and biotransformation. Despite the numerous strategies developed to optimize the chassis host GS115, the potential impact of changes in cell wall polysaccharides on the fitness and performance of P. pastoris remains largely unexplored. This study aims to investigate how alterations in cell wall polysaccharides affect the fitness and function of P. pastoris, contributing to a better understanding of its overall capabilities.ResultsTwo novel mutants of GS115 chassis, H001 and H002, were established by inactivating the PAS_chr1-3_0225 and PAS_chr1-3_0661 genes involved in β-glucan biosynthesis. In comparison to GS115, both modified hosts exhibited a looser cell surface and larger cell size, accompanied by faster growth rates and higher carbon-to-biomass conversion ratios. When utilizing glucose, glycerol, and methanol as exclusive carbon sources, the carbon-to-biomass conversion rates of H001 surpassed GS115 by 10.00%, 9.23%, and 33.33%, respectively. Similarly, H002 exhibited even higher increases of 32.50%, 12.31%, and 53.33% in carbon-to-biomass conversion compared to GS115 under the same carbon sources. Both chassis displayed elevated expression levels of green fluorescent protein (GFP) and human epidermal growth factor (hegf). Compared to GS115/pGAPZ A-gfp, H002/pGAPZ A-gfp showed a 57.64% higher GFP expression, while H002/pPICZα A-hegf produced 66.76% more hegf. Additionally, both mutant hosts exhibited enhanced biosynthesis efficiencies of S-adenosyl-L-methionine and ergothioneine. H001/pGAPZ A-sam2 synthesized 21.28% more SAM at 1.14 g/L compared to GS115/pGAPZ A-sam2, and H001/pGAPZ A-egt1E obtained 45.41% more ERG at 75.85 mg/L. The improved performance of H001 and H002 was likely attributed to increased supplies of NADPH and ATP. Specifically, H001 and H002 exhibited 5.00-fold and 1.55-fold higher ATP levels under glycerol, and 6.64- and 1.47-times higher ATP levels under methanol, respectively, compared to GS115. Comparative lipidomic analysis also indicated that the mutations generated richer unsaturated lipids on cell wall, leading to resilience to oxidative damage.ConclusionsTwo novel P. pastoris chassis hosts with impaired β-1,3-D-glucan biosynthesis were developed, showcasing enhanced performances in terms of growth rate, protein expression, and catalytic capabilities. These hosts exhibit the potential to serve as attractive alternatives to P. pastoris GS115 for various bioproduction applications.

Immune activation during Pseudomonas infection causes local cell wall remodeling and alters AGP accumulation.

The plant cell boundary generally comprises constituents of the primary and secondary cell wall (CW) that are deposited sequentially during development. Although it is known that the CW acts as a barrier against phytopathogens and undergoes modifications to limit their invasion, the extent, sequence, and requirements of the pathogen-induced modifications of the CW components are still largely unknown, especially at the level of the polysaccharide fraction. To address this significant knowledgegap, we adopted the compatible Pseudomonas syringae-Arabidopsis thaliana system. We found that, despite systemic signaling actuation, Pseudomonas infection leads only to local CW modifications. Furthermore, by utilizing a combination of CW and immune signaling-deficient mutants infected with virulent or non-virulent bacteria, we demonstrated that the pathogen-induced changes in CW polysaccharides depend on the combination of pathogen virulence and the host's ability to mount an immune response. This results in a pathogen-driven accumulation of CWhexoses, such as galactose, and an immune signaling-dependent increase in CW pentoses, mainly arabinose, and xylose. Our analyses of CW changes during disease progression also revealed a distinct spatiotemporal pattern of arabinogalactan protein (AGP) deposition and significant modifications of rhamnogalacturonan sidechains. Furthermore, genetic analyses demonstrated a critical role of AGPs, specifically of the Arabinoxylan Pectin Arabinogalactan Protein1, in limiting pathogen growth. Collectively, our results provide evidence for the actuation of significant remodeling of CW polysaccharides in a compatible host-pathogen interaction, and, by identifying AGPs as critical elements of the CW in plant defense, they pinpoint opportunities to improve plants against diverse pathogens.

Chitinase-Like Protein PpCTL1 Contributes to Maintaining Fruit Firmness by Affecting Cellulose Biosynthesis during Peach Development.

The firmness of the flesh fruit is a very important feature in the eating process. Peach fruit is very hard during development, but its firmness slightly decreases in the later stages of development. While there has been extensive research on changes in cell wall polysaccharides during fruit ripening, little is known about the changes that occur during growth and development. In this study, we investigated the modifications in cell wall components throughout the development and ripening of peach fruit, as well as its impact on firmness. Our findings revealed a significant positive correlation between fruit firmness and cellulose content at development stage. However, the correlation was lost during the softening process, suggesting that cellulose might be responsible for the fruit firmness during development. Members of the chitinase-like protein (CTL) group are of interest because of their possible role in plant cell wall biosynthesis. Here, two CTL homologous genes, PpCTL1 and PpCTL2, were identified in peach. Spatial and temporal expression patterns of PpCTLs revealed that PpCTL1 exhibited high expression abundance in the fruit and followed a similar trend to cellulose during fruit growth. Furthermore, silencing PpCTL1 expression resulted in reduced cellulose content at 5 DAI (days after injection), this change that would have a negative effect on fruit firmness. Our results indicate that PpCTL1 plays an important role in cellulose biosynthesis and the maintenance of peach firmness during development.

Dynamic Changes in Cell Wall Polysaccharides during Fruit Development and Ripening of Two Contrasting Loquat Cultivars and Associated Molecular Mechanisms.

Loquats have drawn much attention due to their essential nutrients and unusual phenology, which fills a market gap in early spring. Fruit firmness (FF) is one of the most important quality attributes. Dynamic changes in FF, cell wall (CW) polysaccharides, CW hydrolase activity, and expression of CW metabolism-related genes during the fruit development and ripening stages of two contrasting loquat cultivars were compared. Although the two cultivars possessed similar FF at the initial fruitlet stage, Dawuxing was significantly firmer than Ninghaibai at all subsequent time points. FF was positively correlated with the contents of covalent-soluble pectin and hemicellulose, activity of peroxidase, and gene expressions of PME, EG, CAD6, and POD; and negatively correlated with the contents of water-soluble pectin, activities of polygalacturonase, endo-glucanase, cellobiohydrolase, and xylanase, and gene expressions of PG, EG2, PAL1, PAL3, and CAD5. Identifying molecular mechanisms underlying the differences in FF is useful for fundamental research and crop improvement in future.

The effect of high humidity hot air impingement blanching on the changes in cell wall polysaccharides and phytochemicals of okra pods.

Okra pods contain heat-sensitive substances, such as phenolic compounds and other phytochemicals that can be degraded when okra pods are subjected to heat treatment. The understanding of the impact of high humidity hot air impingement blanching (HHAIB) on the changes in physicochemical properties of polysaccharides and phytochemicals of okra pods is of great importance because over-blanching may result in cell membrane disruption and changes in biologically active compounds under prolonged exposure to the thermal treatment. Therefore, the present study aimed to investigate the effect of HHAIB on the changes in physicochemical properties of pectins and phytochemicals extracted from okra pods. Both the HHAIB time and method of extraction influenced their physicochemical characteristics and biological activity. Pectin fractions subjected to HHAIB were composed of polygalacturonic acid, rhamnogalacturonan, glucomannan, galactan, mannose, arabinose, rhamnose, calcium pectate and arabinogalactan. The contents of total phenolics, total flavonoids and antioxidant activity of extracts mostly increased during HHAIB (i.e. up to 19.0%, 13.2% and 35.3%, respectively). However, HHAIB reduced the chlorophyll-a (up to 55.7%) and lycopene (up to 52.6%) contents of okra pods. The acquired knowledge may be useful for better understanding and optimization of technologies based on HHAIB treatment. The HHAIB treated okra can be a promising natural alternative in different applications, including its use as a replacement of some ingredients in food or non-food systems as a result of richness in polysaccharides and polyphenols, as well as high antioxidant properties. © 2022 Society of Chemical Industry.

Changes in cell wall polysaccharides and quality of strawberry fruits from summer to autumn

Changes in cell wall polysaccharides and quality of strawberry fruits from summer to autumn

Elongating maize root: zone-specific combinations of polysaccharides from type I and type II primary cell walls

The dynamics of cell wall polysaccharides may modulate the cell wall mechanics and thus control the expansion growth of plant cells. The unique composition of type II primary cell wall characteristic of grasses suggests that they employ specific mechanisms for cell enlargement. We characterized the transcriptomes in five zones along maize root, clustered the expression of genes for numerous glycosyltransferases and performed extensive immunohistochemical analysis to relate the changes in cell wall polysaccharides to critical stages of cell development in Poaceae. Specific patterns of cell wall formation differentiate the initiation, realization and cessation of elongation growth. Cell walls of meristem and early elongation zone represent a mixture of type I and type II specific polysaccharides. Xyloglucans and homogalacturonans are synthesized there actively together with mixed-linkage glucans and glucuronoarabinoxylans. Rhamnogalacturonans-I with the side-chains of branched 1,4-galactan and arabinan persisted in cell walls throughout the development. Thus, the machinery to generate the type I primary cell wall constituents is completely established and operates. The expression of glycosyltransferases responsible for mixed-linkage glucan and glucuronoarabinoxylan synthesis peaks at active or late elongation. These findings widen the number of jigsaw pieces which should be put together to solve the puzzle of grass cell growth.

Hybrid Label-Free Molecular Microscopies for Simultaneous Visualization of Changes in Cell Wall Polysaccharides of Peach at Single- and Multiple-Cell Levels during Postharvest Storage.

Softening of fruit during the postharvest storage, which is mainly associated with both compositional and spatial changes of polysaccharides within cell wall, affects the texture and quality of fruit. Current research on the fruit softening mechanism lacks an understanding of the overall softening at the cell level. The objective of this work was to investigate the change in the spatial distribution of cell wall polysaccharides in peach flesh cells at both single- and multiple-cell levels in a label-free way during the postharvest storage. Nonmelting peaches (Prunus persica L. Batsch cv.”Zhonghuashoutao”) at commercial maturity were stored at 0 °C and 20 °C. Firmness measurement and chemical analysis were performed at each storage time. In addition, three molecular imaging techniques, namely confocal Raman microspectroscopy (CRM), Fourier transform infrared microspectroscopy (FTIRM), and stimulated Raman scattering microscopy (SRS) were used to visualize changes in the spatial distribution of cell wall polysaccharides of peach fruit in a label-free way during the postharvest storage. The combination of CRM and FTIRM provided complementary spectral information to visualize the spatial changes of cellulose, hemicellulose, and pectin in the cell wall of peach flesh during softening at the single-cell level, and found that the cell wall polysaccharides tended to be concentrated in the cell corner of parenchymal cells at the late stage. Furthermore, SRS, which is an ultrafast Raman imaging technique (approximately three or four orders of magnitude faster than CRM), was used for high-throughput cell wall phenotypes measurement. Different degradation degrees of parenchymal cells during fruit softening were found based on the gray-scale statistical analysis of SRS data. In general, cell wall polysaccharides decreased during softening and tended to be concentrated in the cell corner for most parenchymal cells at the late stage, but there were also some cells not in line with the whole softening trends. The results show that there were differences in the content and spatial changes of cell wall polysaccharides among parenchymal cells of peach fruit during the softening process, and the hybrid use of CRM, FTIRM, and SRS is a promising method for simultaneous visualization of changes in cell wall polysaccharides of peach.

Changes in metabolism of cell wall polysaccharides in oat leaves during senescence: relevance to the senescence-promoting effect of methyl jasmonate

Changes in cell wall polysaccharides in oat (Avena sativa L.) leaf segments during senescence promoted by methyl jasmonate (JA-Me) were studied. During the incubation with water at 25 °C in the dark, the loss of chlorophyll of the segments excised from the primary leaves of 8-day-old green seedlings was found dramatically just after leaf excision, and leaf color completely turned to yellow after the 3- to 4-day incubation in the dark. Application of 10 µM JA-Me substantially promoted the loss of chlorophyll corresponding with the chloroplast degradation. Cell wall polysaccharides in oat leaf segments mainly consisted of hemicellulosic and cellulosic ones. During the process of leaf senescence, the amount of hemicellulosic I and II, and cellulosic polysaccharides decreased, but little in pectic polysaccharides. JA-Me significantly enhanced the decrease in cellulosic polysaccharides, but little in hemicellulosic ones. Arabinose, xylose and glucose were identified as main constituents of neutral sugars of hemicellulosic polysaccharides. The neutral sugar compositions of hemicellulosic polysaccharides changed little during leaf senescence both in the presence or absence of JA-Me. These facts suggest that JA-Me affects sugar metabolism relating to cellulosic polysaccharides during leaf senescence.

Effects of an exogenous xylanase gene expression on the growth of transgenic rice and the expression level of endogenous xylanase inhibitor gene RIXI

Xylanases have attracted considerable interest in recent years owing to their various applications in industry and agriculture. The use of transgenic plants to produce xylanases is a less expensive alternative to biotechnological programmes. The aim of this study was to elucidate whether introducing a foreign xylanase gene ATX into rice had any adverse effect on plant growth and development. A recombinant xylanase gene ATX was introduced into rice variety Zhonghua 11 through Agrobacterium-mediated transformation. The T₂ generation of transgenic rice was compared with the control (non-transgenic plants). Exogenous xylanase gene ATX was expressed in rice, and all examined transgenic lines exhibited xylanase activity. The transgenic lines (T₂, 'X1-3' and 'X2-5') appeared to grow and develop normally. There were no differences in net photosynthetic rate between transgenic rice lines ('X1-3' and 'X2-5') and wild type (WT) rice plants at the heading/flowering stage. Xylanases are key enzymes in the degradation of plant cell walls. Cell wall composition analysis showed that that there were no changes in cell wall polysaccharides in the root apex but some alterations in leaves in transgenic rice plants. The results also showed that the expression of exogenous xylanase gene ATX in rice would increase the expression of endogenous xylanase inhibitor gene RIXI, which could play a role in plant defence. Thus the stress resistance of transgenic rice plants might be improved. Exogenous xylanase gene ATX could be successfully expressed in rice, and the exogenous protein had no apparent harmful effects on growth and development in transgenic rice plants.

Compositional changes in cell wall polysaccharides from apple fruit callus cultures modulated by different plant growth regulators

The cell wall composition of apples callus cultures showed changes in the presence of 5mgl−1 of three different plant growth regulators (PGRs), namely picloram, abscisic acid and gibberellic acid. Although the structural functions of cell walls do not generally allow for pronounced variations of the total pectin and matrix glycan content, this work provides evidence that the addition of these plant growth regulators can rule, at least partly, cell wall metabolism in apple callus cultures. The chelator- and carbonate-extracts always had the analytical characteristics of pectins, with high proportions of uronic acids, arabinose and galactose as the main monosaccharides, and a significant proportion of rhamnose, but the cross-linking glycan fractions were still rich in RG-I-like material. The application of PGRs produced shifts of uronic acid and neutral sugars between fractions. Arabinose was the neutral sugar exhibiting more variations in apple callus cell wall. Picloram and abscisic acid produced an increase of the uronic acid contents of the cell walls. The AIRs obtained from calluses treated with different PGRs did not show large amounts of high molecular weight products, as determined by size-exclusion chromatography. For the carbonate-extract only the callus treated with picloram displayed two separated peaks for products of different molecular weights. The chromatographic profiles for the 4% KOH-extract displayed two peaks for all the treatments, one very sharp with high molecular weight, and another one wider of smaller molecular weight, whereas the difference between treatments can only be appraised through the areas of the peaks. This is the first report on cell wall composition from fruit calluses supplemented with different PGRs.

Changes in cell wall polysaccharides and cell wall degrading enzymes during ripening of Fragaria chiloensis and Fragaria ×ananassa fruits

Chilean strawberry ( Fragaria chiloensis ) is arising as a new fruit crop that can diversify the world supply of berries. Fruit softening is thought to be linked to an extensive modification of pectin and hemicellulosic cell wall fractions which in turn is determined to a great extent by the action of some cell wall-modifying enzymes. The objective of this work was to compare cell wall changes and the enzyme activities of pectin methylesterase (PME), polygalacturonase (PG), endoglucanase (EGase), α-arabinofuranosidase (AFase), β-galactosidase (βGal), and β-xylosidase (βXyl) between F. chiloensis and Fragaria × ananassa (cv. Chandler) at three fruit developmental stages: large green (LG), turning (T) and ripe (R). A rapid decrease in fruit firmness between LG and T stages was observed in both species; nevertheless firmness reduction in F. chiloensis was steeper than in F . × ananassa . This could be related to a faster loss of HCl-soluble polymers (HSP fraction) presented in F. chiloensis fruit. However, commercial F . × ananassa showed a greater depolymerization of HSP polymers than F. chiloensis . With the exception of PME, the activity of all assayed enzymes was higher in F. chiloensis than in F . × ananassa fruits. The role of PG and EGase seems to be central in both species: these enzymes are correlated to the decrease in the content of HSP and NaOH-soluble polymers (NSP fraction), respectively. In addition, activity levels of βGal and βXyl were significantly correlated with fruit firmness reduction in F. chiloensis and F. × ananassa , respectively.

Compositional Changes in Cell Wall Polysaccharides from Japanese Plum (Prunus salicina Lindl.) during Growth and On-Tree Ripening

Climacteric Japanese plums were harvested at six developmental stages with no intermediate storage period, and cell wall compositional changes were analyzed. Arabinose proved to be the principal neutral monosaccharide constituent in cell walls during growth and the most dynamic neutral sugar in pectic fractions. Arabinose loss from tightly bound pectins was found to be a relatively early feature in the sequence of cell wall biochemical modifications, thus suggesting a softening-related role during Japanese plum on-tree ripening. Depolymerization of matrix glycans started at the end of the cell expansion phase and increased throughout ripening. Pectin solubilization was first detected during early ripening. Firmness loss did not correlate with polyuronide depolymerization early in ripening, but the last softening phase was associated with a strong depolymerization of cell wall polyuronides as well as a decrease in the arabinose/galactose ratio in loosely bound pectins. This is the first work that characterizes the temporal sequence of cell wall polysaccharide changes in Japanese plum.

Changes in Cell Wall Polysaccharides and Hydroxycinnamates in Wheat Roots by Aluminum Stress at Higher Calcium Supply

ABSTRACT The present study was conducted to investigate the cell-wall polysaccharides and hydroxycinnamates in wheat plants (Triticum aestivum L.) under aluminum (Al) stress at a higher level of calcium (Ca) supply. Seedlings were grown in nutrient solution for 7 d and then subjected to treatment solutions containing Al (0 or 100 μM) and Ca (0 or 2500 μM) in a 500 μM CaCl 2 solution at pH 4.5 for 8 d. Calcium treatment (2500 μM) improved root growth significantly under Al-stress conditions. The contents of pectin and hemicellulose in roots were increased under Al-stress conditions, and this increase was conspicuous in the hemicellulosic fraction. The increase in the hemicellulose was attributed to increases in arabinose, xylose, and glucose in neutral sugars. High Ca treatment decreased these contents in Al-stressed cell walls. Aluminum treatment increased the content of ferulic acid, whereas Ca treatment with Al reduced the content. These results suggest that Al may modify the mechanical properties of cell-wall polysaccharides by enhancing the synthesis of arabinoxylan, β-glucan, and ferulic acid in the cell wall. High Ca treatment may maintain the normal synthesis of these materials even under Al-stress conditions.

Distribution of Accumulated Aluminum and Changes in Cell Wall Polysaccharides in Eucalyptus camaldulensis and Melaleuca cajuputi under Aluminum Stress

Distribution of aluminum (Al) within plant components and Al-induced changes in cell wall polysaccharides in root tips of Eucalyptus camaldulensis Dehnh. seedlings were compared with those of Melaleuca cajuputi Powell. In E. camaldulensis, 0.5 mM Al (pH 4.2 for 40 d) reduced plant dry weight by 50%, increased callose concentration in the root tips and induced leaf necrosis. In comparison with M. cajuputi, Al concentrations were higher in roots and leaves of E. camaldulensis on both a fresh weight basis and in the cell sap, but were lower in the cell wall. Al increased pectin, hemicellulose and cellulose concentration in the cell walls of E. camaldulensis root tips. Al-induced leaf necrosis and growth reduction in E. camaldulensis is discussed in the context of potentially toxic concentrations of Al in plant tissue and changes in polysaccharide content which could reduce water and nutrient uptake and cell wall extensibility in roots.

Alterations in cell wall polysaccharides during ripening in distinct anatomical tissue regions of the fig (Ficus carica L.) fruit

Abstract During the last stage of fig ( Ficus carica L.) fruit development, profound cell wall modification processes occur as indicated by increase in fruit size and tissue softening. In this study, we characterized the changes in cell wall polysaccharides taking place within the distinct and separate tissues of the receptacle and the pulpy drupelets during sequential ripening in fig fruit. The pectic extracts had high uronic acid contents in addition to high amounts of Ara, Gal and Rha. The gel filtration profile of the water-soluble polymers at the ripening onset in drupelets were different when compared to those of the receptacle, even though in both tissues, these polymers underwent increased solubilization and depolymerization during ripening. The molecular downshift of the CDTA-soluble polymers and the decrease in the amounts of both the uronic acid and total sugars were more pronounced in the drupelets than in the receptacle. Major difference in the neutral sugar composition between the two tissues was only observed in the Na 2 CO 3 -soluble fraction. The xyloglucan polymers in 4% KOH fraction exhibited a molecular size downshift accompanied by a decline in Xyl and increase in Glc. In the 24% KOH fractions of both tissues, the total sugar and xyloglucan components decreased in amount and also exhibited a molecular size downshift during ripening. These data suggest that even though quantitative and qualitative changes in cell wall polysaccharides occurred during ripening in both tissues, qualitative variations between tissues occurred only in the pectic polymers but not in the hemicellulosic polymers.

Changes in Cell Wall Polysaccharides and Physical Properties of Peach (Prunus persica Batsch) Fruit during Ripening

Changes in cell wall polysaccharides and physical properties, associated with the ripening of the peach (Prunus persica Batsch) fruit, were characterized. Enzymically inactivated cell walls were prepared from mesocarps of peach fruit harvested periodically. Pectin-associated and hemicellulose- associated polysaccharides were extracted from the cell walls sequentially, and neutral sugar and uronic acid contents in each fraction were determined. Each fraction was then analyzed for its neutral sugar composition by gas-liquid chromatography (GLC). The fractionated polysaccharides were applied to a column of Sepharose CL-4B gel (1.5 × 40 cm) to estimate the molecular weight distribution. The amount of the uronic acid content in water fraction increased dramatically at the over-ripe stage, whereas xyloglucan, a dominant constituent of hemicellulose, gradually degraded throughout the fruit softening period. These data suggest that peach fruit softening involves the following two processes: initially, xyloglucan degrades during which the pectin remains insoluble; secondly pectin becomes soluble concurrently with continues to xyloglucan degradation. These two processes of maturation correspond to the changes of two parameters on the physical properties, determined by the conventional stress relaxation method. Moreover we determined the degree of methyl esterification (DOM) of the pectin in the crude cell wall extract to investigate its property. Based on our results, we discuss the structure of the cross-linkages among the cell wall polymers and those enzymes involved in fruit softening.

ウメ果実の成熟に伴う果皮および果肉中の細胞壁多糖類の変化

ウメ果実の成熟に伴う果皮および果肉中の細胞壁多糖類の変化