Search

Lignin is an abundant phenolic polymer present in plant cell walls that aids water transport and plays crucial roles in protecting plants from environmental stresses. There is a growing interest in lignin as a potential source of sustainable bioproducts, including bioplastics, chemicals, carbon materials, and biofuels. The aim of modeling lignin metabolism is to predict the dynamics of lignin synthesis to facilitate plant genetic engineering strategies and ultimately improved lignin utilization. Recurring challenges associated with this goal are the lack of an integrated understanding of the lignin biosynthetic network and acquiring reliable metabolic data with cellular and subcellular resolution. While genome-scale metabolic models have been developed in microbial systems, their use in plants remains challenging due to their compartmentalized metabolism and cross-communication between organelles. Plant biomass contains lignin that can be converted into high-value-added chemicals, fuels, and materials. The precise genetic manipulation of lignin content and composition in plant cells offers substantial environmental and economic benefits. However, the intricate regulatory mechanisms governing lignin formation challenge the development of crops with specific lignin profiles. Mathematical models and computational simulations have recently been employed to gain fundamental understanding of the metabolism of lignin and related phenolic compounds. This review article discusses the strategies used for modeling plant metabolic networks, focusing on the application of mathematical modeling for flux network analysis in monolignol biosynthesis. Furthermore, we highlight how current challenges might be overcome to optimize the use of metabolic modeling approaches for developing lignin-engineered plants. [ABSTRACT FROM AUTHOR]

Understanding plant reproduction offers potential routes both to impact on seed crop agriculture and to reveal key principles of plant cell signalling. Cell–cell signalling during plant reproduction revolves around the interactions between a small family of receptor-like kinases, their coreceptors, and ligands. Several specific peptides and carbohydrates have recently been confirmed as ligands in reproductive signalling, opening new avenues to investigate their interactions and potentially distinct downstream effects. Known downstream signalling responses include the production of reactive oxygen species, the generation of specific calcium signatures, and changes to the cell wall. Plant reproduction is a complex, highly-coordinated process in which a single, male germ cell grows through the maternal reproductive tissues to reach and fertilise the egg cell. Focussing on Arabidopsis thaliana , we review signalling between male and female partners which is important throughout the pollen tube journey, especially during pollen tube reception at the ovule. Numerous receptor kinases and their coreceptors are implicated in signal perception in both the pollen tube and synergid cells at the ovule entrance, and several specific peptide and carbohydrate ligands for these receptors have recently been identified. Clarifying the interplay between these signals and the downstream responses they instigate presents a challenge for future research and may help to illuminate broader principles of plant cell–cell communication. [ABSTRACT FROM AUTHOR]

Cadmium (Cd), a widely distributed and highly toxic heavy metal, poses a severe threat to soil fertility and plant growth. Citric acid (CA), a small organic acid molecule, plays a crucial role in alleviating heavy metal toxicity in plants. However, the specific mechanism underlying how CA organizes and mitigates the damage caused by heavy metals to plant cells remains unclear. Therefore, we studied the impact of exogenous CA on Cd-induced stress in Iris tectorum. The results showed that the addition of exogenous CA significantly increased the activity of antioxidant enzymes and altered the content of mineral elements including Fe, Zn, Ca, and Mn. Notably, compared to the Cd-only treatment, the proportion of Cd in the root cell walls increased by 14% in the presence of CA, and this increase was due to the ability of CA to regulate the amount of polysaccharide components in the root cell walls. CA affected the activity of pectinesterase (PME), changed the degree of pectinesterification (PMD), and enhanced the root cell walls' ability to bind Cd, thereby reducing the Cd content in the above-ground tissues and alleviating heavy metal toxicity in plants. In summary, this study provides robust evidence that supports the use of CA to improve the efficiency of urban soil remediation. [Display omitted] • Exogenous CA alleviated the toxic effects of Cd on I. tectorum. • Compartmentalizing Cd mitigated Cd toxicity effects. • Pectin and PMD in the root cell walls were key to alleviating Cd toxicity. • CA changed the mineral elements content to maintain normal plant development. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chickpea cell wall integrity affects starch bioaccessibility, digestion, and postprandial metabolism. •.Preserving cellular structure of processed chickpeas improves blood glucose homeostasis. •.Rheological tests provide insight of chickpea hummus properties for future studies of amylolysis. Slowing the rate of carbohydrate digestion leads to low postprandial glucose and insulin responses, which are associated with reduced risk of type 2 diabetes. There is increasing evidence that food structure plays a crucial role in influencing the bioaccessibility and digestion kinetics of macronutrients. The aims of this study were to compare the effects of two hummus meals, with different degrees of cell wall integrity, on postprandial metabolic responses in relation to the microstructural and rheological characteristics of the meals. A randomised crossover trial in 15 healthy participants was designed to compare the acute effect of 27 g of starch, provided as hummus made from either intact chickpea cells (ICC) or ruptured chickpea cells (RCC), on postprandial metabolic responses. In vitro starch digestibility, microstructural and rheological experiments were also conducted to evaluate differences between the two chickpea hummus meals. Blood insulin and GIP concentrations were significantly lower (P < 0.02, P < 0.03) after the consumption of the ICC meal than the meal containing RCC. In vitro starch digestion for 90 min was slower in ICC than in RCC. Microscopic examination of hummus samples digested in vitro for 90 min revealed more intact chickpea cells in ICC compared to the RCC sample. Rheological experiments showed that fracture for ICC hummus samples occurred at smaller strains compared to RCC samples. However, the storage modulus for ICC was higher than RCC, which may be explained by the presence of intact cells in ICC. Food structure can affect the rate and extent of starch bioaccessibility and digestion and may explain the difference in the time course of metabolic responses between meals. The rheological properties were measured on the two types of meals before ingestion, showing significant differences that may point to different breakdown mechanisms during subsequent digestion. This trial was registered at clinicaltrial.gov as NCT03424187. [ABSTRACT FROM AUTHOR]

Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), mainly transmitted through droplets to infect the lungs, and seriously affecting patients' health and quality of life. Clinically, anti-TB drugs often entail side effects and lack efficacy against resistant strains. Thus, the exploration and development of novel targeted anti-TB medications are imperative. Currently, protein-protein interactions (PPIs) offer novel avenues for anti-TB drug development, and the study of targeted modulators of PPIs in M. tuberculosis has become a prominent research focus. Furthermore, a comprehensive PPI network has been constructed using computational methods and bioinformatics tools. This network allows for a more in-depth analysis of the structural biology of PPIs and furnishes essential insights for the development of targeted small-molecule modulators. Furthermore, this article provides a detailed overview of the research progress and regulatory mechanisms of PPI modulators in M. tuberculosis , the causative agent of TB. Additionally, it summarizes potential targets for anti-TB drugs and discusses the prospects of existing PPI modulators. [Display omitted] [ABSTRACT FROM AUTHOR]

Starch is the major stored carbohydrate in grains and legumes. Apart from nutritional functionality, starch has multiple industrial applications. Starch is synthesised in plant cells along with proteins, lipids, and polyphenols. These macromolecules interact both in planta as well as during downstream processing, e.g., extraction of starch. Whilst the interaction of starch with protein, lipids, and other hydrocolloids during processing is widely reported, the in planta interactions and their effect on food and nutritional functionality is mostly overlooked. This review provides an overview of mechanisms of interaction of starch with protein, lipids, and polyphenols in planta and the effect of these interactions on food processing as well as human nutrition. The interaction of starch with other macronutrients as well as polyphenols are described at the granular level as well as at the cellular level and presented in a schematic model (Fig. 1). The granular level interactions such as with surface and internal protein and lipids associated with granules, extra-granular storage proteins and formation of amylose-lipid and polyphenol complexes primarily affect the processing functionality of starch, whereas cellular level interactions and encapsulation enhance nutritional functionality of starch in terms of lowering the metabolic responses from energy dense nutrients. Thus, consideration of in planta interactions among macronutrients as well as with cell walls is important during processing, in both selection of ingredients as well as the formulation of foods. Image 1 • Starch interacts with proteins, lipids, phytochemicals and cell walls in planta. • In planta interactions affect the functional and nutritional properties of starch. • Intact cellular structures conserve interactions and nutritional functionality. [ABSTRACT FROM AUTHOR]

Highlights • Storage proteins in cotyledon cells act as a barrier to starch digestion in-vitro. • Molecular confinement within cells limits protein thermal denaturation. • Cotyledon cell integrity limits the rate and extent of protein digestion in-vitro. • Starch granules within cotyledon cells do not affect the rate of protein digestion. Abstract Cotyledon cells in kidney beans naturally encapsulate starch and proteins limiting the access of digestive enzymes to their substrates. In this study, we investigated the effect of cell wall on bean protein digestibility and its relationship with starch digestion. Results showed that proteins contained in the cytoplasmic matrix influence the rate at which starch is digested in-vitro. Confocal laser scanning microscopy revealed that storage proteins in the cytoplasm act as a second encapsulation system preventing starch digestion. This microstructural organization only affected starch since no changes in protein digestion rate or extent were observed due to the presence of starch granules. Fourier transform infrared spectroscopy revealed that cellular entrapment limited protein denaturation induced by thermal treatments. High concentrations of a fraction resistant to digestion were found in proteins that were heated when entrapped within intact cotyledon cells, compared to those thermally treated as bean flour. [ABSTRACT FROM AUTHOR]

Highlights • Phenolic extraction followed in wines made from Shiraz grapes of different ripeness degree. • As fermentation progressed more phenolics extracted in wines made from riper grapes. • Cell wall polysaccharide deconstruction was a determining factor for phenolic extractability. Abstract This study evaluated the relationship between cell wall breakdown, from Shiraz grapes harvested at three different ripeness levels and the colour and phenolics extracted during alcoholic fermentation into wines. Phenolic differences between the ripeness treatments were minimal after ¼ of the fermentation was completed. However, colour and phenolic content were significantly higher in finished wines made from 25°Brix grapes compared to those from 21°Brix and 23°Brix. Levels of grape cell wall polysaccharide deconstruction during fermentation was a determining correlative factor in relation to phenolic extractability. In this context, the de-pectination observed during ripening was found to enhance this deconstruction or "opening-up" of the grape pomace during fermentation, thus increasing the differential extraction of specific polyphenols, especially polymeric polyphenols, into the wines. Additionally, the degree of cell wall deconstruction seemed to play a role in the possible retention and extraction of specific grape proanthocyanidins, depending on their nature and polymer length. [ABSTRACT FROM AUTHOR]

Highlights • Phenolic and polysaccharide compositions of Shiraz grapes and wine were investigated. • Vintage and ripening both influenced polysaccharide and phenolic composition in the grapes. • Grape berry intactness was influenced by the cell wall composition. Abstract Phenolic compounds play an important role in colour stability and sensory properties of red wine. This study evaluated berry skin cell wall composition and how this influences grape and wine phenolics at different ripeness levels (21°Brix, 23°Brix, and 25°Brix) over two consecutive vintages. The vintage effect was highly significant, especially in the pectin fraction of the grape cell walls and affected the concentrations of certain phenolics extracted. The climatic variance between the seasons might have influenced the differences observed in the grape cell wall compositions. Firstly, a higher grape and wine phenolic content, especially in polymeric phenols, was found in 2015 wines. Additionally, grape berry cell walls, especially at the earliest stages of ripening, were found to be more intact in 2015 than in 2016. Thus, a possible relationship was found between the degree of berry intactness, especially for pectin-rich components, and the corresponding phenolic extractability during the winemaking. [ABSTRACT FROM AUTHOR]

Abstract We investigated the effects of elevated ozone (O 3) concentration on leaf nitrogen (N), a key determinant of plant photosynthesis, with two clones of poplar grown in open-top chambers. We focus on the difference between mass-based leaf N concentration (N mass) and area-based one (N area) in their responses to elevated O 3 , and the allocation of N to different leaf components: photosynthetic apparatus, cell walls, and others under elevated O 3 level. Our results showed that elevated O 3 significantly increased N mass , but reduced N area and leaf mass per area (LMA). The two clones showed no difference in N mass response to O 3 , but the more sensitive clone showed greater reduction of N area and LMA due to O 3. We also found positive relationships between N area and photosynthetic parameters, e.g. light-saturated photosynthetic rate (A sat). Furthermore, elevated O 3 significantly reduced photosynthetic N-use efficiency (PNUE) and leaf N allocation to photosynthetic components, while increasing N allocation to cell walls and other components. We concluded that plants invested more N in cell walls and other components to resist O 3 damages at the expense of photosynthetic N. The change of N allocation in plant leaves in response to elevated O 3 could have an impact on ecological processes, e.g. leaf litter decomposition. Graphical abstract Unlabelled Image Highlights • Ozone exposure-response relationships for leaf N concentration were established. • E-O 3 increased N mass of leaf, but reduced N area. • E-O 3 reduced leaf N allocation to photosynthesis (productivity). • E-O 3 increased leaf N allocation to cell walls (defense). [ABSTRACT FROM AUTHOR]

Abstract The role of the cell wall in short-term Ni uptake at different solution Ni levels was investigated in mung bean (Vigna radiata (L.) R. Wilczek) and wheat (Triticum aestivum L., cv. Inna). Both Ni-binding capacity of the CWs and roots are lower for wheat than for mung bean at all Ni levels in the solution. For both plants amounts of Ni associated with roots and root cell walls increased with Ni concentration. The contribution of CWs to Ni absorption by roots depends on Ni level in the medium and plant species. The Ni accumulated in CWs could account for total Ni content of roots (except for wheat in highest Ni treatment). Besides, mung bean plants employ the strategy of reducing Ni accumulation in the root CWs during exposure to excess but not toxic solution Ni level. According to the results, predominant Ni binding in the apoplast of mung bean and wheat roots is observed at both high and low external Ni, which suggests that apoplastic pathway is the main means of Ni transport in the root cortex of these species. [ABSTRACT FROM AUTHOR]

The constitution and forms of rice determine its processing and cooking properties and further control the cooked rice quality. As the two main components, starch and protein content correlations and their characteristics have been extensively explored. However, rice is mainly consumed as polished kernels, components distribution, cytoplasmic matrix, and cell walls work together, and the properties of extracted components or flour are difficult to reflect the quality of cooked rice accurately. Thus, this review summarizes the multi-scale structure changes of main components during real rice cooking conditions. The dynamic thermal changes and leaching behaviors in rice kernels are compared with pure starch or rice flour. The in situ changes and interactions of starch granules, protein bodies, and cell walls during cooking are reviewed. Based on this, different textural evaluation methods are compared, and the advantages and disadvantages are pointed out. The oral chewing perception and bionic chewing simulation for textual evaluation have gradually become hot. Both rice quality controllers and eating quality evaluators attempt to establish an accurate quality evaluation system with the increased demand for high-quality rice. [ABSTRACT FROM AUTHOR]

Cooked whole pulses are widely accepted as a low glycemic food with potential health benefits of reducing the risk of obesity and type 2 diabetes. However, the structural basis for the variation in digestion rate and extent of different pulses is still unclear. In this study, intact cotyledon cells of four commercial pulses (i.e., pinto bean, garbanzo bean, green-split pea, and black-eyed pea) were isolated under controlled cooking and isolation conditions, as a model for whole foods. We investigated the macrostructure of intact cells and structural features of entrapped starch granules, such as crystallinity and thermal parameters, and diffusion of an amylase-sized FITC dextran probe into intact cells. In vitro digestion kinetic profiles of pulse cells were monitored by a reducing sugar assay with a fixed α-amylase activity, and were fitted into a first order model to obtain the apparent rate coefficient and digestion extent at 180 min. Pearson's correlation analysis suggested that there is no significant correlation between the kinetic parameters and structural features of entrapped starch granules nor the size of the cell particles. It is concluded that the starch digestibility of isolated pulses is controlled by the accessibility of digestive enzymes, which is limited by the rigid cell wall and/or pulse protein matrix, rather than starch structure. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus biofilms pose a serious clinical threat as reservoirs for persistent infections. Despite this clinical significance, the composition and mechanism of formation of S. aureus biofilms are unknown. To address these problems, we used solid-state NMR to examine S. aureus (SA113), a strong biofilm-forming strain. We labeled whole cells and cell walls of planktonic cells, young biofilms formed for 12–24 h after stationary phase, and more mature biofilms formed for up to 60 h after stationary phase. All samples were labeled either by (i) [ 15 N]glycine and l -[1- 13 C]threonine, or in separate experiments, by (ii) l -[2- 13 C, 15 N]leucine. We then measured 13 C- 15 N direct bonds by C{N} rotational-echo double resonance (REDOR). The increase in peptidoglycan stems that have bridges connected to a surface protein was determined directly by a cell-wall double difference (biofilm REDOR difference minus planktonic REDOR difference). This procedure eliminates errors arising from differences in 15 N isotopic enrichments and from the routing of 13 C label from threonine degradation to glycine. For both planktonic cells and the mature biofilm, 20% of pentaglycyl bridges are not cross-linked and are potential surface-protein attachment sites. None of these sites has a surface protein attached in the planktonic cells, but one-fourth have a surface protein attached in the mature biofilm. Moreover, the leucine-label shows that the concentration of β-strands in leucine-rich regions doubles in the mature biofilm. Thus, a primary event in establishing a S. aureus biofilm is extensive decoration of the cell surface with surface proteins that are linked covalently to the cell wall and promote cell-cell adhesion. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is a major and dangerous human pathogen that causes a range of clinical manifestations of varying severity, and is the most commonly isolated pathogen in the setting of skin and soft tissue infections, pneumonia, suppurative arthritis, endovascular infections, foreign-body associated infections, septicemia, osteomyelitis, and toxic shocksyndrome. Honokiol, a pharmacologically active natural compound derived from the bark of Magnolia officinalis , has antibacterial activity against Staphylococcus aureus which provides a great inspiration for the discovery of potential antibacterial agents. Herein, honokiol derivatives were designed, synthesized and evaluated for their antibacterial activity by determining the minimum inhibitory concentration (MIC) against S. aureus ATCC25923 and Escherichia coli ATCC25922 in vitro . 7c exhibited better antibacterial activity than other derivatives and honokiol. The structure-activity relationships indicated piperidine ring with amino group is helpful to improve antibacterial activity. Further more, 7c showed broad spectrum antibacterial efficiency against various bacterial strains including eleven gram-positive and seven gram-negative species. Time-kill kinetics against S. aureus ATCC25923 in vitro revealed that 7c displayed a concentration-dependent effect and more rapid bactericidal kinetics better than linezolid and vancomycin with the same concentration. Gram staining assays of S. aureus ATCC25923 suggested that 7c could destroy the cell walls of bacteria at 1 × MIC and 4 × MIC. [ABSTRACT FROM AUTHOR]

Isolated bean cells were used to understand the contribution of cell wall and cytoplasmic matrix on starch digestibility. Cotyledon cells were treated enzymatically and mechanically to reduce the level of cell intactness. SEM and chemical characterization revealed that enzymatic treatment modified cell wall thickness and porosity without altering the cytoplasmic matrix, whereas mechanical treatment completely disrupted cell structure. Decreasing cell intactness increased the rate but not the extent of starch digestion in-vitro . It was concluded that cell wall serves as a permeable barrier limiting the access of digestive enzymes. Cytoplasmic matrix, on the other hand, reduced further the accessibility of amylase to starch affecting its hydrolysis rate. In addition, it was proven that cell structural changes, if any, occurring during digestion had no effect on starch hydrolysis. [ABSTRACT FROM AUTHOR]

Lactococcus cremoris and Lactococcus lactis are among the most extensively exploited species of lactic acid bacteria in dairy fermentations. The cell wall of lactococci, like other Gram-positive bacteria, possesses a thick peptidoglycan layer, which may incorporate cell wall polysaccharides (CWPS), wall teichoic acids (WTA), and/or lipoteichoic acids (LTA). In this study, we report the isolation, purification and structural analysis of the carbohydrate moieties of glycolipids (GL) and LTA of the L. cremoris model strain 3107. Chemical structures of these compounds were studied by chemical methods, NMR spectroscopy and positive and negative mode ESI MS. We found that the LTA of strain 3107 is composed of short chains of 1,3-polyglycerol phosphate (PGP), attached to O-6 of the non-reducing glucose of the kojibiose-Gro backbone of the glycolipid anchor. Extraction of cells with cold TCA afforded the detection of 1,3-glycerol phosphate chains randomly substituted at O-2 of glycerol by D -Ala. Unlike the LTA of L. lactis strains studied to date, the PGP backbone of the LTA of L. cremoris 3107 did not carry any glycosyl substitution. The deacylated glycolipid fraction contained the free kojibiose-Gro oligosaccharide, identical to the backbone of the GL anchor of LTA, and its shorter fragment α-Glc-1-Gro. These OS may have originated from the GL precursors of LTA biosynthesis. [Display omitted] • Lipoteichoic acid (LTA) from Lactococcus cremoris was studied. • LTA consists of polyglycerol phosphate, substituted with d -alanine. • Chain anchor consists of kojibiose-glycerol. • Structure is similar to Streptococcus and L. lactis LTA. [ABSTRACT FROM AUTHOR]

Glycome profiling allows for the characterization of plant cell wall ultrastructure via sequential extractions and subsequent detection of specific epitopes with a suite of glycan-specific monoclonal antibodies (mAbs). The data are often viewed as the amount of materials recovered and coinciding colored heatmaps of mAb binding are generated. Interpretation of these data can be considered qualitative in nature as it depends on detecting subtle visual differences in antibody binding strength. Here, we report a mixed model-based quantitative approach for glycome profile analyses, which accounts for the amount of materials recovered and displays the normalized values in revised heatmaps and statistical heatmaps depicting significant differences. The utility of this methodology was demonstrated on a previously published dataset investigating the effects of moisture stress on the roots and needles of Pinus taeda . An annotated R script for the quantitative methodology is included to allow future studies to utilize the same approach. [ABSTRACT FROM AUTHOR]

Plastic deformation of ARMCO iron processed by ECAP up to a maximum equivalent strain of sixteen (i.e., 1, 4, 8, and 16 ECAP passes) following route Bc was investigated by analyzing its microstructure and the stress-strain curves obtained after tensile tests at different levels of deformation. Three values of deformation (two in the plastic region taking into account the modified Crussard-Jaoul analysis and one after failure) were considered. Fractions of LAGB and HAGB, grain size and grain aspect ratio were calculated and compared for the different ECAP passes and tensile deformation levels. The dislocation density evolution calculated by the Bergström model for both the tensile curves and the ECAP curve showed a higher increase in the amount of dislocations during the initial stages of deformation than at higher values of deformation due to higher probabilities of dislocations annihilation. The strain hardening exponents calculated via the Bergström model for each ECAP pass shows that there is a continuous decrease in the strain hardening capacity until the eighth pass where a small increase with a subsequent stabilization was found. The dislocation densities calculated by the Estrin model presented a good correlation with values reported in bibliography for iron especially with those calculated by X-ray diffraction. This latter model predicted well the strain hardening evolution for stages III, IV and V for ARMCO iron processed by ECAP, where the main increments in hardening for stages IV and V were coming from the cell interiors. [ABSTRACT FROM AUTHOR]

The influence of the physical structure of cereal endosperm on the natural structural integrity (intact cells) and starch bioaccessibility of the resultant flours was studied using maize as example. Endosperm hardness, defined by its intracellular (protein matrix) and extracellular (cell walls) constituents, affected the granular and molecular damage of the starch of the resultant flours leading to higher digestibility of raw hard than soft endosperm flours, but comparatively lower digestibility after cooking. After milling, hard endosperm possessed more damaged starch (radial splitting of amylopectin clusters) in the periphery of the resultant particles that increased in vitro starch digestibility of raw flours. Conversely, the hard endosperm plant tissue matrix significantly limited water availability and heat transfer on starch gelatinisation, thereby decreasing the digestion rate after hydrothermal processing (in particle size flours >80 μm). This study provides a unique mechanistic understanding to obtain cereal flours with slow digestion property for commercial utilisation. [ABSTRACT FROM AUTHOR]

The physicochemical properties of blackberry cell walls under air drying with and without contact ultrasonication were analysed, and their ability to bind soluble phenolics was evaluated. Compared to air drying alone, ultrasound promoted cell wall shrinkage and reduced their specific surface area and water binding capacity. Meanwhile, the in-process ultrasound further increased the amount of water soluble pectin (WSP) and decreased protopectin. After drying, the cell walls of ultrasound-dried samples contained 11.6% less protopectin (PP) than air-dried samples. Pectins in ultrasound-dried samples were also more aggregated with a reduced branching degree of Rhamnogalacturonan-I (RG-I). Most of these ultrasonic modifications of blackberry cell walls hindered their phenolics acquirement. The equilibrium adsorption capacities of cell walls from ultrasound-dried blackberries for 1 h were 33.5% (for catechin) and 21.8% (for phloretic acid) lower than the counterparts from air-dried samples for 8 h. Although the soluble phenolics absorbed by dried blackberry cell walls were more thermal-stable than those adsorbed by fresh blackberry cell walls, the overall protection provided by cell walls was still regarded as attenuated with drying due to the decline in the adsorption ability. Besides, it is believed that the higher retention of soluble phenolics in ultrasound dried samples is ascribed to the shortened thermal-drying time rather than the cell walls-phenolics interactions. These findings provide an in-depth understanding of the effect of ultrasound drying on phenolic stability. [Display omitted] • Ultrasound reduced specific surface area and water binding capacity of cell walls. • Ultrasound increased the amount of water soluble pectin and decreased protopectin. • The ultrasound-intensified drying decreased the branching degree of RG-I pectin. • The ability of cell walls to absorb soluble phenolics was reduced after sonication. • The protections on soluble phenolics provided by cell walls weakened with drying. [ABSTRACT FROM AUTHOR]

Bamboo fibers have excellent mechanical properties, and as such are a popular raw material in papermaking, textile, and various high-tech industries. In this study, the longitudinal mechanical properties of Moso bamboo ( Phyllostachys Heterocycla Var. Pubescens) fiber cell walls during development were systematically investigated via nano-indentation technique at the sub-cellular level. Several influencing factors were also analyzed, particularly the effects of different locations within the vascular bundle and age. The results showed that the longitudinal nano-indentationmodulus (NI modulus) of the 1-month-old bamboo fiber cell walls was relatively high and changed very little in different locations of the vascular bundle, only fluctuating near 22 GPa, while that at the interface between fibers and parenchyma cells (i.e., the edge of the vascular bundle) was smaller and less stable (15.61 GPa on average); nano-indentation hardness (NI hardness) decreased from the center of the vascular bundle to the outside, ranging between 0.4665 and 0.5603 GPa. Age had no significant effect on NI modulus from 1 month to 36 months, while NI hardness did increase with age ( p < 0.05), showing mean values of 0.5452–0.6142 GPa across the samples. Our observations of longitudinal NI modulus and hardness were mainly affected by the microfibril angles and lignin content, respectively. These results may provide mechanical evidence for bamboo growth and lignin deposition, and also provide a scientific basis for the successful utilization of bamboo fibers. [ABSTRACT FROM AUTHOR]

Nanoplastics (NPs) have become an emerging global environmental problem, and the toxicity of polystyrene nanoplastics (PS-NPs) in rice plants has received widespread attention. However, few studies have focused on silicon (Si)-mediated interactions between PS-NPs and rice. Thus, two forms of Si (organosilicon/inorganic silica) treated rice cells were exposure of positively or negatively charged NPs, PS-NH 2 and PS-COOH, to evaluate the effects of Si for defense against PS-NPs toxicity in rice. The result showed PS-NH 2 nanoparticles were accumulated at relatively low levels in cells compared with that of PS-COOH, but induced a higher accumulation of hydrogen peroxide (H 2 O 2) and superoxide radicals (O 2 •−). However, both organosilicon and inorganic silica can generate more negative potential on the surfaces of cell wall to absorb large numbers of positively charged PS-NH 2. In addition, they can prevent the uptake of both PS-NH 2 and PS-COOH through reducing the porosity on the surface of the cell walls. These finally alleviated the toxicity of oxidative stress caused by PS-NPs and improved the viability of rice cells. Our findings demonstrated the significant contribution of Si in combating PS-NPs in rice. [Display omitted] • PS-NH 2 were accumulated at relatively low levels in cells compared with PS-COOH. • Silicon (Si) can inhibit the uptake of PS-NPs in cells by electrostatic adsorption. • Si can inhibit the uptake of PS-NPs in cells by changing the porosity of the cell walls. • Si alleviated the toxicity of ROS that caused by PS-NPs. • Si improved the viability of cell under PS-NPs stress. [ABSTRACT FROM AUTHOR]

Recognition and deconstruction of biomass recalcitrance are essential steps in fuel ethanol production. Aqueous ammonia (AA) is an efficient pretreatment to improve the enzymatic digestibility of sugar beet pulp (SBP), but the precise mechanism is still ambiguous. Multidimensional methods, e.g., physical properties, wet chemistry compositions, and glycome profiling were integrated to elucidate the impacts of AA pretreatment on recalcitrance of SBP semi-quantitatively. Additionally, the variations in enzyme adsorption and cell wall morphology during the enzymatic hydrolysis were systematically observed. The results confirmed that the constitution, association, and distribution of glycan epitopes within cell walls significantly correlated to recalcitrance. Specifically, the arabinogalactan and rhamnogalacturonan epitopes negatively correlated to the recalcitrance. And xylans only bound to cellulose contributed to recalcitrance. Dislocation and fragmentation of cell walls through sequential removal of several glycan epitopes could facilitate enzymatic digestibility, in terms of enzyme adsorption, reducing sugar yields, and enzymatic saccharification behaviors. Whereas, cell corners seemed to be highly resistant to enzymatic digestion due to some gathered epitopes. The maximum reducing sugar yields ranging from 437.7 to 441.48 mg/g were obtained from the pretreated SBP (3, 5, and 7 h), which nearly increased by 87% compared to the control. Selecting a proper pretreatment to precisely strip out the vital glycan epitopes might be an economically feasible strategy in fuel ethanol production. [Display omitted] • Aqueous ammonia leaded to heterogeneous constitution and distribution of glycans. • Heterogeneous evolution of glycan epitopes caused contrasted degradation profiles. • Concomitant gather of glycan epitopes strengthened recalcitrance of cell corners. • Enzymatic degradation patterns of cell walls were used to reflect recalcitrance. [ABSTRACT FROM AUTHOR]

Highland barley (HB), oats, and unpolished rice (UR) are known to inhibit starch digestion. β-Glucan and structural barriers are the main factors contributing to low digestibility; however, the hypoglycaemic mechanism of these grains is still unclear. Here, food systems in the forms of flour and chymes were constructed to understand their roles. There was little difference in starch digestibility for the flours of the various grains. We speculated that β-glucan in flours could not delay digestion, and the low viscosity of gelatinised HB flour supported this hypothesis. The digestibility of chymes was lower than flours, especially for HB chyme. After cooking, more bran structures and granular starch were still observed in the HB kernels. The digested grain structure showed that the starch hydrolysis level of UR and oats was higher than that of HB. Also, the starches in the bran encapsulated exhibited a good ability of anti-hydrolysis than those in the exposed endosperm. These results all indicate that intact physical structures effectively hindered gelatinisation and digestion. This study demonstrates that structural barriers exert a more important effect on starch bioaccessibility than β-glucan, which can provide useful guidance for glycaemia management. [Display omitted] • Highland barley flour had a high starch digestibility even with more β-glucan. • Bran and cell walls hinder starch gelatinisation and hydrolysis. • Structural barriers of highland barley effectively inhibit starch digestion. [ABSTRACT FROM AUTHOR]

Water uptake by mature barley grains initiates germination and is the first stage in the malting process. Here we have investigated the effects of starchy endosperm cell wall thickness on water uptake, together with the effects of varying amounts of the wall polysaccharide, (1,3;1,4)-β-glucan. In the latter case, we examined mutant barley lines from a mutant library and transgenic barley lines in which the (1,3;1,4)-β-glucan synthase gene, HvCslF6 , was down-regulated by RNA interference. Neither cell wall thickness nor the levels of grain (1,3;1,4)-β-glucan were significantly correlated with water uptake but are likely to influence modification during malting. However, when a barley mapping population was phenotyped for rate of water uptake into grain, quantitative trait locus (QTL) analysis identified specific regions of chromosomes 4H, 5H and 7H that accounted for approximately 17%, 18% and 11%, respectively, of the phenotypic variation. These data indicate that variation in water uptake rates by elite malting cultivars of barley is genetically controlled and a number of candidate genes that might control the trait were identified under the QTL. The genomics data raise the possibility that the genetic variation in water uptake rates might be exploited by breeders for the benefit of the malting and brewing industries. [ABSTRACT FROM AUTHOR]

Resistant bacterial infections are a major health problem in many parts of the world. The major commercial antibiotic classes often fail to combat common bacteria. Although antimicrobial peptides are able to control bacterial infections by interfering with microbial metabolism and physiological processes in several ways, a large number of cases of resistance to antibiotic peptide classes have also been reported. To gain a better understanding of the resistance process various technologies have been applied. Here we discuss multiple strategies by which bacteria could develop enhanced antimicrobial peptide resistance, focusing on sub-cellular regions from the surface to deep inside, evaluating bacterial membranes, cell walls and cytoplasmic metabolism. Moreover, some high-throughput methods for antimicrobial resistance detection and discrimination are also examined. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides. [ABSTRACT FROM AUTHOR]

Acrylamide (AA) is formed by Maillard Reaction (MR), during high-temperature and low moisture processes in several food categories, including bakery products. AA is classified as a toxic and carcinogenic compound and therefore, mitigation strategies are necessary to control its concentration in foods. Selecting ingredients with a reduced amount of asparagine, the main AA precursor, is the most effective method of reducing the AA formation in bakery products. In the present study, the hypothesis that cotyledon cell walls integrity could prevent the formation of AA by modulating the dehydration rate and reducing the availability of asparagine during the MR development during baking was investigated. Legumes have strong cotyledon cell walls that can be preserved during flour production: in this study two kidney bean flours with intact and broken cell walls were used. The integrity of the cotyledon cell walls was assessed by scanning electron microscopy while AA, its precursors, moisture and water activity were measured in bean flours, raw doughs and baked biscuits. The biscuits were also characterised for the main baking parameters such as weight loss, pH, colour and texture. The results showed that biscuits formulated with bean flour with intact cell walls had a 15% less amount of AA than those made with the bean with damaged cell walls at the end of the cooking time. Furthermore, the use of the two different bean flours led to different quality characteristics of the biscuits in terms of hue angle and browning index, as colour parameters, and hardness, which is related to the texture properties. These differences were attributed to the different development of the MR and in the structure of the biscuit during baking. The use of intact plant tissue legume flours in alterative biscuits formulations is a feasible and low-cost approach that can contribute to the AA mitigation strategy. • The different preparations of the bean flours led to different cell walls integrity. • Biscuits made with intact bean flours developed the lowest level of acrylamide. • Asparagine was less available for the acrylamide formation in intact bean flour. • Biscuits made with damaged bean flours developed the highest level of acrylamide. • Biscuits made with damaged bean flour dehydrated more quickly during baking. [ABSTRACT FROM AUTHOR]

Boron (B) is an essential element for plant growth but its cellular functions are poorly defined. We conducted transcriptome analysis of shoot apices of pea (Pisum sativum L.) growing for up to 18 days in the presence or absence of borate. Shoots of B deficient plants exhibited impaired elongation of the apex but increased growth of lateral shoots. Transcriptome analysis at days 10, 14 and 18 revealed 42, 517 and 2684 differentially expressed genes (DEGs), respectively, relating to diverse aspects of cell growth, metabolism, membrane function and cell signaling. Genes involved in jasmonate signaling and cell wall metabolism were upregulated in the B deficient plants. Many DEGs encoded transcription factors (TFs) potentially involved in these responses including many MYB and ethylene-responsive transcription factor (ERF) proteins and two orthologs of MYC2 which has been implicated in jasmonate signaling. Treatment of detached apices with B or jasmonic acid (JA) led to rapid changes in the expression of several of these DEGs. These results are consistent with a major role for borate in cell wall structure, perturbation of which can activate jasmonate signaling and cell wall remodeling. Such changes can help to explain how B deficiency leads to changes in shoot growth and architecture. • Boron deficiency leads to impaired growth of the shoot apex in pea plants. • Boron deficiency activates jasmonate signaling. • Boron deficiency causes widescale changes in expression of genes for cell wall components and metabolism. [ABSTRACT FROM AUTHOR]

The anatomical and histochemical study of young and adult endocarps of Argania spinosa (sampled from Tindouf; Algeria) shows a general structure that is similar to that of majority of stone fruits. These samples consist of tissues that contain lignified and cellulosic cell walls. The majority of the tissues are composed of sclerenchyma cells; with very thick lignified cell walls and conducting tissues. Coniferyl lignins are abundant in the majority of the lignified tissues. However, the coniferyl lignins appear at the primary xylem during lignification. Syringyl lignins are present in small quantities. The electron microscopy observation of the sclerenchyma cell walls of the young endocarp shows polylamellate strates and, cellular microfibrils in arced patterns. This architecture is observed in the cell walls of the adult endocarp only after the incubation of the tissue in methylamine. These configurations (arcs) are the result of a regular and complete rotation with a 180° variation in the microfibril angle; the complete and symmetrical arcs show a helicoidal mode of construction. The observation of the sclerenchyma cells revealed the capacity of helicoidal morphogenesis to adjust itself under the influence of topological constraints, such as the presence of a large number of pit canals, which maintain symplastic transport. [ABSTRACT FROM AUTHOR]

[Display omitted] • Grape polysaccharides were extracted from different sources: pomace, must, wine, lees. • Grape polysaccharide composition depends on the matrix used for the extraction. • Grape by-products can emerge as a potential source of polysaccharides. • White pomace is a good source to obtain valuable grape by-products rich in polysaccharides. One of the most important challenges of the oenological industry is the recovery and valorization of valuable compounds from grapes and grape by-products. Recent studies have focused on the obtention of phenolic compounds, but little attention has been paid to the extraction of grape polysaccharides, which could have a great potential as oenological products but also for their benefits to human health. This study aimed to recover polysaccharides from different grape and winemaking products and provide information about its composition. The results obtained with the white pomace and white lees revealed its potential to be exploited to obtain extracts rich in polysaccharides. White pomace revealed as a good source to obtain polysaccharides rich in arabinose and galactose (PRAG) and glucosyl polysaccharides. White lees showed a potential to be used to recover mannoproteins and glucans. Both extracts showed high polysaccharide purity (55.5% and 51.9%, respectively). Extracts rich in rhamnogalacturonan type II (RG-II) were obtained from a red wine (89.7% polysaccharide purity) and from the wash water used by the distillery after draining the distilled wine pomace (40.6% polysaccharide purity). Our results open new lines to obtain extracts with different polysaccharide composition, non-available in the market. Future studies are needed to evaluate their potential as stabilizing or finning agents and possible alternative solutions to traditional animal-origin protein fining agents. [ABSTRACT FROM AUTHOR]

Abstract: Expansin proteins extend plant cell walls by a hydrolysis-free process that disrupts hydrogen bonding between cell wall polysaccharides. However, it is unknown if this mechanism is operative in mushrooms. Herein we report that the native wall extension activity was located exclusively in the 10 mm apical region of 30 mm Flammulina velutipes stipes. The elongation growth was restricted also to the 9 mm apical region of the stipes where the elongation growth of the 1st millimetre was 40-fold greater than that of the 5th millimetre. Therefore, the wall extension activity represents elongation growth of the stipe. The low concentration of expansin-like protein in F. velutipes stipes prevented its isolation. However, we purified an expansin-like protein from snail stomach juice which reconstituted heat-inactivated stipe wall extension without hydrolytic activity. So the previous hypotheses that stipe wall extension was resulted from hydrolysis of wall polymers by enzymes or disruption of hydrogen bonding of wall polymers exclusively by turgor pressure are challenged. We suggest that stipe wall extension may be mediated by endogenous expansin-like proteins that facilitate cell wall polymer slippage by disrupting noncovalent bonding between glucan chains or chitin chains. [Copyright &y& Elsevier]

Highlights: [•] Hydration properties of AX films are affected by arabinose substitution. [•] Mechanical properties of AX films are affected by arabinose substitution. [•] BG films exhibit higher extensibility than AX films. [•] The extensibility of BG layer may favor cell wall extension during grain development. [•] The diversity of AX possibly modulates the hydration properties of cell walls. [ABSTRACT FROM AUTHOR]

Abstract: Municipal solid waste (MSW) contains significant quantities of plant-derived carbohydrates which have the potential to be exploited as a biomass source. This study evaluated the chemical composition and fractionation of MSW water-insoluble organic matter remaining after recycling of other components (MSWR). The organic matter was prepared as a dry, alcohol insoluble residue (MSWR-AIR, comprising w = 6% of original MSW) and size fractionated into fractions A, B, C & D. Carbohydrates were present in all the sub-fractions, comprising up to w = 54%; their complexity was also assessed by FT-IR spectroscopy. The lignin content in the samples ranged from w = 11–22%. The most carbohydrate-rich subfraction (C; w = 4% original MSW) was sequentially extracted to provide information on the likely constituent cell wall-derived polymers, sugar compositions and uronic acid content. The results indicate that approximately w = 25% of the MSWR-AIR comprises glucose, which appears to be mostly cellulosic in origin. The results are discussed in relation to the potential for exploitation. [Copyright &y& Elsevier]

Abstract: Several studies have demonstrated a range of effects of outdoor UV-B supplementation during the growing season on leaf chemistry including carbohydrate extractability and on the subsequent decomposition of leaf litter. However, this study investigates the effects of several levels of UV radiation on leaf carbohydrate chemistry and subsequent decomposition using filtration of ambient sunlight. Fraxinus excelsior seedlings were grown outdoors in the UK under ambient solar irradiation and under filtration treatments which excluded either UV-B or both UV-A and UV-B. After one year of decomposition in the litter layer of a mixed semi-natural woodland, the loss of dry mass was 10% greater, relative to starting mass, in the leaves which had received no UV at all or no UV-B throughout the growing season (P <0.05). Analysis of the cell wall material before decomposition revealed no significant trends in total carbohydrate and lignin content with UV exclusions, no change in foliar nitrogen and C-to-N ratio and a 2% increase in foliar carbon (P <0.05) only with the combined exclusion of UV-A and UV-B. A sequential extraction of carbohydrate with a series of extractants (phosphate buffer, ammonium oxalate, urea, sodium hydroxide and formic acid) showed no trends with UV exclusions but digestion with the fungal enzyme mixture Driselase revealed that exclusion of UV-B only caused rhamnose and mannose residues of the cell-wall polysaccharides to resist Driselase digestion whist exclusion of all UV had the opposite effect. Whereas some studies have reported that elevated UV-B radiation from lamp supplementation can increase rates of subsequent leaf decomposition, the higher UV-B levels in the ambient controls of this filtration study resulted in 29% lower decomposition rates than the filtered-UV treatments. [Copyright &y& Elsevier]

Abstract: The effect of a macerating enzyme and maceration time on the structure of grape skin cell walls and on wine quality was studied by making wines with different maceration times with and without the addition of enzyme. The results show that the addition of a macerating enzyme accelerates the extraction of phenolic compounds, reducing the maceration time needed for high quality winemaking. The degradation of grape skin cell walls was influenced by the enzyme, which mainly affected the pectin fraction of the cell wall. [Copyright &y& Elsevier]

Abstract: Cell wall appositions (CWAs), formed by the deposition of extra wall material at the contact site with microbial organisms, are an integral part of the response of plants to microbial challenge. Detailed histological studies of CWAs in fern roots do not exist. Using light and electron microscopy we examined the (ultra)structure of CWAs in the outer layers of roots of Asplenium species. All cell walls studded with CWAs were impregnated with yellow-brown pigments. CWAs had different shapes, ranging from warts to elongated branched structures, as observed with scanning and transmission electron microscopy. Ultrastructural study further showed that infecting fungi grow intramurally and that they are immobilized by CWAs when attempting to penetrate intracellularly. Immunolabelling experiments using monoclonal antibodies indicated pectic homogalacturonan, xyloglucan, mannan and cellulose in the CWAs, but tests for lignins and callose were negative. We conclude that these appositions are defense-related structures made of a non-lignified polysaccharide matrix on which phenolic compounds are deposited in order to create a barrier protecting the root against infections. [Copyright &y& Elsevier]

Abstract: The cell wall-cosolvent partition coefficients (K m ) of polycyclic aromatic hydrocarbons (PAHs) were determined for Rhizopus oryzae cell walls by controlling the volume fraction of methanol (f) ranging from 0.1 to 0.5. Five cosolvent models were employed for extrapolating the cell wall-water partition coefficients (K w ) in pure water. The extrapolated K w values of four PAHs on R. oryzae cell walls were ranged from 2.9 to 5.1. Comparison of various K w values of pyrene generated from extrapolation and the QSPR model, together with predicted different (PD), mean percentage deviations (MPD), and root mean square errors (RSE), revealed that the performance of the LL and Bayesian models were the best among all five tested cosolvent models. This study suggests that R. oryzae cell walls play an important role in the partitioning of PAHs during bioremediation because of the high K w of fungal cell walls. [Copyright &y& Elsevier]

Abstract: Arabinoxylans may account for up to 25% of the mass of grass cell walls. The interactions of these polysaccharides with themselves and with cellulose and lignin is believed to affect the walls physical properties and increase the walls resistance to biochemical conversion to fermentable sugars. Arabinoxylans have a backbone composed of 1,4-linked β-d-xylosyl residues, some of which are substituted at O-2 or O-3 with single arabinofuranosyl (Araf) residues. The Araf residues are likely transferred from UDP-Araf to the xylan backbone by arabinofuranosyltransferases. UDP-Araf is itself formed from UDP-arabinopyranose (UDP-Arap) by UDP-arabinopyranose mutase (UAM). In this study, RNA interference (RNAi) was used to suppress UAM expression in rice plants and thereby reduce the amounts of UDP-Araf available for cell wall synthesis. Several of the transgenic plants had reduced proportions of Araf in their walls together with a decrease in the extent of substitution of the xylan backbone, and a reduction of between 25% and 80% in ferulic acid and p-coumaric acid contents of the cell walls. Those transgenic plants with >25% reduction in the amounts of Araf were dwarfed and infertile. [Copyright &y& Elsevier]

Abstract: Initial crushing and pressing operations have a major influence on the polyphenolic composition of apple juice, therefore, we have tested the impact of variations of this step using three cider apple cultivars of contrasting polyphenolic composition: Guillevic, Kermerrien and Dous Moen. Under inert atmosphere, increased temperature (between 5°C and 24°C), increased the extraction of procyanidins from fruit to juice. The crushed apples were also subjected to four conditions of oxidation: preserved from oxidation as above, short contact with air, short contact with air and mixing, long contact with air and mixing. Oxidation decreased the concentrations of native polyphenols in the juices, especially for flavan-3-ols. The golden colour of the juices was initially enhanced with increases in saturation C∗ and a shift of the hue angle from yellow to orange. However, for the highest oxidation state the colour became paler and more yellow. Bitterness and astringency decreased upon oxidation, probably due to increased retention of oxidised moieties. [ABSTRACT FROM AUTHOR]

Abstract: The effects of chilling on cell wall metabolism of tomato fruit (Solanum lycopersicum L. cv. Trust) have been investigated. Fruit were harvested at the breaker stage of maturity and ripened at 20°C for 1–12d, or stored at 3°C for up to 3 weeks, and then ripened at 20°C. The effects of cold storage on fruit ripening were small. Pericarp tissues from fruit stored for 2 weeks had only slightly reduced pectin solubilization and depolymerization. Polygalacturonase (PG) mRNA levels, PG protein accumulation and PG activity in the tissues were also reduced by chilling. A reduction of PG protein abundance and PG activity occurred to a greater extent than that of PG mRNA levels, suggesting that chilling affected post-transcriptional regulation. Expression of the expansin1 (LeEXP1) gene was also reduced by chilling, but LeExp1 protein accumulation levels were not affected by chilling. β-Galactosidase activity was highest in chilled fruit during cold storage and during early ripening, but expression of a β-galactosidase gene (TBG4) was unaffected. While chilling had no effect on pectin methylesterase (PME) activity, expression of PME1 in tissues from cold-stored fruit was lower. Endo-β-1,4-glucanase (EGase) activity and the expression of endo-β-1,4-glucanase (Cel1) were not affected by chilling. The predominant effect of chilling on the activity, protein accumulation, and gene expression of PG did not correlate with pectin solubilization and depolymerization. [Copyright &y& Elsevier]

Abstract: The genome of Brachypodium distachyon, also known as purple false brome, was fully sequenced in 2008 largely in response to the demand for a model plant for temperate grasses. A comparative study of the primary cell walls of seedlings of B. distachyon, Hordeum vulgare and Triticum aestivum was carried out. The cell walls of the three species were characterized by similar relative levels of, and developmental changes in, hemicelluloses. The occurrence of (1,3;1,4)-β-d-glucans was correlated with phases of growth involving cell elongation. Expression profiling of the genes involved in (1,3;1,4)-β-d-glucan synthesis (cellulose synthase-like F family (CSLF), CSLH and a putative synthase gene CSLJ) did not show a transcriptional regulation that corresponded to the abundance of (1,3;1,4)-β-d-glucans. CSLF6 transcripts were similarly highly expressed in all three grasses, and were much more abundant than any of the other transcripts. The CSLH transcript was relatively abundant in B. distachyon but almost undetectable in the other species. The deposition of arabinoxylans increased steadily during seedling growth in all three grasses, but they became less substituted and more cross-linked into the wall matrix during cell maturation. Moreover, arabinoxylans in B. distachyon differed from the two other grasses in having a lower degree of arabinose substitution, a higher percentage of ferulic acid in form of dimers and a larger proportion of ester-linked p-coumaric acid. [Copyright &y& Elsevier]

Summary: Endo-β-mannanase is thought to play a role in tomato fruit ripening by participating in the degradation of cell walls. Its spatial and temporal expression during ripening was examined, as was the relationship between its activity and softening of the fruit using a large number of tomato lines, and by suppression of transcription of the endo-β-mannanase (LeMan4a) gene. Immunolocalization studies showed that the enzyme is expressed in the fruit cell wall at all ripening stages, but it is not active during the initial green stage; this is not due to the presence of inhibitors of its activity, nor due to changes in its mRNA sequence. Transient expression in onion epidermal cells of endo-β-mannanase transcripts fused to green fluorescent protein resulted in the expressed enzyme being localized to the cell walls. Transgenic tomato plants expressing a GUS gene attached to the LeMan4a promoter showed that this occurs initially during ripening in the skin and outer pericarp of the fruit, and later in the skin and throughout the pericarp. Fruit firmness and activity of endo-β-mannanase were not strongly correlated during ripening of many lines of tomato. Several plants of cv. Micro-Tom were transformed using RNA interference (mRNAi) and antisense RNA strategies to suppress transcription of the LeMan4a gene. When endo-β-mannanase activity was much reduced in the transgenic fruits, their firmness was higher compared to those of control fruits at the turning and orange-color stages, but at the red-ripe stage firmness was similar between the two fruit types. We suggest that while the enzyme does participate in fruit ripening it alone is not sufficient to cause hydrolysis of the cell walls which results in their weakening; it likely plays a cooperative role with other known wall-modifying enzymes, and/or is involved in cell wall rearrangement. [Copyright &y& Elsevier]

In this study, wood-epoxy polymer composites (WEPC) with excellent mechanical properties were prepared by adjusting the stress–strain system under mechanical load after introducing epoxy monomers into the cell cavities of plantation wood. The flexural strength, modulus, compression strength, and impact strength of the WEPCs were improved by up to 110.3%, 86.5%, 137.3%, and 110.6%, respectively. The flexure strength (140.5 MPa) was far beyond strength class TB20 (98 MPa), which was higher than that of rosewood. The improvement in mechanical strength was mainly attributed to the change of stress concentration properties by sharing the load with the epoxy polymer and the enhanced cell walls. The enhanced toughness was attributed to the increase in longitudinal cell splitting, as well as the "propagation of cracks" and "debonding" among multilevel structures of cell walls. The mechanical failure mechanism of WEPCs can be used as a reference for the design of wood-based composites. • High performance composites were prepared by introducing epoxy polymers in wood. • The mechanical properties of the wood-based composites could be controlled. • Mechanical failure behavior of the composites changed compared to untreated wood. [ABSTRACT FROM AUTHOR]

The aim of this study was to clarify the importance of the soluble fraction on cell wall decomposition. Wheat plant was chosen as a model and was harvested at three stages of maturity: anthesis (A stage), 20 days after anthesis (B stage) and physiological maturity (PM stage). Wheat third internode (numbered down from the ear) were selected for this study. Internode age influenced the cumulative CO2 kinetics with internodes from wheat stem harvested at anthesis mineralizing 62.1%±2.2 of added residue C whereas those harvested at the B and PM stages mineralized 58.8%±1.4 and 51.6%±1.7, respectively of the added C. Chemical analyses revealed that maturation of the selected internodes mainly altered residue quality by modifying the proportion of soluble to cell wall fractions rather than the quality of these fractions. The hexose to pentose ratios were good biomarkers of microbial sugars for both soluble and cell wall fractions, as were the uronic acids, which are not commonly determined in soil decomposition studies. This study clearly demonstrated that the contents of the internode soluble fraction did not affect the extent of cell wall C mineralization. Therefore, the soluble content of crop residues would not regulate the soil microbial populations able to mineralize cell wall C. However, this needs to be validated on a broader range of residue types with different nature of cell wall C or soluble compounds. [Copyright &y& Elsevier]

Abstract: This study was completed to investigate whether a fibrolytic enzyme preparation with xylanase and cellulase activities (Fibrozyme™, Alltech Inc., Nicholasville, KY, USA), could stimulate in vitro rumen fermentation of alfalfa hay, grass hay and barley straw, and their isolated cell walls as neutral detergent fibre (NDF). Samples (500mg) of each substrate were incubated in 120ml bottles with 50ml of buffered rumen fluid from sheep at 39°C. The enzyme preparation was added directly to the bottles at the beginning of the incubation at levels of: 0 (control; CON), 50mg/g substrate DM (LOWFIB) and 100mg/g substrate DM (HIGHFIB). Effects on volatile fatty acid (VFA) production depended on substrate and incubation time. After incubation for 5h, enzyme addition increased (P<0.05) production of VFA and acetate compared to CON for both alfalfa hay and its isolated cell wall, and increased (P<0.05) propionate and butyrate production in isolated cell wall, but reduced (P<0.05) them in alfalfa hay. After incubation for 10h, addition of both doses of enzyme preparation increased (P<0.05) VFA and propionate production versus CON for both alfalfa hay and its isolated cell wall, and decreased (P<0.05) acetate to propionate ratios with both substrates, with intermediate values for LOWFIB and highest for HIGHFIB. After 24h of incubation, there were no effects due to enzyme treatment or enzyme dose on rumen variables. Addition of both doses of supplemental enzyme increased (P<0.05) VFA, acetate and propionate production after 5 and 10h incubation in both grass hay and its isolated cell wall, with increases being greater (P<0.05) for HIGHFIB versus LOWFIB in all variables. Both doses of enzyme addition reduced (P<0.05) the acetate to propionate ratio at 5 and 10h of incubation. After 24h of incubation, enzyme addition increased (P<0.05) VFA, acetate and butyrate production in both grass hay and its isolated cell wall versus CON, with some dose effects on both substrates. Enzyme supplementation also increased (P<0.05) VFA, acetate and propionate production versus CON in barley straw and its isolated cell wall at 5 and 10h of incubation, with dose dependent effects after incubation for 5h with higher (P<0.05) increases for HIGHFIB versus LOWFIB in both substrates. Both enzyme doses also reduced (P<0.05) the acetate to propionate ratio in both barley straw and its cell wall after incubation for 5h. Production of total VFA and butyrate increased (P<0.05) with both doses of enzyme after incubation for 24h. Final pH, ammonia-N and disappearance of aNDF and ADF did not differ among enzyme treatments after incubation of grass hay and barley straw or their isolated cell wall for 24h. Results indicate that this fibrolytic enzyme preparation stimulated in vitro fermentation of substrates at short (5 and 10h), but not at long (24h) incubation times, and that effects depended on both the dose used and the presence of neutral detergent soluble components in the substrate. [Copyright &y& Elsevier]

Abstract: Cell walls of roots have a great reactivity towards metals, and may act as a barrier limiting the entry of metals, especially in non-hyperaccumulating species. The aim of this study was to determine the localization and speciation of Zn in roots of tobacco (Nicotiana tabacum) grown in Zn-contaminated substrates. Chemical extractions and EXAFS spectroscopy were applied on whole roots and on isolated cell walls of roots. Our results show that cell walls of roots exhibited a distribution of Zn affinity sites, from water-soluble to non-exchangeable Zn. In whole roots, Zn was bound with oxalate and other COOH/OH groups: the first species was probably intracellular while the second was attributed to Zn bound to the cell walls and, to a lesser extent, to intracellular organic acids. Moreover, Zn-phosphate was also identified, and this species was CuSO4-extractable. It probably resulted from chemical precipitation in the apoplasm, and explained the steady increase in exchangeable root Zn observed in root of tobacco during the culture. This study shows the strength of combining EXAFS and chemical extractions for studying localization and speciation of metals in plants. [Copyright &y& Elsevier]

Abstract: This review describes the biochemical bases for color and firmness changes in fruit and vegetable tissues, since appearance and texture are two of the most fundamental factors affecting the quality of fresh-cut products. The intent is to provide a level of understanding that can be used to underpin future research directions in order to resolve existing issues that limit fresh-cut quality and shelf life. The biochemical mechanisms for enzymatic browning mediated by polyphenol oxidase and phenol peroxidase are described, and the importance of limiting cellular damage during the processing of fresh-cut fruit and vegetable products is emphasized. Also described are two mechanisms of chlorophyll degradation involved in discoloration events in green tissues, and examples of coloring processes specific to particular crops (white blush in carrots, discoloration of Allium spp., secondary browning in apples). The loss of desirable texture in fresh-cut products is a major problem. In fruit this is largely due to a continuation of cell wall disassembly events that are a normal component of ripening, and which result in declining cell wall strength and reduced intercellular adhesion. In some species the process is exacerbated by wound-response ethylene. However, wounding, water loss and ripening-related turgor changes are also important contributors to textural deterioration. In fresh-cut vegetables, water loss and damage-induced lignification are common problems. The effects of factors such as maturity at harvest, processing conditions and various treatments to mitigate quality decline are discussed. [Copyright &y& Elsevier]

Abstract: Changes in homogalacturonans (HGs) and enzymes degrading them have been investigated during cotton (Gossypium hirsutum L.) cotyledon expansion. Using an in vivo assay for pectin-degrading enzymes that involves fluorescent labeled oligomers of GalA as substrate and capillary electrophoresis for product analysis, we found that endo- and exo-polygalacturonases are present in the cotyledon extracellular spaces, and there are dramatic changes in the levels of both activities as the cotyledons change their rate of expansion. Capacity for endo-polygalacturonase activity was highest during the initial stages of cotyledon expansion. However, for exo-polygalacturonase activity it was highest in the later stages of expansion. Cell walls were prepared from 3-, 5-, and 7-day-old cotton cotyledons and treated with liquid HF at −23°C. This treatment cleaves the glycosidic linkages of most neutral sugars in the walls without degrading HGs. HGs with a relatively high degree of esterification can then be solubilized with water, and those with low esterification can be solubilized with concentrated imidazole buffer. The majority of HGs were obtained in the water extracts. The degrees of esterification were 57%, 47%, and 47% in water extracts and 34%, 25%, and 27% in imidazole extracts, in 3-, 5-, and 7-day-old cotton cotyledons, respectively. Using a PA100 ion-exchange column, the members of a GalA homologous series up to approximately 70 residues can be separated. The results from HG molecular length distribution analysis indicated that the HG at 3 days was on average shorter than that in the older cotyledons, perhaps reflecting the higher level of endo-polygalacturonase activity at this stage of more rapid growth. [Copyright &y& Elsevier]