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This study investigated the chemical composition (proximate and Van Soest analysis) and in vitro gas production parameters of maize leaves and stems separately, and related the in vitro gas production parameters with the chemical composition, of thirteen maize cultivars. After harvest in September 2016, all plants were separated into two morphological fractions: leaves and stems. The crude protein (CP) content was greater, and the ratio of acid detergent lignin (ADL) to potentially rumen degradable fibre (calculated as the difference between neutral detergent fibre and ADL; ADL:pRDF) was lower in the leaves than in the stems in all 13 cultivars. For the leaves, the cumulative gas production between 3 and 20 hr (A2), representing cell wall fermentation in the rumen fluid, and the cumulative 72‐hr gas production (GP72), representing total organic matter (OM) degradation, were moderately to weakly correlated with the chemical composition, including hemicellulose, cellulose, ADL and CP content (R 2

This review presents information on the relationship of ultrastructure and composition of wood cell walls, in order to understand how wood degrading bacteria utilise cell wall components for their nutrition. A brief outline of the structure and composition of plant cell walls and the degradation patterns associated with bacterial degradation of wood cell walls precedes the description of the relationship of cell wall micro- and ultrastructure to bacterial degradation of the cell wall. The main topics covered are cell wall structure and composition, patterns of cell wall degradation by erosion and tunnelling bacteria, and the relationship of cell wall ultrastructure and composition to wood degradation by erosion and tunnelling bacteria. Finally, pertinent information from select recent studies employing molecular approaches to identify bacteria which can degrade lignin and other wood cell wall components is presented, and prospects for future investigations on wood degrading bacteria are explored.

Background Lentinula edodes is one of the most popular edible mushroom species in the world and contains useful medicinal components, such as lentinan. The light-induced formation of brown film on the vegetative mycelial tissues of L. edodes is an important process for ensuring the quantity and quality of this edible mushroom. To understand the molecular mechanisms underlying this critical developmental process in L. edodes, we characterized the morphological phenotypic changes in a strain, Chamaram, associated with abnormal brown film formation and compared its genome-wide transcriptional features. Results In the present study, we performed genome-wide transcriptome analyses of different vegetative mycelium growth phenotypes, namely, early white, normal brown, and defective dark yellow partial brown films phenotypes which were exposed to different light conditions. The analysis revealed the identification of clusters of genes specific to the light-induced brown film phenotypes. These genes were significantly associated with light sensing via photoreceptors such as FMN- and FAD-bindings, signal transduction by kinases and GPCRs, melanogenesis via activation of tyrosinases, and cell wall degradation by glucanases, chitinases, and laccases, which suggests these processes are involved in the formation of mycelial browning in L. edodes. Interestingly, hydrophobin genes such as SC1 and SC3 exhibited divergent expression levels in the normal and abnormal brown mycelial films, indicating the ability of these genes to act in fruiting body initiation and formation of dikaryotic mycelia. Furthermore, we identified the up-regulation of glycoside hydrolase domain-containing genes in the normal brown film but not in the abnormal film phenotype, suggesting that cell wall degradation in the normal brown film phenotype is crucial in the developmental processes related to the initiation and formation of fruiting bodies. Conclusions This study systematically analysed the expression patterns of light-induced browning-related genes in L. edodes. Our findings provide information for further investigations of browning formation mechanisms in L. edodes and a foundation for future L. edodes breeding. Electronic supplementary material The online version of this article (10.1186/s12864-019-5509-4) contains supplementary material, which is available to authorized users.

Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc) lead to the devastating rice bacterial diseases and have a very close genetic relationship. There are tissue-specificity differences between Xoo and Xoc, i.e., Xoo only proliferating in xylem vessels and Xoc spreading in intercellular space of mesophyll cell. But there is little known about the determinants of tissue-specificity between Xoo and Xoc. Here we show that Xoc can spread in the intercellular spaces of mesophyll cells to form streak lesions. But Xoo is restricted to growth in the intercellular spaces of mesophyll cells on the inoculation sites. In vivo, Xoc largely breaks the surface and inner structures of cell wall in mesophyll cells in comparison with Xoo. In vitro, Xoc strongly damages the cellulose filter paper in comparison with Xoo. These results suggest that the stronger cell wall-degradation ability of Xoc than that of Xoo may be directly determining the tissue-specificity.

BACKGROUND The relationship between the chemical and molecular properties – in particular the (acid detergent) lignin (ADL) content and composition expressed as the ratio between syringyl and guaiacyl compounds (S:G ratio) – of maize stems and in vitro gas production was studied in order to determine which is more important in the degradability of maize stem cell walls in the rumen of ruminants. Different internodes from two contrasting maize cultivars (Ambrosini and Aastar) were harvested during the growing season. RESULTS The ADL content decreased with greater internode number within the stem, whereas the ADL content fluctuated during the season for both cultivars. The S:G ratio was lower in younger tissue (greater internode number or earlier harvest date) in both cultivars. For the gas produced between 3 and 20 h, representing the fermentation of cell walls in rumen fluid, a stronger correlation (R2 = 0.80) was found with the S:G ratio than with the ADL content (R2 = 0.68). The relationship between ADL content or S:G ratio and 72‐h gas production, representing total organic matter degradation, was weaker than that with gas produced between 3 and 20 h. CONCLUSION The S:G ratio plays a more dominant role than ADL content in maize stem cell wall degradation. © 2017 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The heartwoods of many wood species have natural resistance to wood decay due to the accumulation of antifungal heartwood extractives. The natural durability of heartwoods has been extensively investigated, yet very little information is available on the initiation of heartwood decay. This experiment examined the onset of Rhodonia placenta brown rot decay in Scots pine heartwood in order to identify the key changes leading to heartwood decay. An imaging approach based on Raman imaging and multivariate image analysis revealed that the degradation of heartwood began in the innermost cell wall layers and then spread into the remaining cell walls and the middle lamella. Pinosylvins were extensively degraded in the cell walls, middle lamella and extractive deposits, while unidentified material most likely consisting of hemicelluloses and/or lipophilic extractives was removed from the inner cell wall layers. Changes similar to inner cell wall degradation were seen in the remaining cell walls in more advanced decay. The results indicate that the key change in incipient heartwood decay is the degradation of antifungal heartwood extractives. The inner cell wall degradation seen in this experiment may serve a nutritive purpose or facilitate the penetration of degradative agents into the cell walls and middle lamella.

Different winemaking practices are aimed at increasing cell wall degradation to facilitate extraction of valuables molecules into the wine. However, little attention has been paid to the composition of marcs from different cultivars according to the influence of the winemaking procedures. We provide information on skin cell walls from Cabernet Sauvignon, Syrah and Monastrell grapes and examine how different winemaking practices (addition of enzymatic preparation and β-galactosidase separately and dry ice addition) may affect the composition of marc skin cell wall material (CWM). The efficiency of CWM isolation from the grape skin and also its composition is influenced by the cultivar. A similar cultivar influence has been detected on CWM from the marc, being the differences also due to the enological technique. Our results help to increase our knowledge on the degradation of cell walls during vinification, while providing a valuable guideline to upgrade the value of these by-products.

Ricinosomes are specialized ER-derived organelles that store the inactive pro-forms of KDEL-tailed cysteine endopeptidases (KDEL-CysEP) associated with programmed cell death (PCD). The Arabidopsis genome encodes three KDEL-CysEP (AtCEP1, AtCEP2, and AtCEP3) that are differentially expressed in vegetative and generative tissues undergoing PCD. These Arabidopsis proteases have not been characterized at a biochemical level, nor have they been localized intracellularly. In this study, we characterized AtCEP2. A 3xHA-mCherry-AtCEP2 gene fusion including pro-peptide and KDEL targeting sequences expressed under control of the endogenous promoter enabled us to isolate AtCEP2 “ex vivo”. The purified protein was shown to be activated in a pH-dependent manner. After activation, however, protease activity was pH-independent. Analysis of substrate specificity showed that AtCEP2 accepts proline near the cleavage site, which is a rare feature specific for KDEL-CysEPs. mCherry-AtCEP2 was detected in the epidermal layers of leaves, hypocotyls and roots; in the root, it was predominantly found in the elongation zone and root cap. Co-localization with an ER membrane marker showed that mCherry-AtCEP2 was stored in two different types of ER-derived organelles: 10 μm long spindle shaped organelles as well as round vesicles with a diameter of approximately 1 μm. The long organelles appear to be ER bodies, which are found specifically in Brassicacae. The round vesicles strongly resemble the ricinosomes first described in castor bean. This study provides a first evidence for the existence of ricinosomes in Arabidopsis, and may open up new avenues of research in the field of PCD and developmental tissue remodeling. Electronic supplementary material The online version of this article (doi:10.1007/s11103-013-0157-6) contains supplementary material, which is available to authorized users.

International audience; Pythium oligandrum, a non-pathogenic soil-inhabiting oomycete, colonizes the root ecosystem of many crop species. Whereas most members in the genus Pythium are plant pathogens, P. oligandrum distinguishes itself from the pathogenic species by its ability to protect plants from biotic stresses in addition to promoting plant growth. The success of P. oligandrum at controlling soilborne pathogens is partly associated with direct antagonism mediated by mycoparasitism and antimicrobial compounds. Interestingly, P. oligandrum has evolved with specific mechanisms to attack its prey even when these belong to closely related species. Of particular relevance is the question of how P. oligandrum distinguishes between self- and non-self cell wall degradation during the mycoparasitic process of pathogenic oomycete species. The ability of P. oligandrum to enter and colonize the root system before rapidly degenerating is one of the most striking features that differentiate it from all other known biocontrol fungal agents. In spite of this atypical behaviour, P. oligandrum sensitizes the plant to defend itself through the production of at least two types of microbe-associated molecular patterns, including oligandrin and cell wall protein fractions, which appear to be closely involved in the early events preceding activation of the jasmonic acid- and ethylene-dependent signalling pathways and subsequent localized and systemic induced resistance. The aim of this review is to highlight the expanding knowledge of the mechanisms by which P. oligandrum provides beneficial effects to plants and to explore the potential use of this oomycete or its metabolites as new disease management strategies.

Although the cross-talk between auxin and ethylene has been described during plant development, the role played by auxin upon gene expression during aerenchyma formation is poorly understood. Root aerenchyma formation results from the opening of gas spaces in the cortex. It is part of a developmental program (constitutive) or due to ethylene treatment or abiotic stress (induced) such as flooding and nutrient starvation. This process relies on programmed cell death and cell wall modifications. Here we followed development of aerenchyma formation in sugarcane along 5 cm from the root apex. As a constitutive process, the aerenchyma formation was observed in the cortex from the 3rd cm onwards. This occurred despite 1-methylcyclepropene (1-MCP) treatment, an inhibitor of ethylene perception. However, this process occurred while ethylene (and auxin) levels decreased. Within the aerenchyma formation zone, the concentration of ethylene is lower in comparison to the concentration in maize. Besides, the ratio between both hormones (ethylene and auxin) was around 1:1. These pieces of evidence suggest that ethylene sensitivity and ethylene-auxin balance may play a role in the formation of aerenchyma. Furthermore, the transcriptional analysis showed that genes related to cell expansion are up-regulated due to 1-MCP treatment. Our results help explaining the regulation of the formation constitutive aerenchyma in sugarcane.

Fruit softening has been largely associated with cell wall degradation by a number of loosening proteins. Firmness is a major quality attribute of fresh cherries and also an important factor affecting the susceptibility to postharvest rots. By analyzing the solubilization, depolymerization and composition of pectins and hemicelluloses in cultivars with contrasting firmness we found that the pattern and extent of their wall disassembly was quite similar. No marked pectin or hemicellulose depolymerization was observed and a similar reduction in tightlybound pectins and hemicellulose was detected in both cultivars during ripening. However, firm cherries presented pectic polymers with lower proportion of neutral sugars compared to uronic acids, suggesting that the variation in total wall polysaccharide and the branching of pectins assembled early in development or the proportion of homogalacturonan (HG) to type rhamnogalacturonan-I (RG-I) may contribute to the differences in firmness between cultivars. Dismantling of the cell wall by the action of relatively "well known" loosening agents is involved in the progressive softening occurring during ripening. Two of these proteins include polygalacturonases (PG) which are known to hydrolyze homogalacturonans and expansins (Exp) believed to participate in the relaxation of the cell wall by reducing hydrogen bonding between cellulose microfibrils and xyloglucan. We investigated the in vivo roles of these wall-disassembling proteins, by overexpressing PG and Exp1 both alone and in combination in a non-ripening rin tomato background. The simultaneous overexpression of PG and Exp1 in rin fruit restored softening in these non-ripening fruit. Unexpectedly, PG overexpression resulted in higher hemicellulose depolymerization while increased levels of Exp1 accelerated pectin turnover. This shows that besides their "well known" in vitro functions these proteins act in muro by facilitating the degradation of non-directly targeted wall components, likely by increasing the accessibility of pre-existing wall-degrading proteins to their polysaccharide substrates. Fil: Vicente, Ariel Roberto. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina Fil: Rodoni, Luis Maria. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina Fil: Salato, Gloria Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentina Fil: Basanta, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentina Fil: Ponce, Nora Marta Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentina Fil: Stortz, Carlos Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentina Fil: Raffo Benegas, María Dolores. Instituto Nacional de Tecnología Agropecuaria; Argentina Fil: Powell, A. L. T.. University of California; Estados Unidos Fil: Bennett, A. B.. University of California; Estados Unidos Fil: Labavitch, J. M.. University of California; Estados Unidos

Anaerobic digestion (AD) of microalgae is primarily inhibited by the chemical composition of their cell walls containing biopolymers able to resist bacterial degradation. Adoption of pre-treatments such as thermal, thermal hydrolysis, ultrasound and enzymatic hydrolysis have the potential to remove these inhibitory compounds and enhance biogas yields by degrading the cell wall, and releasing the intracellular algogenic organic matter (AOM). This work investigated the effect of four pre-treatments on three microalgae species, and their impact on the quantity of soluble biomass released in the media and thus on the digestion process yields. The analysis of the composition of the soluble COD released and of the TEM images of the cells showed two main degradation actions associated with the processes: (1) cell wall damage with the release of intracellular AOM (thermal, thermal hydrolysis and ultrasound) and (2) degradation of the cell wall constituents with the release of intracellular AOM and the solubilisation of the cell wall biopolymers (enzymatic hydrolysis). As a result of this, enzymatic hydrolysis showed the greatest biogas yield increments (>270%) followed by thermal hydrolysis (60–100%) and ultrasounds (30–60%).

C NMR to determine which type of loose chemical compounds were produced by the thermal treatment. The formation of some toxic polynuclear aromatic hydrocarbons derivatives of phenantrene as well as other classes of polyaromatics compounds was detected. It is most likely that the presence of all such compounds contributes, perhaps to a relatively substantial extent, to the reported resistance of heat treated timber to fungal and other biological attack. Other allegedly non-toxic compounds due to wood constituents degradation were also found, mainly the by-products of lignin pyrolysis. The extent of toxic and non-toxic compounds in the heat treated wood were not quantified, but it can be stated that their proportion appears to be quite small. The lack of quantification of the concentration of these products does not allow to ascertain if the final product is toxic or not, and to what extent. Nonetheless, the amount of polynuclear aromatic hydrocarbon-type derivatives should be quantified and related to the type of heat treatment process undertaken before assigning to this type of wood treatment a completely clean health safety label.

To investigate the modification of cell wall polysaccharides in relation to aril breakdown in harvested longan fruit, three pectin fractions (WSP, water soluble pectin; CSP, CDTA-soluble pectin; ASP, alkali soluble pectin) and one hemicellulose fraction (4 M KOH-SHC, 4 M KOH-soluble hemicellulose) were extracted, and their contents, monosaccharide compositions and molecular weights were evaluated. As aril breakdown intensified, CSP content increased while ASP and 4 M KOH-SHC contents decreased, suggesting the solubilization and conversion of cell wall components. Furthermore, the molar percentage of arabinose (Ara), as the main component of the side-chains, decreased largely in CSP and ASP while that of rhamnose (Rha), as branch point for the attachment of neutral sugar side chains, increased during aril breakdown. Analysis of (Ara + Gal)/Rha ratio showed that the depolymerization of CSP and ASP happened predominantly in side-chains formed of Ara residues. For 4 M KOH-SHC, more backbones were depolymerized during aril breakdown. Moreover, it was found that the molecular weights of CSP, ASP and 4 M KOH-SHC polysaccharides tended to decrease as aril breakdown intensified. These results suggest that both enhanced depolymerization and structural modifications of polysaccharides in the CSP, ASP and 4 M KOH-SHC fractions might be responsible for aril breakdown of harvested longan fruit.

Biotechnology for biofuels 6, 53 (2013). doi:10.1186/1754-6834-6-53, Published by BioMed Central, London

Tomato fruit (cv. ‘Sunny’) were harvested at the mature green stage and kept for 4 days at either 21°C or 40°C, then subsequently stored at 21°C. Red color development was inhibited in heated fruit, as was softening. Fourteen days after treatment, heat-stressed fruit were twice as firm as the controls. The cell wall uronide content increased in heat-exposed fruit while remaining unchanged in samples stored constantly at 21°C. Heat treatment inhibited ripening-associated cell wall modification so that 14 days after treatment, stressed fruit contained only one-third the amount of soluble polyuronides that was present in the control fruit. Furthermore, the rate of loss of cell wall galactose and arabinose was reduced in heat-stressed tomatoes. Postharvest exposure of unripe tomato fruit to high temperature appears to reduce the rate of cell wall degradation, while the synthesis of polyuronide components continues normally.

Physical methods, such as electron microscopy, provide information on the distribution of cell wall constituents both within and between cell walls. Electron microscopy allows visualization of the ease of breakdown of different plant tissues and their selective attack by rumen microorganisms. This technique also provides information on the way in which microorganisms, in particular the recently discovered anaerobic fungi, are attached to plant tissues.

Olive fruits at three stages of ripening (green, cherry, and black) have been studied. After cell wall isolation, the compositions of the cell wall and that of the phosphate-soluble polysaccharides were determined. In cell walls, decreases in arabinose, xylose, glucose, and uronic acid levels were observed, together with a slight increase in mannose on ripening. At the beginning of ripening, fragments of pectic polymers were the major constituents of the phosphate-soluble fraction, with the hemicellulosic ones increasing toward the end of the process. The molecular weight of the fragments solubilized was approximately 6 kDa. After cell wall fractionation, the pectic polysaccharides soluble in imidazole and sodium carbonate were also studied. In both fractions, between the green and cherry stages of ripening, a significant loss of homogalacturonans took place. Between the cherry and black stages of ripening, rhamnogalacturonan side chains were also released in addition to homogalacturonans. In any of the pectic fractions, changes in apparent molecular weight were quantified.

The results of recent technological developments in light and scanning electron microscopy closely used for research on forage cell wall degradation in ruminants, are reviewed. The indigestibility of forages by rumen microorganisms used to be ascribed mainly to an overall presence of lignin in the plant material. However, early light microscopic observations without application of histochemical staining revealed that some leaf and stem tissues were degraded completely. The early use of lignin detecting dyes, such as acid phloroglucinol or safranin, in light microscopy made it possible to discriminate between lignified undegradable and unlignified degradable plant tissues. The introduction of the scanning electron microscope enabled a further discrimination between degradable and undegradable cell wall and cell wall layers in plant tissues. As a result of continuous improvement of the techniques used in microscopy, e.g. section to slide, mirror sectioning, microspectrophotometry and cryo-ultramilling, forage indigestibility can now be attributed to the specific deposition and location of cutin/suberin or lignin layers inside the plant cell wall. These structural layers form barriers hindering access of rumen microorganisms to degradable parts of the cell wall.

Propagules from macroconidial cultures of Fusarium solani f. cucurbitae in vitro were examined at intervals during chlamydospore formation by transmission electron microscopy. There was a gradual breakdown of the original macroconidial cell wall. Simultaneously, synthesis of new cell wall material occurred. The significance of autolytic cell wall degradation as it affects the morphology of chlamydospores formed from macroconidial cells in soil is discussed.

Plant cell walls are organized into complex matrices composed primarily of carbohydrates that represent a potential energy source for ruminants. An overview of the basic structural features of the major groups of polysaccharides that make up forage cell walls, metabolic changes during cell wall development, cell wall component interactions, and some aspects of cell wall degradation are presented. Polysaccharide components that compose the cell wall matrix can be disassociated and fractionated according to similar physio-chemical properties

Degradation of cell walls in elm wood tissue (Ulmus americand) by aggressive and non-aggressive isolates of Ophiostoma ulmi was studied by scanning electron microscopy. Xylem vessel walls were much more affected after infection with the aggressive isolate than after infection with the non-aggressive one.

Publisher Summary Many species of white rot fungi can selectively degrade lignin from coniferous and deciduous wood without extensive loss of cellulose. The patterns of cell wall degradation are distinct from the decay patterns caused by other white rot fungi that simultaneously degrade all cell wall components, as well as from other types of decay. Advanced stages of decayed wood that is lignin free can easily be identified in the field and laboratory using various histological reagents. These reagents result in color changes that aid in macroscopic observations and identification of delignified wood. This chapter discusses the morphological aspects of wood degradation. Micromorphological and ultrastructural techniques are needed for precise determinations and to identify the sequential changes that occur during the process of lignin degradation within woody cell walls. The spatial relationships between fungal enzymes and sites of cell wall attack can be elucidated using these techniques. The chapter discusses the quantitative data on lignin distribution in different morphological regions of the cell wall that can be obtained by coupling scanning electron microscopy with energy-dispersive X-ray analysis.