Arabidopsis leucine-rich repeat extensin (LRX) proteins modify cell wall composition and influence plant growth

BACKGROUND: Leucine-rich repeat extensins (LRXs) are extracellular proteins consisting of an N-terminal leucine-rich repeat (LRR) domain and a C-terminal extensin domain containing the typical features of this class of structural hydroxyproline-rich glycoproteins (HRGPs). The LRR domain is likely to bind an interaction partner, whereas the extensin domain has an anchoring function to insolubilize the protein in the cell wall. Based on the analysis of the root hair-expressed LRX1 and LRX2 of Arabidopsis thaliana, LRX proteins are important for cell wall development. The importance of LRX proteins in non-root hair cells and on the structural changes induced by mutations in LRX genes remains elusive. RESULTS: The LRX gene family of Arabidopsis consists of eleven members, of which LRX3, LRX4, and LRX5 are expressed in aerial organs, such as leaves and stem. The importance of these LRX genes for plant development and particularly cell wall formation was investigated. Synergistic effects of mutations with gradually more severe growth retardation phenotypes in double and triple mutants suggest a similar function of the three genes. Analysis of cell wall composition revealed a number of changes to cell wall polysaccharides in the mutants. CONCLUSIONS: LRX3, LRX4, and LRX5, and most likely LRX proteins in general, are important for cell wall development. Due to the complexity of changes in cell wall structures in the lrx mutants, the exact function of LRX proteins remains to be determined. The increasingly strong growth-defect phenotypes in double and triple mutants suggests that the LRX proteins have similar functions and that they are important for proper plant development

Water Deficit-Responsive QTLs for Cell Wall Degradability and Composition in Maize at Silage Stage

The use of lignocellulosic biomass for animal feed or biorefinery requires the optimization of its degradability. Moreover, biomass crops need to be better adapted to the changing climate and in particular to periods of drought. Although the negative impact of water deficit on biomass yield has often been mentioned, its impact on biomass quality has only been recently reported in a few species. In the present study, we combined the mapping power of a maize recombinant inbred line population with robust near infrared spectroscopy predictive equations to track the response to water deficit of traits associated with biomass quality. The population was cultivated under two contrasted water regimes over 3 consecutive years in the south of France and harvested at silage stage. We showed that cell wall degradability and β-O-4-linked H lignin subunits were increased in response to water deficit, while lignin and p-coumaric acid contents were reduced. A mixed linear model was fitted to map quantitative trait loci (QTLs) for agronomical and cell wall-related traits. These QTLs were categorized as “constitutive” (QTL with an effect whatever the irrigation condition) or “responsive” (QTL involved in the response to water deficit) QTLs. Fifteen clusters of QTLs encompassed more than two third of the 213 constitutive QTLs and 13 clusters encompassed more than 60% of the 149 responsive QTLs. Interestingly, we showed that only half of the responsive QTLs co-localized with constitutive and yield QTLs, suggesting that specific genetic factors support biomass quality response to water deficit. Overall, our results demonstrate that water deficit favors cell wall degradability and that breeding of varieties that reconcile improved drought-tolerance and biomass degradability is possible

Cell adhesion in plants is under the control of putative O-fucosyltransferases

Cell-to-cell adhesion in plants is mediated by the cell wall and the presence of a pectin-rich middle lamella. However, we know very little about how the plant actually controls and maintains cell adhesion during growth and development and how it deals with the dynamic cell wall remodeling that takes place. Here we investigate the molecular mechanisms that control cell adhesion in plants. We carried out a genetic suppressor screen and a genetic analysis of cell adhesion-defective Arabidopsis thaliana mutants. We identified a genetic suppressor of a cell adhesion defect affecting a putative O-fucosyltransferase. Furthermore, we show that the state of cell adhesion is not directly linked with pectin content in the cell wall but instead is associated with altered pectin-related signaling. Our results suggest that cell adhesion is under the control of a feedback signal from the state of the pectin in the cell wall. Such a mechanism could be necessary for the control and maintenance of cell adhesion during growth and development

Cell adhesion in plants is under the control of putative O-fucosyltransferases

Cell-to-cell adhesion in plants is mediated by the cell wall and the presence of a pectin-rich middle lamella. However, we know very little about how the plant actually controls and maintains cell adhesion during growth and development and how it deals with the dynamic cell wall remodeling that takes place. Here we investigate the molecular mechanisms that control cell adhesion in plants. We carried out a genetic suppressor screen and a genetic analysis of cell adhesion-defective Arabidopsis thaliana mutants. We identified a genetic suppressor of a cell adhesion defect affecting a putative O-fucosyltransferase. Furthermore, we show that the state of cell adhesion is not directly linked with pectin content in the cell wall but instead is associated with altered pectin-related signaling. Our results suggest that cell adhesion is under the control of a feedback signal from the state of the pectin in the cell wall. Such a mechanism could be necessary for the control and maintenance of cell adhesion during growth and development

Influence of chemical treatments of miscanthus stem fragments on polysaccharide release in the presence of cement and on the mechanical properties of bio-based concrete materials

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Polyethylene composites made from below-ground miscanthus biomass

International audienceMiscanthus is a perennial grass which may be interesting for the composite industrial sector. When the cycle of the crop comes to the end, the biomass below ground need to be valorized. One never-studied topic is to evaluate its potential valorization as composites. Below-ground (rhizomes plus roots) biomass of Miscanthus × giganteus cultivated on three different blocks with three different nitrogen fertilization levels were collected, ground, sieved and used as fillers in a polyethylene matrix. Miscanthus rhizome plus roots fragments have a very low axial ratio around two, in contrast with stem fragments which are three to four times more elongated. The mechanical properties of composites filed with rhizome plus roots fragments are much below the ones of the composites filled with stem fragments. The tensile strength is about half the values of stem composites (7.4 MPa for rhizomes compared with 13 MPa for stems) and there is a very large drop of the Young’s modulus, down to 260 MPa compared with 900–1000 MPa for stems. Only impact strength has good values (6–7 kJ/m2). The very low aspect ratio of the rhizome fragments combined with the fact that there are twice more cellulose in stems than in rhizomes with a non cellulosic polysaccharides-cellulose ratio being twice larger for rhizomes (about 1 for rhizomes and 0.45 for stems) are both acting in the same direction of lowering the mechanical properties of rhizome fragment-based polymer composites. These low mechanical properties are restricting the use of such composites to applications were the low cost is the main factor of choice

Effects of the nature of atmosphere during thermal treatment on chemical compositions and properties of miscanthus. Application to miscanthus-filled concrete

International audienceAmong the difficulties of preparation of ligno-cellulosic biomass-filled concrete are its hygroscopicity, its sensitivity to degradation in strong alkaline media and its probable low resistance to micro-organisms. Among the many methods have been explored and tested to solve these difficulties. We are reporting here the use of high temperature thermal treatment. We applied heat on miscanthus with the hope to reduce hygroscopicity, enhance alkali resistance and dimensional stability, without using any chemical treatment. The effects of heat treatment atmosphere on chemical modifications and behaviours of treated miscanthus were investigated. The parameters which were varied were atmospheres (vacuum and nitrogen), time and treatment temperature. Mass loss, with closely related to the degree of miscanthus modifications is the parameter used to control the treatment conditions. At the same treatment intensity, miscanthus treated under nitrogen has lower mass loss than those treated under vacuum. Under vacuum, volatile degraded products are continuously removed, which can help to stop their recondensation or cross linking reactions occurring on the surface of miscanthus stems. Reductions in water absorption and in mass loss in alkali medium with thermally treated Miscanthus are observed. The hydrophilicity of treated miscanthus is expected to decrease. The resulting products likely have an improvement in decay resistance due to the removal of hemicelluloses which are low stability and are mostly degraded during treatment. At elevated temperature, cellulose and lignin are also modified. After thermal treatment, miscanthus chips were used to prepare lightweight concrete blocks with a common Portland cement as a binder. The amount of sugars released during concrete preparation process, which can contribute to the inhibition of cement hydration or delay in cement setting time, was determined. The interactions between miscanthus chips and cement were characterised. We will evaluate the potential of this method for improving concrete preparation

Influence of the chemical composition on the thermal properties of miscanthus

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GDP-L-fucose is required for boundary definition in plants

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