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Rhamnogalacturonan II (RG-II) is a structurally complex and conserved domain of the pectin present in the primary cell walls of vascular plants. Borate cross-linking of RG-II is required for plants to grow and develop normally. Mutations that alter RG-II structure also affect cross-linking and are lethal or severely impair growth. Thus, few genes involved in RG-II synthesis have been identified. Here, we developed a method to generate viable loss-of-function Arabidopsis (Arabidopsis thaliana) mutants in callus tissue via CRISPR/Cas9-mediated gene editing. We combined this with a candidate gene approach to characterize the male gametophyte defective 2 (MGP2) gene that encodes a putative family GT29 glycosyltransferase. Plants homozygous for this mutation do not survive. We showed that in the callus mutant cell walls, RG-II does not cross-link normally because it lacks 3-deoxy-D-manno-octulosonic acid (Kdo) and thus cannot form the α-L-Rhap-(1→5)-α-D-kdop-(1→sidechain). We suggest that MGP2 encodes an inverting RG-II CMP-β-Kdo transferase (RCKT1). Our discovery provides further insight into the role of sidechains in RG-II dimerization. Our method also provides a viable strategy for further identifying proteins involved in the biosynthesis of RG-II.

BACKGROUND: Sclerotinia spp. are generalist fungal pathogens, infecting over 700 plant hosts worldwide, including major crops. While host resistance is the most sustainable and cost-effective method for disease management, complete resistance to Sclerotinia diseases is rare. We recently identified soft basal stem as a potential susceptibility factor to Sclerotinia minor infection in lettuce (Lactuca sativa) under greenhouse conditions. RESULTS: Analysis of stem and root cell wall composition in five L. sativa and one L. serriola accessions with varying growth habits and S. minor resistance levels revealed strong association between hemicellulose constituents, lignin polymers, disease phenotypes, and basal stem mechanical strength. Accessions resistant to basal stem degradation consistently exhibited higher levels of syringyl, guaiacyl, and xylose, but lower levels of fucose in stems. These findings suggest that stem cell wall polymers recalcitrant to breakdown by lignocellulolytic enzymes may contribute to stem strength-mediated resistance against S. minor. CONCLUSIONS: The lignin content, particularly guaiacyl and syringyl, along with xylose could potentially serve as biomarkers for identifying more resistant lettuce accessions and breeding lines. Basal stem degradation by S. minor was influenced by localized microenvironment conditions around the stem base of the plants.

The molecular foundations of epidermal cell wall mechanics are critical for understanding structure-function relationships of primary cell walls in plants and facilitating the design of bioinspired materials. To uncover the molecular mechanisms regulating the high extensibility and strength of the cell wall, the onion epidermal wall is stretched uniaxially to various strains and cell wall structures from mesoscale to atomic scale are characterized. Upon longitudinal stretching to high strain, epidermal walls contract in the transverse direction, resulting in a reduced area. Atomic force microscopy shows that cellulose microfibrils exhibit orientation-dependent rearrangements at high strains: longitudinal microfibrils are straightened out and become highly ordered, while transverse microfibrils curve and kink. Small-angle X-ray scattering detects a 7.4 nm spacing aligned along the stretch direction at high strain, which is attributed to distances between individual cellulose microfibrils. Furthermore, wide-angle X-ray scattering reveals a widening of (004) lattice spacing and contraction of (200) lattice spacing in longitudinally aligned cellulose microfibrils at high strain, which implies longitudinal stretching of the cellulose crystal. These findings provide molecular insights into the ability of the wall to bear additional load after yielding: the aggregation of longitudinal microfibrils impedes sliding and enables further stretching of the cellulose to bear increased loads.

Every fungal cell is encapsulated in a cell wall, essential for cell viability, morphogenesis, and pathogenesis. Most knowledge of the cell wall composition in fungi has focused on ascomycetes, especially human pathogens, but considerably less is known about early divergent fungal groups, such as species in the Zoopagomycota and Mucoromycota phyla. To shed light on evolutionary changes in the fungal cell wall, we studied the monosaccharide composition of the cell wall of 18 species including early diverging fungi and species in the Basidiomycota and Ascomycota phyla with a focus on those with pathogenic lifestyles and interactions with plants. Our data revealed that chitin is the most characteristic component of the fungal cell wall, and was found to be in a higher proportion in the early divergent groups. The Mucoromycota species possess few glucans, but instead have other monosaccharides such as fucose and glucuronic acid that are almost exclusively found in their cell walls. Additionally, we observed that hexoses (glucose, mannose and galactose) accumulate in much higher proportions in species belonging to Dikarya. Our data demonstrate a clear relationship between phylogenetic position and fungal cell wall carbohydrate composition and lay the foundation for a better understanding of their evolution and their role in plant interactions.

Modification of lignin in feedstocks via genetic engineering aims to reduce biomass recalcitrance to facilitate efficient conversion processes. These improvements can be achieved by expressing exogenous enzymes that interfere with native biosynthetic pathways responsible for the production of the lignin precursors. In-planta expression of a 3-dehydroshikimate dehydratase (QsuB) in poplar trees reduced lignin content and altered their monomer composition, which enabled higher yields of sugars after cell wall polysaccharide hydrolysis. Understanding how plants respond to such genetic modifications at the transcriptional and metabolic levels is needed to facilitate further improvement and field deployment. In this work, we amassed fundamental knowledge on lignin-modified QsuB poplar using RNA-seq and metabolomics. The data clearly demonstrate that changes in gene expression and metabolite abundance can occur in a strict spatiotemporal fashion, revealing tissue-specific responses in the xylem, phloem, or periderm. In the poplar line that exhibits the strongest reduction in lignin, we found that 3% of the transcripts had altered expression levels and ~19% of the detected metabolites had differential abundance in the xylem from older stems. Changes affect predominantly the shikimate and phenylpropanoid pathways as wells as secondary cell wall metabolism, and result in significant accumulation of hydroxybenzoates derived from protocatechuate and salicylate.

Many insects have evolved the ability to manipulate plant growth to generate extraordinary structures called galls, in which insect larva can develop while being sheltered and feeding on the plant. In particular, cynipid (Hymenoptera: Cynipidae) wasps have evolved to form morphologically complex galls and generate an astonishing array of gall shapes, colors, and sizes. However, the biochemical basis underlying these remarkable cellular and developmental transformations remains poorly understood. A key determinant in plant cellular development is cell wall deposition that dictates the physical form and physiological function of newly developing cells, tissues, and organs. However, it is unclear to what degree cell walls are restructured to initiate and support the formation of new gall tissue. Here, we characterize the molecular alterations underlying gall development using a combination of metabolomic, histological, and biochemical techniques to elucidate how valley oak (Quercus lobata) leaf cells are reprogrammed to form galls. Strikingly, gall development involves an exceptionally coordinated spatial deposition of lignin and xylan to form de novo gall vasculature. Our results highlight how cynipid wasps can radically change the metabolite profile and restructure the cell wall to enable the formation of galls, providing insights into the mechanism of gall induction and the extent to which plants can be entirely reprogrammed to form unique structures and organs.

The cell wall integrity (CWI) signaling pathway regulates yeast cell wall biosynthesis, cell division, and responses to external stress. The cell wall, comprised of a dense network of chitin, β-1,3- and β-1,6- glucans, and mannoproteins, is very thin,

Crown gall disease (Agrobacterium tumefaciens), crown/root rot disease (Phytophthora spp.), root lesion disease (Pratylenchus vulnus) and tree vigor are key traits affecting the productivity and quality of walnuts in California. Unchallenged hybrid rootstocks were analyzed by RNA-seq to examine pre-formed factors affecting these traits. Enrichment analysis of the differentially expressed genes revealed that the increased expression of cell wall biogenesis-related genes plays a key role in susceptibility to A. tumefaciens, susceptibility to Phytophthora spp. and increased vigor. Analysis of the predicted subcellular loci of the encoded proteins revealed that many gene products associated with vigor and susceptibility were targeted to the plasma membrane and extracellular space, connecting these traits to sustaining barrier function. We observed that RNA processing and splicing, along with predicted nuclear targeting, were associated with resistance to A. tumefaciens, resistance to Phytophthora spp. and low vigor. Four genes within the J. microcarpa QTL region for resistance to A. tumefaciens and Phytophthora spp. were represented among our transcripts, with two of the genes being differentially expressed in association with resistance to A. tumefaciens and decreased vigor. No differential expression related to Phytophthora spp. or P. vulnus resistance was observed in this region. Additionally, the J. microcarpa haplotype expressed more transcripts associated with resistance to A. tumefaciens, Phytophthora spp. and low vigor, but not P. vulnus, than the J. regia haplotype. We also report unique and shared hormone and defense responses associated with each trait. This research suggests a link between cell wall biogenesis, vigor and critical root diseases of walnut.

Plant roots integrate environmental signals with development using exquisite spatiotemporal control. This is apparent in the deposition of suberin, an apoplastic diffusion barrier, which regulates flow of water, solutes and gases, and is environmentally plastic. Suberin is considered a hallmark of endodermal differentiation but is absent in the tomato endodermis. Instead, suberin is present in the exodermis, a cell type that is absent in the model organism Arabidopsis thaliana. Here we demonstrate that the suberin regulatory network has the same parts driving suberin production in the tomato exodermis and the Arabidopsis endodermis. Despite this co-option of network components, the network has undergone rewiring to drive distinct spatial expression and with distinct contributions of specific genes. Functional genetic analyses of the tomato MYB92 transcription factor and ASFT enzyme demonstrate the importance of exodermal suberin for a plant water-deficit response and that the exodermal barrier serves an equivalent function to that of the endodermis and can act in its place.

Summary: Bamboo, a renewable resource with rapid growth and an impressive height‐to‐diameter ratio, faces mechanical instability due to its slender structure. Despite this, bamboo maintains its posture without breaking in its battle against environmental and gravitational forces. But what drives this motor function in bamboo?This study subjected Moso bamboo (Phyllostachys edulis) to gravitational stimulation, compelling it to grow at a 45° angle instead of upright. Remarkably, the artificially inclined bamboo exhibited astonishing shape control and adjustment capabilities.The growth strain was detected at both macroscopic and microscopic levels, providing evidence for the presence of internal stress, namely growth stress. The high longitudinal tensile stress on the upper side, along with a significant asymmetry in stress distribution in tilted bamboo, plays a pivotal role in maintaining its mechanical stability.Drawing upon experimental findings, it can be deduced that the growth stress primarily originates from the broad layers of fiber cells. Bamboo could potentially regulate the magnitude of growth stress by modifying the number of fiber cell layers during its maturation process. Additionally, the microfibril angle and lignin disposition may decisively influence the generation of growth stress. [ABSTRACT FROM AUTHOR]

The study of microorganism interactions is important for understanding the organization and functioning of microbial consortia. Additionally, the interaction between yeast and bacteria is of interest in the field of health and nutrition area for the development of probiotics. To investigate these microbial interactions at the cellular and molecular levels, a simple, reliable, and quantitative method is proposed. We demonstrated that flow cytometry enables the measurement of interactions at a single-cell level by detecting and counting yeast cells with bound fluorescent bacteria. Imaging flow cytometry revealed that the number of bacteria attached to yeast followed a Gaussian distribution whose maximum reached 14 bacterial cells using a clinical Escherichia coli strain E22 and the laboratory yeast strain BY4741. We found that the dynamics of adhesion resemble a Langmuir adsorption model, albeit it is a rapid and almost irreversible process. This adhesion is dependent on the mannose-specific type 1 fimbriae, as E. coli mutants lacking these appendages no longer adhere to yeast. However, this type 1 fimbriae-dependent adhesion could involve additional yeast cell wall factors, since the interaction between bacteria and yeast mutants with altered mannan content remained comparable to that of wild-type yeast. In summary, flow cytometry is an appropriate method for studying bacteria-yeast adhesion, as well as for the high-throughput screening of candidate molecules likely to promote or counteract this interaction. [ABSTRACT FROM AUTHOR]

Although many of the structures and organelles of vegetative cells are comparable to those of animal tissues, significant differences between the two kingdoms require modifications in histological techniques for both tissue processing steps and histochemical staining techniques. The authors investigated the challenges of working with plant tissues by collecting various flora to represent the four main plant organs: leaf, stem, root, and flower/fruit. Triplicate samples for each specimen were placed into formalin for paraffin embedding, placed into formalin for later frozen sections, and used fresh to undergo immediate frozen sectioning. Frozen sections of plant tissues were more difficult to obtain than formalin-fixed paraffin-embedded (FFPE) sections, exhibited tissue loss during staining, and were inferior morphologically to FFPE sections. Although, historically, plant tissue fixation and processing has employed several different reagents compared with those used in animal tissue processing and took significantly longer times, the current investigation determined reagents and protocols from a modern histology laboratory which processes mammalian tissues can be applied to plant tissue processing with only slight modifications in respect to reagent timing. Additionally, staining techniques were compared and while it is well known that plant cell walls stain well with safranin O, the current investigation determined the uptake of safranin O can be accelerated by incubating at 60°C. [ABSTRACT FROM AUTHOR]

Plant cell walls are a critical site where plants and pathogens continuously struggle for physiological dominance. Here we show that dynamic remodeling of pectin methylesterification of plant cell walls is a component of the physiological and co-evolutionary struggles between hosts and pathogens. A pectin methylesterase (PsPME1) secreted by Phytophthora sojae decreases the degree of pectin methylesterification, thus synergizing with an endo-polygalacturonase (PsPG1) to weaken plant cell walls. To counter PsPME1-mediated susceptibility, a plant-derived pectin methylesterase inhibitor protein, GmPMI1, protects pectin to maintain a high methylesterification status. GmPMI1 protects plant cell walls from enzymatic degradation by inhibiting both soybean and P. sojae pectin methylesterases during infection. However, constitutive expression of GmPMI1 disrupted the trade-off between host growth and defense responses. We therefore used AlphaFold structure tools to design a modified form of GmPMI1 (GmPMI1R) that specifically targets and inhibits pectin methylesterases secreted from pathogens but not from plants. Transient expression of GmPMI1R enhanced plant resistance to oomycete and fungal pathogens. In summary, our work highlights the biochemical modification of the cell wall as an important focal point in the physiological and co-evolutionary conflict between hosts and microbes, providing an important proof of concept that AI-driven structure-based tools can accelerate the development of new strategies for plant protection. Plant pectin methylesterase inhibitors (PMEIs) influence pathogen susceptibility and plant growth by regulating pectin methyl esterification. However, constitutive expression of PMEIs can disrupt cell-wall composition, leading to significant tradeoffs between growth and defense. AlphaFold-guided redesign of GmPMI1 produced a modified PMEI that specifically targets and inhibits pectin methylesterases (PMEs) of P. sojae without interfering with the developmental functions of plant PMEs, thus increasing crop disease resistance. [ABSTRACT FROM AUTHOR]

Summary: The role of maternal tissue in embryogenesis remains enigmatic in many complex organisms. Here, we investigate the contribution of maternal tissue to apical–basal patterning in the kelp embryo.Focussing on Undaria pinnatifida, we studied the effects of detachment from the maternal tissue using microsurgery, staining of cell wall modifications, morphometric measurements, flow cytometry, genotyping and a modified kelp fertilisation protocol synchronising kelp embryogenesis.Detached embryos are rounder and often show aberrant morphologies. When a part of the oogonial cell wall remains attached to the zygote, the apical–basal patterning is rescued. Furthermore, the absence of contact with maternal tissue increases parthenogenesis, highlighting the critical role of maternal signals in the initial stages of development.These results show a key role for the connection to the maternal oogonial cell wall in apical–basal patterning in kelps. This observation is reminiscent of another brown alga, Fucus, where the cell wall directs the cell fate. Our findings suggest a conserved mechanism across phylogenetically distant oogamous lineages, where localised secretion of sulphated F2 fucans mediates the establishment of the apical–basal polarity. In this model, the maternal oogonial cell wall mediates basal cell fate determination by providing an extrinsic patterning cue to the future kelp embryo. [ABSTRACT FROM AUTHOR]

The limited availability of efficient treatments for Candida infections and the increased emergence of antifungal-resistant strains stimulates the search for new antifungal agents. We have previously isolated a sunflower mannose-binding lectin (Helja) with antifungal activity against Candida albicans , capable of binding mannose-bearing oligosaccharides exposed on the cell surface. This work aimed to investigate the biological and biophysical basis of Helja's binding to C. albicans cell wall mannans and its influence on the fungicidal activity of the lectin. We evaluated the interaction of Helja with the cell wall mannans extracted from the isogenic parental strain (WT) and a glycosylation-defective C. albicans with altered cell wall phosphomannosylation (mnn4 ∆ null mutants) and investigated its antifungal effect. Helja exhibited stronger antifungal activity on the mutant strain, showing greater inhibition of fungal growth, loss of cell viability, morphological alteration, and formation of clusters with agglutinated cells. This differential biological activity of Helja was correlated with the biophysical parameters determined by solid phase assays and isothermal titration calorimetry, which demonstrated that the lectin established stronger interactions with the cell wall mannans of the mnn4 ∆ null mutant than with the WT strain. In conclusion, our results provide new evidence on the nature of the Helja molecular interactions with cell wall components, i.e. phosphomannan, and its impact on the antifungal activity. This study highlights the relevance of plant lectins in the design of effective antifungal therapies. [ABSTRACT FROM AUTHOR]

Cellulose is the major renewable feedstock used in a variety of industrial processes. However, its native state, organizing itself in microfibrils and interacting with other components of the cell wall complex, forms a highly recalcitrant structure. Expansin proteins may facilitate the enzymatic saccharification stage by affecting non-covalent bonds between the wall polymers. In the current study, the expression profile of five selected Expansin genes from sugarcane, an important crop in the supply of biomass lignocellulose for the ethanol industry, was analyzed in leaves, roots, and young culms. The SacEXP32 and SacEXP39 genes, potentially associated with the cell wall architecture modification in sugarcane culm, were selected for functional characterization studies in Nicotiana benthamiana using the agroinfiltration assay. Heterologous expression of SacEXP32 and SacEXP39 revealed that N. benthamiana cellulose synthase gene was positively regulated at the transcript level in transformed tissue. However, only SacEXP32 expression increased cell area and enzymatic saccharification efficiency. SacEXP32 overexpression may have influenced the network of all cell wall polymers, indicating that this gene is a potential target for biotechnological approaches to improve plant biomass industrial processing. [ABSTRACT FROM AUTHOR]

BACKGROUND: Phytophthora capsici is a destructive oomycete pathogen, causing huge economic losses for agricultural production. The genus Trichoderma represents one of the most extensively researched categories of biocontrol agents, encompassing a diverse array of effective strains. The commercial biocontrol agent Trichoderma harzianum strain T‐22 exhibits pronounced biocontrol effects against many plant pathogens, but its activity against P. capsici is not known. RESULTS: T. harzianum T‐22 significantly inhibited the growth of P. capsici mycelia and the culture filtrate of T‐22 induced lysis of P. capsici zoospores. Electron microscopic analyses indicated that T‐22 significantly modulated the ultrastructural composition of P. capsici, with a severe impact on the cell wall integrity. Dual RNA sequencing revealed multiple biological processes involved in the inhibition during the interaction between these two microorganisms. In particular, a marked upregulation of genes was identified in T. harzianum that are implicated in cell wall degradation or disruption. Concurrently, the presence of T. harzianum appeared to potentiate the susceptibility of P. capsici to cell wall biosynthesis inhibitors such as mandipropamid and dimethomorph. Further investigations showed that mandipropamid and dimethomorph could strongly inhibit the growth and development of P. capsici but had no impact on T. harzianum even at high concentrations, demonstrating the feasibility of combining T. harzianum and these cell wall synthesis inhibitors to combat P. capsici. CONCLUSION: These findings provided enhanced insights into the biocontrol mechanisms against P. capsici with T. harzianum and evidenced compatibility between specific biological and chemical control strategies. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Main conclusion: The ultrastructural design and biochemical organization of the significantly thickened outer tissues of the gametophytic stem of Hypnodendron menziesii optimizes load bearing of the stem. Hypnodendron menziesii is a bryoid umbrella moss growing in high humid conditions on the forest floors of New Zealand. The erect gametophyte bears up to eight whorls of branches in succession, spreading across the stem that bears the heavy weight of branches with highly hydrated leaves. Our investigation using a combination of light microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and TEM-immunolabeling techniques provided novel information on the structural design and biochemical organization of greatly thickened cell walls of epidermal, hypodermal, and outermost cortical tissues, comparing underlying thin-walled cortical tissues in the gametophytic stem. Probing into the ultrastructure of the cell wall architecture of these target tissues by TEM and SEM revealed the cell walls to display a multilamellar organization, in addition to demonstrating the presence of an electron-dense substance in the cell wall, presumably flavonoids. The pattern of distribution and concentration of rhamnogalacturonan, homogalacturonan, and heteromannan, as determined by immunogold labeling, suggests that it is the combination of structural and molecular design of the cell wall that may optimize the mechanical function of the epidermal, hypodermal, and outer cortical tissues. Statistical relationships between the overall thickness of epidermal, hypodermal, and outer cortical cell walls, the lumen area of cells and the percentage area of cell wall occupied in these tissues at different heights of the stem, and thickness of secondary cell wall layers (L1-L4/5) were explored. The results of these analyses unequivocally support the contribution of outer tissues to the mechanical strength of the resilient stem. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is a biologically non-essential heavy metal, a major soil pollutant, and extremely harmful to plants. The phytohormone methyl jasmonate (MeJA) plays an important role in plant heavy-metal resistance. However, the understanding of the effects of MeJA supply level on alleviating Cd toxicity in plants is limited. Here, we investigated how MeJA regulated the development of physiological processes and cell wall modification in Cosmos bipinnatus. We found that low concentrations of MeJA increased the dry weight of seedlings under 120 µM Cd stress by reducing the transport of Cd from roots to shoots. Moreover, a threshold concentration of exogenous MeJA increased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in plant roots, the concentration of Cd in the root cell wall, and the contents of pectin and hemicellulose 1 polysaccharides, through converting Cd into pectin-bound forms. These results suggested that MeJA mitigated Cd toxicity by modulating root cell wall polysaccharide and functional group composition, especially through pectin polysaccharides binding to Cd, with effects on Cd transport capacity, specific chemical forms of Cd, and homeostatic antioxidant systems in C. bipinnatus. [ABSTRACT FROM AUTHOR]

Invasive fungal disease accounts for about 3.8 million deaths annually, an unacceptable rate that urgently prompts the discovery of new knowledge‐driven treatments. We report the use of camelid single‐domain nanobodies (Nbs) against fungal β‐1,3‐glucanosyltransferases (Gel) involved in β‐1,3‐glucan transglycosylation. Crystal structures of two Nbs with Gel4 from Aspergillus fumigatus revealed binding to a dissimilar CBM43 domain and a highly conserved catalytic domain across fungal species, respectively. Anti‐Gel4 active site Nb3 showed significant antifungal efficacy in vitro and in vivo prophylactically and therapeutically against different A. fumigatus and Cryptococcus neoformans isolates, reducing the fungal burden and disease severity, thus significantly improving immunocompromised animal survival. Notably, C. deneoformans (serotype D) strains were more susceptible to Nb3 and genetic Gel deletion than C. neoformans (serotype A) strains, indicating a key role for β‐1,3‐glucan remodelling in C. deneoformans survival. These findings add new insight about the role of β‐1,3‐glucan in fungal biology and demonstrate the potential of nanobodies in targeting fungal enzymes to combat invasive fungal diseases. [ABSTRACT FROM AUTHOR]

Rising temperature is a major threat to the normal growth and development of maize, resulting in low yield production and quality. The mechanism of maize in response to heat stress remains uncertain. In this study, a maize mutant Zmhsl-1 (heat sensitive leaves) with wilting and curling leaves under high temperatures was identified from maize Zheng 58 (Z58) mutant lines generated by ethyl methanesulfonate (EMS) mutagenesis. The Zmhsl-1 plants were more sensitive to increased temperature than Z58 in the field during growth season. The Zmhsl-1 plants had lower plant height, lower yield, and lower content of photosynthetic pigments. A bulked segregant analysis coupled with whole-genome sequencing (BSA-seq) enabled the identification of the corresponding gene, named ZmHSL, which encodes an endo-β-1,4-xylanase from the GH10 family. The loss-of-function of ZmHSL resulted in reduced lignin content in Zmhsl-1 plants, leading to defects in water transport and more severe leaf wilting with the increase in temperature. RNA-seq analysis revealed that the differentially expressed genes identified between Z58 and Zmhsl-1 plants are mainly related to heat stress-responsive genes and unfolded protein response genes. All these data indicated that ZmHSL plays a key role in lignin synthesis, and its defective mutation causes changes in the cell wall structure and gene expression patterns, which impedes water transport and confers higher sensitivity to high-temperature stress. [ABSTRACT FROM AUTHOR]

SUMMARY Xylan is one of the major hemicelluloses in plant cell walls and its xylosyl backbone is often decorated at O‐2 with glucuronic acid (GlcA) and/or methylglucuronic acid (MeGlcA) residues. The GlcA/MeGlcA side chains may be further substituted with 2‐O‐arabinopyranose (Arap) or 2‐O‐galactopyranose (Gal) residues in some plant species, but the enzymes responsible for these substitutions remain unknown. During our endeavor to investigate the enzymatic activities of Arabidopsis MUR3‐clade members of the GT47 glycosyltransferase family, we found that one of them was able to transfer Arap from UDP‐Arap onto O‐2 of GlcA side chains of xylan, and thus it was named xylan 2‐O‐arabinopyranosyltransferase 1 (AtXAPT1). The function of AtXAPT1 was verified in planta by its T‐DNA knockout mutation showing a loss of the Arap substitution on xylan GlcA side chains. Further biochemical characterization of XAPT close homologs from other plant species demonstrated that while the poplar ones had the same catalytic activity as AtXAPT1, those from Eucalyptus, lemon‐scented gum, sea apple, 'Ohi'a lehua, duckweed and purple yam were capable of catalyzing both 2‐O‐Arap and 2‐O‐Gal substitutions of xylan GlcA side chains albeit with differential activities. Sequential reactions with XAPTs and glucuronoxylan methyltransferase 3 (GXM3) showed that XAPTs acted poorly on MeGlcA side chains, whereas GXM3 could efficiently methylate arabinosylated or galactosylated GlcA side chains of xylan. Furthermore, molecular docking and site‐directed mutagenesis analyses of Eucalyptus XAPT1 revealed critical roles of several amino acid residues at the putative active site in its activity. Together, these findings establish that XAPTs residing in the MUR3 clade of family GT47 are responsible for 2‐O‐arabinopyranosylation and 2‐O‐galactosylation of GlcA side chains of xylan. [ABSTRACT FROM AUTHOR]

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Plant cell walls are largely composed of polysaccharide polymers, including cellulose, hemicelluloses (xyloglucan, xylan, mannan, and mixed-linkage β-1,3/1,4-glucan), and pectins. Among these cell wall polysaccharides, xyloglucan, xylan, mannan, and pectins are often O-acetylated, and polysaccharide O-acetylation plays important roles in cell wall assembly and disease resistance. Genetic and biochemical analyses have implicated the involvement of three groups of proteins in plant cell wall polysaccharide O-acetylation: trichome birefringence-like (TBL)/domain of unknown function 231 (DUF231), reduced wall acetylation (RWA), and altered xyloglucan 9 (AXY9). Although the exact roles of RWAs and AXY9 are yet to be identified, members of the TBL/DUF231 family have been found to be O-acetyltransferases responsible for the O-acetylation of xyloglucan, xylan, mannan, and pectins. Here, we provide a comprehensive overview of the occurrence of O-acetylated cell wall polysaccharides, the biochemical properties, structural features, and evolution of cell wall polysaccharide O-acetyltransferases, and the potential biotechnological applications of manipulations of cell wall polysaccharide acetylation. Further in-depth studies of the biochemical mechanisms of cell wall polysaccharide O-acetylation will not only enrich our understanding of cell wall biology, but also have important implications in engineering plants with increased disease resistance and reduced recalcitrance for biofuel production. [ABSTRACT FROM AUTHOR]

Social Impact Statement Summary Cassava is a vital food source for millions worldwide, crucial for food security and economic stability. This study analyzed cell wall polysaccharides in cassava roots to understand their impact on cooking properties. We found these polysaccharides influence the textural attributes of cassava roots, essential for both cooking and consumption. The research highlights the need to further identify and analyze cassava cell wall components. By improving our understanding of these components, we can improve food security, affordability, and resilience in diverse regions, ultimately contributing to global food security and better aligning with consumer preferences. The textural attributes of cassava roots significantly influence preferences in cooking and consumption as a food source, yet the specific components dictating these properties remain unclear. We aimed to identify the factors shaping the cooking properties of cassava roots. We conducted a compositional analysis of 22 traits in a diverse F1 biparental population derived from soft‐ and hard‐boiling progenitors. The traits encompassed cooking qualities, starch properties, and cell wall composition. Specific cell wall components including cellulose, xylan, un‐esterified, and methyl‐esterified homogalacturonan (HG) demonstrated a correlation with cooking quality attributes: sensory assessments related to texture (SAT) and water absorption during boiling (WAB). Correlation and regression analyses revealed that these wall components collectively contribute to 20% of SAT variability and 14% of WAB variability. SAT appeared to be influenced by methyl‐esterified and un‐esterified HGs, xylan, and cellulose, impacting the tensile strength of the cell wall. Conversely, WAB appeared to be associated with methyl‐esterified HG, potentially altering water absorption properties. Although genome‐wide association studies (GWAS) were unable to identify significant SNPs for SAT and WAB, notable associations emerged for cellulose, xylan, and un‐esterified‐ and methyl‐esterified HG. Candidate genes associated with these SNPs point towards diverse cell wall‐related proteins, transcription factors, sugar metabolism‐related genes, and glycosyl hydrolases. This study provides insights into the relationship between cassava root compositions and cooking characteristics and the role of wall components in determining the cooking quality of edible cassava. This information represents a substantial contribution towards the development of protocols for selecting varieties with texture preferences. [ABSTRACT FROM AUTHOR]

Background and Aim: The spread of antibiotic resistance and mineral depletion in soils encourages an intensive search for highly effective and environmentally safe bactericidal agents and sources of macro- and micro-elements. The most profitable solution would combine both the described tasks. Ultrafine particles (UFPs) have this functionality. Thus, this study aimed to analyze the bioluminescence and external morphological changes of Escherichia coli cells after contact with Mn2O3 and Co3O4 UFPs at effective concentrations (ECs). Materials and Methods: The antibiotic properties of the studied samples were determined on a multifunctional microplate analyzer TECAN Infinite F200 (Tecan Austria GmbH, Austria) by fixing the luminescence value of the bacterial strain E. coli K12 TG11 (Ecolum, NVO Immunotech Closed Joint Stock Company, Russia). Morphological changes in the cell structure were evaluated using a Certus Standard EG-5000 atomic force microscope equipped with NSPEC software (Nano Scan Technology LLC, Russia). Results: The obtained results indicate high bactericidal properties of Co3O4 and Mn2O3 UFPs (EC50 at 3.1 x 10-5 and 1.9 x 10-3 mol/L, respectively) due to the degradation of the cell wall, pathological increase in size, disruption of septic processes, and loss of cytoplasmic contents. Conclusion: The prospects for the environmentally safe use of ultrafine materials are outlined. The limits of the dosages of Co3O4 and Mn2O3 UFPs recommended for further study in vitro and in vivo in feeding farm animals are established (no more than 4.9 x 10-4 mol/L for Mn2O3 UFPs and 1.5 x 10-5 mol/L for Co3O4 UFPs). The limitation of the work is the lack of experiments to determine the mechanisms of the toxic effect of UFP on bacteria, protein structures, and DNA and oxidative stress, which is planned to be performed in the future together with in situ and in vivo studies on animals. [ABSTRACT FROM AUTHOR]

Candida albicans is an oral mucosal commensal fungus that transforms into an opportunistic pathogen under specific conditions, including immunosuppression. It causes oral and systemic candidiasis, which results in a significant health burden. Furthermore, an alarming rise in antifungal drug resistance in Candida species raises the urgent need for novel drugs and drug targets. C. albicans Dfg5 and Dcw1 are homologous cell wall alpha-1,6-mannosidases with critical functions and represent potential new drug targets. Our past studies have shown that Dfg5 and Dcw1 function in cell wall biogenesis through the cross-linking of glycoproteins into the cell wall, thus playing a key role in cell wall integrity. Additionally, Dfg5 and Dcw1 are required for hyphal morphogenesis. However, the exact functions of Dfg5 and Dcw1 in cell wall integrity, hyphal morphogenesis, and pathogenesis are not known. In this study, we determined the relation of Dfg5 and Dcw1 with Hog1 MAPK, which plays a key role in cell wall integrity via the regulation of chitin synthesis in C. albicans. Additionally, we also determined the effects of dfg5 and dcw1 mutations on the gene expression of transcriptional regulators of hyphal morphogenesis. Furthermore, we determined the effects of dfg5 and dcw1 mutations on pathogenesis in a mouse model of oral candidiasis. Our results demonstrate that dfg5 and dcw1 mutations, as well as a hog1 knockout mutation, result in the dysregulation of chitin synthesis, resulting in a cell separation defect. Heterozygous and conditional mutations in dfg5 and dcw1 resulted in decreased transcriptional levels of cst20, a positive regulator of hyphal morphogenesis. However, dfg5 and dcw1 mutations resulted in increased levels of all the five negative regulators of hyphal morphogenesis—Tup1, Nrg1, Mig1, Rbf1, and Rfg1. Additionally, Tup1 levels were significantly higher than other negative regulators, indicating that Dfg5 and Dcw1 function in hyphal morphogenesis by repressing Tup1. Finally, dfg5 and dcw1 mutations affected the ability of C. albicans to cause oral candidiasis in mice. Thus, the cell wall glycosidases Dfg5 and Dcw1 are required for virulence and pathogenesis and represent novel drug targets. [ABSTRACT FROM AUTHOR]

The brown midrib bmr6 and bmr12 mutants of sorghum (Sorghum bicolor) have alterations to the phenylpropanoid pathway impairing the activity of cinnamyl alcohol dehydrogenase (CAD) and/or caffeate5/hydroxyferulate O‐methyl transferase (COMT) enzymes, which inhibit lignin synthesis. Interestingly, these phenylpropanoids can also act as sunscreen compounds in plants and potentially attenuate ultraviolet radiation. We examined the effects of ultraviolet‐B (UV‐B; 280–320 nm) exclusion on growth, cell‐wall constituents and UV‐screening abilities of bmr6, bmr12, a double mutant (bmr6 bmr12; dm) and wild‐type (WT) genotypes of S. bicolor. Plants were grown in a UV‐transparent greenhouse under filters that either transmitted 2.8% (Mylar) or 90% (Aclar) of UV‐B. The greenhouse experiment was a 2 × 4 (UV treatment × genotype) complete factorial design. Sorghum grown under reduced UV were 23% taller and had 22% fewer leaves. Among genotypes, the WT plants were 5%–12% taller than the bmr6, bmr12 and dm mutants. The near‐ambient UV‐B treatment group was more effective at UV screening and had a 16% higher UV‐screening effectiveness than those under reduced UV‐B. Sorghum plants with the bmr6 and dm genotypes had 8%–19% higher UV‐shield than the bmr12 and WT. Plants grown under the reduced UV‐B treatment had 5% less hemicellulose and 6% more cellulose in their cell walls. There were no overall treatment effects on bulk soluble phenolics, chlorophyll fluorescence (Fv/Fm) or lignin concentrations. These results are a possible indication that the bmr mutants of S. bicolor have a varied response to UV‐B exclusion due to alterations in the phenylpropanoid pathway leading to redistribution of metabolites. [ABSTRACT FROM AUTHOR]

Enhancing stalk strength is a crucial strategy to reduce lodging. We identified a maize inbred line, QY1, with superior stalk mechanical strength. Comprehensive analyses of the microstructure, cell wall composition, and transcriptome of QY1 were performed to elucidate the underlying factors contributing to its increased strength. Notably, both the vascular bundle area and the thickness of the sclerenchyma cell walls in QY1 were significantly increased. Furthermore, analyses of cell wall components revealed a significant increase in cellulose content and a notable reduction in lignin content. RNA sequencing (RNA-seq) revealed changes in the expression of numerous genes involved in cell wall synthesis and modification, especially those encoding pectin methylesterase (PME). Variations in PME activity and the degree of methylesterification were noted. Additionally, glycolytic efficiency in QY1 was significantly enhanced. These findings indicate that QY1 could be a valuable resource for the development of maize varieties with enhanced stalk mechanical strength and for biofuel production. [ABSTRACT FROM AUTHOR]

Plant seeds and fruits, like those of Ocimum basilicum , develop a mucilaginous envelope rich in pectins and cellulosic fibers upon hydration. This envelope promotes adhesion for attachment to soils and other substrates for dispersal and protection of the seed for a safe germination. Initially at hydration, the mucilage envelope demonstrates low adhesion and friction, but shows increasing adhesive and frictional properties during dehydration. However, the mechanisms underlying the cellulose fiber arrangement and the mechanical properties, especially the elasticity modulus of the mucilage envelope at different hydration conditions are not fully known. In this study, which is based on scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and light microscopy, the structure of the seed coat and arrangement of the cellulose fibers of basil seeds were characterized. Moreover, we performed pull-off force measurements to estimate adhesive properties and JKR-tests to estimate E-modulus of the mucilage at different hydration levels. Microscopy results demonstrate that cellulose fibers are split at their free ends into smaller fibrils, which might enhance the adhesive properties of the mucilage. Adhesive forces in contact increased during dehydration and reached maximum of 33 mN shortly before complete dehydration. The E-modulus of the mucilage changed from 1.4 KPa in water to up to 2.1 MPa in the mucilage at the maximum of its adhesion performance. Obtained results showed hydrogel-like mechanical properties during dehydration and cellulose fiber structures similar to the nanofibrous systems in other organisms with strong adhesive properties. This paper reveals the hierarchical cellulose fiber structure in Ocimum basilicum's mucilaginous seed coat, suggesting increased fiber splitting towards the end, potentially enhancing adhesion contact areas. Mechanical tests explore elasticity modulus and adhesion force during various hydration stages, crucial as these properties evolve with mucilage desiccation. A rare focus on mucilaginous seed coat mechanical properties, particularly cellulose-reinforced fibers, provides insight into the hydrogel-like mucilage of plant seeds. Adhesion forces peak just before complete desiccation and then decline rapidly. As mucilage water content decreases, the E-modulus rises, displaying hydrogel-like properties during early dehydration stages with higher water content. This study might bring the focus to plant seeds as inspiration for biodegradable glues and applications for hydrogel research. [Display omitted] [ABSTRACT FROM AUTHOR]

Phelipanche ramosa is a root parasitic plant fully dependent on host plants for nutrition and development. Upon germination, the parasitic seedling develops inside the infected roots a specific organ, the haustorium, thanks to the cell wall-degrading enzymes of haustorial intrusive cells, and induces modifications in the host's cell walls. The model plant Arabidopsis thaliana is susceptible to P. ramosa; thus, mutants in cell wall metabolism, particularly those involved in pectin remodeling, like Atpme3-1, are of interest in studying the involvement of cell wall-degrading enzymes in the establishment of plant–plant interactions. Host–parasite co-cultures in mini-rhizotron systems revealed that parasite attachments are twice as numerous and tubercle growth is quicker on Atpme3-1 roots than on WT roots. Compared to WT, the increased susceptibility in AtPME3-1 is associated with reduced PME activity in the roots and a lower degree of pectin methylesterification at the host–parasite interface, as detected immunohistochemically in infected roots. In addition, both WT and Atpme3-1 roots responded to infestation by modulating the expression of PAE- and PME-encoding genes, as well as related global enzyme activities in the roots before and after parasite attachment. However, these modulations differed between WT and Atpme3-1, which may contribute to different pectin remodeling in the roots and contrasting susceptibility to P. ramosa. With this integrative study, we aim to define a model of cell wall response to this specific biotic stress and indicate, for the first time, the role of PME3 in this parasitic plant–plant interaction. [ABSTRACT FROM AUTHOR]

BACKGROUND RESULTS CONCLUSION Melatonin, a hormone present in animals and some plants, has garnered attention for its potential in preserving harvested produce. Softening due to changes in cell wall composition and wilting caused by weight loss are the major reasons for the loss of commercial value in postharvest okra. This study aimed to evaluate the impact of melatonin on the softening and weight loss of postharvest okra.The results revealed that the application of melatonin had a significant influence on the maintenance of fruit firmness by inhibiting the breakdown and dissolution of cell wall polysaccharides by suppressing the expression of specific genes responsible for cell wall degradation in okra. Conversely, melatonin treatment positively influenced the expression of genes involved in the synthesis of cell wall components. Furthermore, the treatment exhibited notable benefits in reducing weight loss in okra, which was accomplished by promoting the closure of stomata – the tiny pores on the surface of the fruit.Melatonin could serve as a novel approach to reduce water loss, delay fruit softening and extend the shelf life of okra. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Wheat bran, the main by-product of dry milling of wheat, is currently mainly used in the animal feed industry, but has attracted attention as a food ingredient owing to its high dietary fiber and phytochemical contents, providing excellent physiological effects. The bran layers (aleurone layer, outer pericarp and intermediate layer) contain different compositions, structures, and nutrients, and have different properties. Each layer, when separated and isolated, potentially could find more extensive applications in foods. This triggered interest in isolating the bran layers using milling and wet- or dry-fractionation techniques based on their chemical or physical properties. The recent progress has allowed the production of commercial products from wheat bran layers, particularly aleurone-rich products, enhancing the value of wheat bran layers and their applications in food. The present review highlights the recent advances in studying the chemical composition including distribution of chemical components, physical structure, biopolymer matrix, and physicochemical properties of each wheat bran layer. Technologies to fractionate wheat bran layers and utilization of different bran layers in foods are discussed and reviewed, providing new strategies for improving the value of wheat bran and utilization of wheat bran in foods. [ABSTRACT FROM AUTHOR]

Humus (HS) reservoirs can embed microbial necromass (including cell wall components that are intact or with varying degrees of fragmentation) in small pores, raising widespread concerns about the potential for C/N interception and stability in composting systems. In this study, fresh cow manure and sawdust were used for microbial solid fermentation, and the significance of microbial residues in promoting humification was elucidated by measuring their physicochemical properties and analyzing their microbial informatics. These results showed that the stimulation of external carbon sources (NaHCO3) led to an increase in the accumulation of bacterial necromass C/N from 6.19 and 0.91 µg/mg to 21.57 and 3.20 µg/mg, respectively. Additionally, fungal necromass C/N values were about 3 times higher than the initial values. This contributed to the increase in HS content and the increased condensation of polysaccharides and nitrogen-containing compounds during maturation. The formation of cellular debris mainly depends on the enrichment of Actinobacteria, Proteobacteria, Ascomycota, and Chytridiomycota. Furthermore, Euryarchaeota was the core functional microorganism secreting cell wall lytic enzymes (including AA3, AA7, GH23, and GH15). In conclusion, this study comprehensively analyzed the transformation mechanisms of cellular residuals at different profile scales, providing new insights into C/N cycles and sequestration. [ABSTRACT FROM AUTHOR]

As an essential component of the fungal cell wall, β-1,6-glucan has an important role in the growth and development of fungi, but its distribution has not been investigated in Magnaporthe oryzae. Here, a novel β-1,6-glucanase from M. oryzae, MoGlu16, was cloned and expressed in Pichia pastoris. The enzyme was highly active on pustulan, with a specific activity of 219.0 U/mg at pH 5.0 and 50℃, and showed great selectivity for continuous β-1,6-glycosidic bonding polysaccharides. Based on this, β-1,6-glucan was selectively visualized in the vegetative hyphae, conidia and bud tubes of M. oryzae using a hydrolytically inactive GFP-tagged MoGlu16 with point mutations at the catalytic position (His-MoGlu16E236A-Gfp). The spore germination and appressorium formation were significantly inhibited after incubation of 105/ml conidia with 0.03 μg/μl MoGlu16. Mycelia treated with MoGlu16 produced reactive oxygen species and triggered the cell wall integrity pathway, increasing the expression levels of genes involved in cell wall polysaccharide synthesis. These results revealed that MoGlu16 participated in the remodeling of cell wall in M. oryzae, laying a foundation for the analysis of cell wall structure. [ABSTRACT FROM AUTHOR]

SUMMARY: Cassava, a pivotal tropical crop, exhibits rapid growth and possesses a substantial biomass. Its stem is rich in cellulose and serves as a crucial carbohydrate storage organ. The height and strength of stems restrict the mechanised operation and propagation of cassava. In this study, the triple helix transcription factor MeGT2.6 was identified through yeast one‐hybrid assay using MeCesA1pro as bait, which is critical for cellulose synthesis. Over‐expression and loss‐of‐function lines were generated, and results revealed that MeGT2.6 could promote a significant increase in the plant height, stem diameter, cell size and thickness of SCW of cassava plant. Specifically, MeGT2.6 upregulated the transcription activity of MeGA20ox1 and downregulated the expression level of MeGA2ox1, thereby enhancing the content of active GA3, resulting in a large cell size, high plant height and long stem diameter in cassava. Moreover, MeGT2.6 upregulated the transcription activity of MeCesA1, which promoted the synthesis of cellulose and hemicellulose and produced a thick secondary cell wall. Finally, MeGT2.6 could help supply additional substrates for the synthesis of cellulose and hemicellulose by upregulating the invertase genes (MeNINV1/6). Thus, MeGT2.6 was found to be a multiple regulator; it was involved in GA metabolism and sucrose decomposition and the synthesis of cellulose and hemicellulose. [ABSTRACT FROM AUTHOR]

Summary Polysaccharide structural complexity not only influences cell wall strength and extensibility but also hinders pathogenic and biotechnological attempts to saccharify the wall. In certain species and tissues, glucuronic acid side groups on xylan exhibit arabinopyranose or galactose decorations whose genetic and evolutionary basis is completely unknown, impeding efforts to understand their function and engineer wall digestibility. Genetics and polysaccharide profiling were used to identify the responsible loci in Arabidopsis and Eucalyptus from proposed candidates, while phylogenies uncovered a shared evolutionary origin. GH30‐family endo‐glucuronoxylanase activities were analysed by electrophoresis, and their differing specificities were rationalised by phylogeny and structural analysis. The newly identified xylan arabinopyranosyltransferases comprise an overlooked subfamily in the GT47‐A family of Golgi glycosyltransferases, previously assumed to comprise mainly xyloglucan galactosyltransferases, highlighting an unanticipated adaptation of both donor and acceptor specificities. Further neofunctionalisation has produced a Myrtaceae‐specific xylan galactosyltransferase. Simultaneously, GH30 endo‐glucuronoxylanases have convergently adapted to overcome these decorations, suggesting a role for these structures in defence. The differential expression of glucuronoxylan‐modifying genes across Eucalyptus tissues, however, hints at further functions. Our results demonstrate the rapid adaptability of biosynthetic and degradative carbohydrate‐active enzyme activities, providing insight into plant–pathogen interactions and facilitating plant cell wall biotechnological utilisation. [ABSTRACT FROM AUTHOR]

An Arabidopsis sterol mutant, smt2 smt3, defective in sterolmethyltransferase2 (SMT2), exhibits severe growth abnormalities. The loss of C-24 ethyl sterols, maintaining the biosynthesis of C-24 methyl sterols and brassinosteroids, suggests specific roles of C-24 ethyl sterols. We characterized the subcellular localizations of fluorescent protein-fused sterol biosynthetic enzymes, such as SMT2-GFP, and found these enzymes in the endoplasmic reticulum during interphase and identified their movement to the division plane during cytokinesis. The mobilization of endoplasmic reticulum-localized SMT2-GFP was independent of the polarized transport of cytokinetic vesicles to the division plane. In smt2 smt3, SMT2-GFP moved to the abnormal division plane, and unclear cell plate ends were surrounded by hazy structures from SMT2-GFP fluorescent signals and unincorporated cellulose debris. Unusual cortical microtubule organization and impaired cytoskeletal function accompanied the failure to determine the cortical division site and division plane formation. These results indicated that both endoplasmic reticulum membrane remodeling and cytokinetic vesicle transport during cytokinesis were impaired, resulting in the defects of cell wall generation. The cell wall integrity was compromised in the daughter cells, preventing the correct determination of the subsequent cell division site. We discuss the possible roles of C-24 ethyl sterols in the interaction between the cytoskeletal network and the plasma membrane. [ABSTRACT FROM AUTHOR]

Key message: Hydrogen sulfide improved cold resistance of tomato fruits by regulating energy metabolism and delaying cell wall degradation, thereby alleviating the damage of cold storage on fruits. Postharvest cold storage in tomato fruits extended shelf life but caused the appearance of chilling injury (CI), appeared by softness and spots on the surface of the fruits. These changes were linked closely with energy and cell wall metabolisms. Hydrogen sulfide (H2S), as the gaseous fresh-keeping regulator, was used in the present study to investigate the effects of H2S on energy and cell wall metabolisms in tomato fruits during cold storage. Fruits after harvest were fumigated with different concentrations (0, 0.5, 1, 1.5 mM) of sodium hydrosulfide (NaHS) solution as H2S honor for 24 h and stored at 4 °C for 25 days. The results showed that 1 and 1.5 mM NaHS solution fumigation promoted the accumulation of endogenous H2S, followed by the increase in L-cysteine desulfurase (LCD) and D-cysteine desulfurase (DCD) activities in fruits during cold storage. It was also found that 1 and 1.5 mM NaHS treatments improved H+-ATPase, Ca2+-ATPase, cytochrome C oxidase (CCO), and succinic dehydrogenase (SDH) activities. Moreover, the contents of cellulose and hemicellulose were increased by 1 and 1.5 mM NaHS, following down-regulated activities of cellulase (CL), pectin lyase (PL), α-mannosidase (α-man) and β-Galactosidase (β-Gal) and down-regulated expression of PL1, PL8, MAN4 and MAN7 genes. Thus, H2S alleviates CI led by cold storage in tomato fruits via regulating energy and cell wall metabolisms. [ABSTRACT FROM AUTHOR]

Key message: Calcium polypeptide plays a key role during cadmium stress responses in rice, which is involved in increasing peroxidase activity, modulating pectin methylesterase activity, and regulating cell wall by reducing malondialdehyde content. Cadmium (Cd) contamination threatens agriculture and human health globally, emphasizing the need for sustainable methods to reduce cadmium toxicity in crops. Calcium polypeptide (CaP) is a highly water-soluble small molecular peptide acknowledged for its potential as an organic fertilizer in promoting plant growth. However, it is still unknown whether CaP has effects on mitigating Cd toxicity. Here, we investigated the effect of CaP application on the ability to tolerate toxic Cd in rice. We evaluated the impact of CaP on rice seedlings under varying Cd stress conditions and investigated the effect mechanism of CaP mitigating Cd toxicity by Fourier transform infrared spectroscopy (FTIR), fluorescent probe dye, immunofluorescent labeling, and biochemical analysis. We found a notable alleviation of Cd toxicity by reduced malondialdehyde content and increased peroxidase activity. In addition, our findings reveal that CaP induces structural alterations in the root cell wall by modulating pectin methylesterase activity. Altogether, our results confirm that CaP not only promoted biomass accumulation but also reduced Cd concentration in rice. This study contributes valuable insights to sustainable strategies for addressing Cd contamination in agricultural ecosystems. [ABSTRACT FROM AUTHOR]

Summary: Unicellular organisms are known to exert tight control over their cell size. In the case of diatoms, abundant eukaryotic microalgae, two opposing notions are widely accepted. On the one hand, the rigid silica cell wall that forms inside the parental cell is thought to enforce geometrical reduction of the cell size. On the other hand, numerous exceptions cast doubt on the generality of this model.Here, we monitored clonal cultures of the diatom Stephanopyxis turris for up to 2 yr, recording the sizes of thousands of cells, in order to follow the distribution of cell sizes in the population.Our results show that S. turris cultures above a certain size threshold undergo a gradual size reduction, in accordance with the postulated geometrical driving force. However, once the cell size reaches a lower threshold, it fluctuates around a constant size using the inherent elasticity of cell wall elements.These results reconcile the disparate observations on cell size regulation in diatoms by showing two distinct behaviors, reduction and homeostasis. The geometrical size reduction is the dominant driving force for large cells, but smaller cells have the flexibility to re‐adjust the size of their new cell walls. [ABSTRACT FROM AUTHOR]

Cell wall is involved in plant growth and plays pivotal roles in plant adaptation to environmental stresses. Cell wall remodelling may be crucial to salt adaptation in the euhalophyte Salicornia europaea. However, the mechanism underlying this process is still unclear. Here, full‐length transcriptome indicated cell wall‐related genes were comprehensively regulated under salinity. The morphology and cell wall components in S. europaea shoot were largely modified under salinity. Through the weighted gene co‐expression network analysis, SeXTH2 encoding xyloglucan endotransglucosylase/hydrolases, and two SeLACs encoding laccases were focused. Meanwhile, SeEXPB was focused according to expansin activity and the expression profiling. Function analysis in Arabidopsis validated the functions of these genes in enhancing salt tolerance. SeXTH2 and SeEXPB overexpression led to larger cells and leaves with hemicellulose and pectin content alteration. SeLAC1 and SeLAC2 overexpression led to more xylem vessels, increased secondary cell wall thickness and lignin content. Notably, SeXTH2 transgenic rice exhibited enhanced salt tolerance and higher grain yield. Altogether, these genes may function in the succulence and lignification process in S. europaea. This work throws light on the regulatory mechanism of cell wall remodelling in S. europaea under salinity and provides potential strategies for improving crop salt tolerance and yields. Summary Statement: SeXTH2 and SeEXPB enhance cell size, two SeLACs promote xylem differentiation and increase the secondary cell wall thickness, which contribute to plant salt tolerance. [ABSTRACT FROM AUTHOR]

SUMMARY: L‐Arabinose (L‐Ara) is a plant‐specific sugar found in cell wall polysaccharides, proteoglycans, glycoproteins, and small glycoconjugates, which play physiologically important roles in cell proliferation and other essential cellular processes. L‐Ara is synthesized as UDP‐L‐arabinose (UDP‐L‐Ara) from UDP‐xylose (UDP‐Xyl) by UDP‐Xyl 4‐epimerases (UXEs), a type of de novo synthesis of L‐Ara unique to plants. In Arabidopsis, the Golgi‐localized UXE AtMUR4 is the main contributor to UDP‐L‐Ara synthesis. However, cytosolic bifunctional UDP‐glucose 4‐epimerases (UGEs) with UXE activity, AtUGE1, and AtUGE3 also catalyze this reaction. For the present study, we first examined the physiological importance of bifunctional UGEs in Arabidopsis. The uge1 and uge3 mutants enhanced the dwarf phenotype of mur4 and further reduced the L‐Ara content in cell walls, suggesting that bifunctional UGEs contribute to UDP‐L‐Ara synthesis. Through the introduction of point mutations exchanging corresponding amino acid residues between AtUGE1 with high UXE activity and AtUGE2 with low UXE activity, two mutations that increase relative UXE activity of AtUGE2 were identified. The crystal structures of AtUGE2 in complex forms with NAD+ and NAD+/UDP revealed that the UDP‐binding domain of AtUGE2 has a more closed conformation and smaller sugar‐binding site than bacterial and mammalian UGEs, suggesting that plant UGEs have the appropriate size and shape for binding UDP‐Xyl and UDP‐L‐Ara to exhibit UXE activity. The presented results suggest that the capacity for cytosolic synthesis of UDP‐L‐Ara was acquired by the small sugar‐binding site and several mutations of UGEs, enabling diversified utilization of L‐Ara in seed plants. [ABSTRACT FROM AUTHOR]

SUMMARY: Poor management and excess fertilization of apple (Malus domestica Borkh.) orchards are causing increasingly serious soil acidification, resulting in Al toxicity and direct poisoning of roots. Strigolactones (SLs) are reported to be involved in plant responses to abiotic stress, but their role and mechanism under AlCl3 stress remain unknown. Here, we found that applying 1 μm GR24 (an SL analoge) significantly alleviated AlCl3 stress of M26 apple rootstock, mainly by blocking the movement of Al through cell wall and by vacuolar compartmentalization of Al. RNA‐seq analysis identified the core transcription factor gene MdWRKY53, and overexpressing MdWRKY53 enhanced AlCl3 tolerance in transgenic apple plants through the same mechanism as GR24. Subsequently, we identified MdPMEI45 (encoding pectin methylesterase inhibitor) and MdALS3 (encoding an Al transporter) as downstream target genes of MdWRKY53 using chromatin immunoprecipitation followed by sequencing (ChIP‐seq). GR24 enhanced the interaction between MdWRKY53 and the transcription factor MdTCP15, further increasing the binding of MdWRKY53 to the MdPMEI45 promoter and inducing MdPMEI45 expression to prevent Al from crossing cell wall. MdWRKY53 also bound to the promoter of MdALS3 and enhanced its transcription to compartmentalize Al in vacuoles under AlCl3 stress. We therefore identified two modules involved in alleviating AlCl3 stress in woody plant apple: the SL‐WRKY+TCP‐PMEI module required for excluding external Al by blocking the entry of Al3+ into cells and the SL‐WRKY‐ALS module allowing internal detoxification of Al through vacuolar compartmentalization. These findings lay a foundation for the practical application of SLs in agriculture. Significance Statement: We identified two modules involved in alleviating AlCl3 stress in woody plant apple: the SL‐WRKY+TCP‐PMEI module required for excluding external Al by blocking the entry of Al3+ into cells and the SL‐WRKY‐ALS module allowing internal detoxification of Al through vacuolar compartmentalization. [ABSTRACT FROM AUTHOR]

Cell wall polysaccharides (dietary fiber) in cereal grains contribute to health benefits. The novelty of the current study was an effort to explore the in vivo therapeutic potential of different cereal bran cell walls against hypercholesterolemia. For this purpose, the cell walls were isolated from different cereal brans (wheat, maize, oats, and barley), and the intake of these cereal bran cell walls was evaluated for their anti‐lipidemic activity in normal and hypercholesterolemic rats. The serum taken from the rats was tested for cholesterol, lipid, and triglyceride profiles before and after treatment. The outcomes of the current study have shown that the cereal cell wall has a significant hypercholesterolemia effect. The biochemical parameters of the control animals were within the normal clinical ranges, indicating that the experimental diets were safe. Among cereal bran cell walls, barley bran significantly decreased cholesterol (56.35 ± 1.35 mg/dL), low‐density lipoprotein (56.35 ± 1.05 mg/dL), triglycerides (105.29 ± 1.95 mg/dL), and increased high‐density lipoprotein level (48.35 ± 1.35 mg/dL). These findings provide conclusive evidence that the cereal cell wall is beneficial in the treatment of hypercholesterolemia and may potentially provide protection against other acute, recurring, or chronic illnesses. [ABSTRACT FROM AUTHOR]

The seed habit is the most complex and successful method of sexual reproduction in vascular plants. It represents a remarkable moment in the evolution of plants that afterward spread on land. In particular, seed size had a pivotal role in evolutionary success and agronomic traits, especially in the field of crop domestication. Given that crop seeds constitute one of the primary products for consumption, it follows that seed size represents a fundamental determinant of crop yield. This adaptative feature is strictly controlled by genetic traits from both maternal and zygotic tissues, although seed development and growth are also affected by environmental cues. Despite being a highly exploited topic for both basic and applied research, there are still many issues to be elucidated for developmental biology as well as for agronomic science. This review addresses a number of open questions related to cues that influence seed growth and size and how they influence seed germination. Moreover, new insights on the genetic–molecular control of this adaptive trait are presented. [ABSTRACT FROM AUTHOR]

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Plant lignocellulosic biomass, i.e. secondary cell walls of plants, is a vital alternative source for bioenergy. However, the acetylation of xylan in secondary cell walls impedes the conversion of biomass to biofuels. Previous studies have shown that REDUCED WALL ACETYLATION (RWA) proteins are directly involved in the acetylation of xylan but the regulatory mechanism of RWAs is not fully understood. In this study, we demonstrate that overexpression of a Populus trichocarpa PtRWA-C gene increases the level of xylan acetylation and increases the lignin content and S/G ratio, ultimately yielding poplar woody biomass with reduced saccharification efficiency. Furthermore, through gene coexpression network and expression quantitative trait loci (eQTL) analysis, we found that PtRWA-C was regulated not only by the secondary cell wall hierarchical regulatory network but also by an AP2 family transcription factor HARDY (HRD). Specifically, HRD activates PtRWA-C expression by directly binding to the PtRWA-C promoter, which is also the cis-eQTL for PtRWA-C. Taken together, our findings provide insights into the functional roles of PtRWA-C in xylan acetylation and consequently saccharification and shed light on synthetic biology approaches to manipulate this gene and alter cell wall properties. These findings have substantial implications for genetic engineering of woody species, which could be used as a sustainable source of biofuels, valuable biochemicals, and biomaterials.

Imaging infections in patients is challenging using conventional methods, motivating the development of positron emission tomography (PET) radiotracers targeting bacteria-specific metabolic pathways. Numerous techniques have focused on the bacterial cell wall, although peptidoglycan-targeted PET tracers have been generally limited to the short-lived carbon-11 radioisotope (t1/2 = 20.4 min). In this article, we developed and tested new tools for infection imaging using an amino sugar component of peptidoglycan, namely, derivatives of N-acetyl muramic acid (NAM) labeled with the longer-lived fluorine-18 (t1/2 = 109.6 min) radioisotope. Muramic acid was reacted directly with 4-nitrophenyl 2-[18F]fluoropropionate ([18F]NFP) to afford the enantiomeric NAM derivatives (S)-[18F]FMA and (R)-[18F]FMA. Both diastereomers were easily isolated and showed robust accumulation by human pathogens in vitro and in vivo, including Staphylococcus aureus. These results form the basis for future clinical studies using fluorine-18-labeled NAM-derived PET radiotracers.

Abstract Cadmium (Cd) is a biologically non-essential heavy metal, a major soil pollutant, and extremely harmful to plants. The phytohormone methyl jasmonate (MeJA) plays an important role in plant heavy-metal resistance. However, the understanding of the effects of MeJA supply level on alleviating Cd toxicity in plants is limited. Here, we investigated how MeJA regulated the development of physiological processes and cell wall modification in Cosmos bipinnatus. We found that low concentrations of MeJA increased the dry weight of seedlings under 120 µM Cd stress by reducing the transport of Cd from roots to shoots. Moreover, a threshold concentration of exogenous MeJA increased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in plant roots, the concentration of Cd in the root cell wall, and the contents of pectin and hemicellulose 1 polysaccharides, through converting Cd into pectin-bound forms. These results suggested that MeJA mitigated Cd toxicity by modulating root cell wall polysaccharide and functional group composition, especially through pectin polysaccharides binding to Cd, with effects on Cd transport capacity, specific chemical forms of Cd, and homeostatic antioxidant systems in C. bipinnatus.