The rice BRITTLE CULM 4 gene encodes a membrane protein involved in cellulose synthesis in the secondary cell wall.

The formation of secondary cell walls, which provide mechanical strength to the plant body, depends on numerous factors. Studies on rice brittle culm (bc) mutants allow us to identify these factors and gain insights into the mechanisms of secondary cell wall formation. Rice bc4 is a recessive bc mutant with fragile culms and leaves, similar to other bc mutants.

Defective Pollen Meiosis in Arabidopsis Due to Combined Arabinan and Galactan Insufficiency.

The development of pollen is critical for seed plants and depends on precise cellular and molecular mechanisms. It is known that the cell wall plays a key role in the progression of pollen maturation. An earlier phase in pollen development is the meiosis of pollen mother cells (PMCs), a fundamental process for producing viable pollen grains.

Soluble sugars make a greater contribution than cell wall components to the variability of freezing tolerance in wheat cultivars.

Wheat, the second most produced cereal globally, is primarily cultivated in cooler regions. Unexpected freezing temperatures can severely impact wheat production. Wheat and other temperate plants have a cold acclimation mechanism that enhances freezing tolerance, but reduces growth under low, non-freezing temperatures.

Glucomannan engineering highlights roles of galactosyl modification in fine-tuning cellulose-glucomannan interaction in Arabidopsis cell walls.

Widely found in most plant lineages, β-mannans are structurally diverse polysaccharides that can bind to cellulose fibrils to form the complex polysaccharide architecture of the cell wall. How changes in polysaccharide structure influence its cell wall solubility or promote appropriate interaction with cellulose fibrils is poorly understood. Glucomannan backbones acquire variable patterns of galactosyl substitutions, depending on plant developmental stage and species.

SHORT AND CROOKED AWN, encoding the epigenetic regulator EMF1, promotes barley awn development.

The awn is a bristle-like extension from the tip of the lemma in grasses. In barley, the predominant cultivars possess long awns that contribute to grain yield and quality through photosynthesis. In addition, various awn morphological mutants are available in barley, rendering it a useful cereal crop to investigate the mechanims of awn development.

Cytosolic UDP-L-arabinose synthesis by bifunctional UDP-glucose 4-epimerases in Arabidopsis.

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.

Structural changes in cell wall pectic polymers contribute to freezing tolerance induced by cold acclimation in plants.

Subzero temperatures are often lethal to plants. Many temperate herbaceous plants have a cold acclimation mechanism that allows them to sense a drop in temperature and prepare for freezing stress through accumulation of soluble sugars and cryoprotective proteins. As ice formation primarily occurs in the apoplast (the cell wall space), cell wall functional properties are important for plant freezing tolerance.

Smooth Elongation of Pavement Cells Induced by RIC1 Overexpression Leads to Marginal Protrusions of the Cotyledon in Arabidopsis thaliana.

The interdigitated pavement cell shape is suggested to be mechanically rational at both the cellular and tissue levels, but the biological significance of the cell shape is not fully understood. In this study, we explored the potential importance of the jigsaw puzzle-like cell shape for cotyledon morphogenesis in Arabidopsis. We used a transgenic line overexpressing a Rho-like GTPase-interacting protein, ROP-INTERACTIVE CRIB MOTIF-CONTAINING PROTEIN 1 (RIC1), which causes simple elongation of pavement cells.

Integrated genome-wide differentiation and association analyses identify causal genes underlying breeding-selected grain quality traits in japonica rice.

Improving grain quality is a primary objective in contemporary rice breeding. Japanese modern rice breeding has developed two different types of rice, eating and sake-brewing rice, with different grain characteristics, indicating the selection of variant gene alleles during the breeding process. Given the critical importance of promptly and efficiently identifying genes selected in past breeding for future molecular breeding, we conducted genome scans for divergence, genome-wide association studies, and map-based cloning.

Plant type II arabinogalactan: Structural features and modification to increase functionality.

Type II arabinogalactans (AGs) are a highly diverse class of plant polysaccharides generally encountered as the carbohydrate moieties of certain extracellular proteoglycans, the so-called arabinogalactan-proteins (AGPs), which are found on plasma membranes and in cell walls. The basic structure of type II AG is a 1,3-β-D-galactan main chain with 1,6-β-D-galactan side chains. The side chains are further decorated with other sugars such as α-l-arabinose and β-d-glucuronic acid.

Rhamnogalacturonan-I as a nematode chemoattractant from L. super-growing root culture.

Introduction: The soil houses a tremendous amount of micro-organisms, many of which are plant parasites and pathogens by feeding off plant roots for sustenance. Such root pathogens and parasites often rely on plant-secreted signaling molecules in the rhizosphere as host guidance cues. Here we describe the isolation and characterization of a chemoattractant of plant-parasitic root-knot nematodes (, RKN).

Surface-localized glycoproteins act through class C ARFs to fine-tune gametophore initiation in Physcomitrium patens.

Arabinogalactan proteins are functionally diverse cell wall structural glycoproteins that have been implicated in cell wall remodeling, although the mechanistic actions remain elusive. Here, we identify and characterize two AGP glycoproteins, SLEEPING BEAUTY (SB) and SB-like (SBL), that negatively regulate the gametophore bud initiation in Physcomitrium patens by dampening cell wall loosening/softening. Disruption of SB and SBL led to accelerated gametophore formation and altered cell wall compositions.

Temporal cell wall changes during cold acclimation and deacclimation and their potential involvement in freezing tolerance and growth.

Plants adapt to freezing stress through cold acclimation, which is induced by nonfreezing low temperatures and accompanied by growth arrest. A later increase in temperature after cold acclimation leads to rapid loss of freezing tolerance and growth resumption, a process called deacclimation. Appropriate regulation of the trade-off between freezing tolerance and growth is necessary for efficient plant development in a changing environment.

structural modification of type II arabinogalactans with fungal endo-β-1, 6-galactanase in Arabidopsis.

Arabinogalactan-proteins (AGPs) are mysterious extracellular glycoproteins in plants. Although AGPs are highly conserved, their molecular functions remain obscure. The physiological importance of AGPs has been extensively demonstrated with β-Yariv reagent, which specifically binds to AGPs and upon introduction into cells, causes various deleterious effects including growth inhibition and programmed cell death.

Metabolomic analysis of rice brittle culm mutants reveals each mutant- specific metabolic pattern in each organ.

Introduction: Plant cell walls play an important role in providing physical strength and defence against abiotic stress. Rice brittle culm (bc) mutants are a strength-decreased mutant because of abnormal cell walls, and it has been reported that the causative genes of bc mutants affect cell wall composition. However, the metabolic alterations in each organ of bc mutants have remained unknown.

Amino Acids Supplied through the Autophagy/Endocytosis Pathway Promote Starch Synthesis in Protonemal Cells.

The physiological implications of autophagy in plant cells have not been fully elucidated. Therefore, we investigated the consequences of autophagy in the moss Physcomitrella by measuring biochemical parameters (fresh and dry weights; starch, amino acid, carbohydrate, and NH3 content) in wild-type (WT) and autophagy-deficient atg5 Physcomitrella cells. We found higher starch levels and a higher net starch synthesis rate in WT cells than in atg5 cells cultured in a glucose-containing culture medium, whereas net starch degradation was similar in the two strains cultured in a glucose-deficient culture medium.

Hydroxycinnamic acid-modified xylan side chains and their cross-linking products in rice cell walls are reduced in the Xylosyl arabinosyl substitution of xylan 1 mutant.

The intricate architecture of cell walls and the complex cross-linking of their components hinders some industrial and agricultural applications of plant biomass. Xylan is a key structural element of grass cell walls, closely interacting with other cell wall components such as cellulose and lignin. The main branching points of grass xylan, 3-linked l-arabinosyl substitutions, can be modified by ferulic acid (a hydroxycinnamic acid), which cross-links xylan to other xylan chains and lignin.

Superoxide Production by the Red Tide-Producing Complex (Raphidophyceae) Correlates with Toxicity to Aquacultured Fishes.

The marine raphidophyte complex forms red tides, causing heavy mortalities of aquacultured fishes in temperate coastal waters worldwide. The mechanism for fish mortality remains unresolved. Although several toxic chemicals have been proposed as responsible for fish mortality, the cause is still unclear.

Galactoglucomannan structure of Arabidopsis seed-coat mucilage in GDP-mannose synthesis impaired mutants.

Cell-wall polysaccharides are synthesized from nucleotide sugars by glycosyltransferases. However, in what way the level of nucleotide sugars affects the structure of the polysaccharides is not entirely clear. guanosine diphosphate (GDP)-mannose (GDP-Man) is one of the major nucleotide sugars in plants and serves as a substrate in the synthesis of mannan polysaccharides.

Root-knot nematode chemotaxis is positively regulated by l-galactose sidechains of mucilage carbohydrate rhamnogalacturonan-I.

Root-knot nematodes (RKNs) are plant parasites and major agricultural pests. RKNs are thought to locate hosts through chemotaxis by sensing host-secreted chemoattractants; however, the structures and properties of these attractants are not well understood. Here, we describe a previously unknown RKN attractant from flaxseed mucilage that enhances infection of and tomato, which resembles the pectic polysaccharide rhamnogalacturonan-I (RG-I).

Structural features conserved in subclass of type II arabinogalactan.

Arabinogalactan-proteins (AGPs) are extracellular proteoglycans, which are presumed to participate in the regulation of cell shape, thus contributing to the excellent mechanical properties of plants. AGPs consist of a hydroxyproline-rich core-protein and large arabinogalactan (AG) sugar chains, called type II AGs. These AGs have a β-1,3-galactan backbone and β-1,6-galactan side chains, to which other sugars are attached.

Biochemical and structural characterization of a novel 4-O-α-l-rhamnosyl-β-d-glucuronidase from Fusarium oxysporum.

In this study, we have isolated the novel enzyme 4-O-α-l-rhamnosyl-β-d-glucuronidase (FoBGlcA), which releases α-l-rhamnosyl (1→4) glucuronic acid from gum arabic (GA), from Fusarium oxysporum 12S culture supernatant, and for the first time report an enzyme with such catalytic activity. The gene encoding FoBGlcA was cloned and expressed in Pichia pastoris. When GA was subjected to the recombinant enzyme, > 95% of the l-rhamnose (Rha) and d-glucuronic acid in the substrate were released, which indicates that almost all Rha binds to the glucuronic acid at the end of the GA side chains.