Xyloglucan and Its Biosynthesis

The hemicellulosic polysaccharide xyloglucan (XyG), found in the primary cell walls of most plant tissues, is important for structural organization of the cell wall and regulation of growth and development. Significant recent progress in structural characterization of XyGs from different plant species has shed light on the diversification of XyG during plant evolution. Also, identification of XyG biosynthetic enzymes and examination of their interactions suggests the involvement of a multiprotein complex in XyG biosynthesis. This mini-review presents an updated overview of the diversity of XyG structures in plant taxa and recent findings on XyG biosynthesis

Information on the COVID-19 pandemic in daily newspapers' front pages : case study of Spain and Italy

Spain and Italy are amongst the European countries where the COVID-19 pandemic has produced its major impact and where lockdown measures have been the harshest. This research aims at understanding how the corona crisis has been represented in Spanish and Italian media, focusing on reference newspapers. The study analyzes 72 front pages of El País and El Mundo in Spain and Italy's Corriere della Sera and La Repubblica, collecting 710 news items and 3456 data evidences employing a mixed method (both qualitative and quantitative) based on content analysis and hemerographic analysis. Results show a predominance of informative journalistic genres (especially brief and news), while the visual framing emerging from the photographic choice, tend to foster humanization through an emotional representation of the pandemic. Politicians are the most represented actors, showing a high degree of politicization of the crisis

Decreased Polysaccharide Feruloylation Compromises Plant Cell Wall Integrity and Increases Susceptibility to Necrotrophic Fungal Pathogens

The complexity of cell wall composition and structure determines the strength, flexibility, and function of the primary cell wall in plants. However, the contribution of the various components to cell wall integrity (CWI) and function remains unclear. Modifications of cell wall composition can induce plant responses known as CWI control. In this study, we used transgenic expression of the fungal feruloyl esterase AnFAE to examine the effect of post-synthetic modification of Arabidopsis and Brachypodium cell walls. Transgenic Arabidopsis plants expressing AnFAE showed a significant reduction of monomeric ferulic acid, decreased amounts of wall-associated extensins, and increased susceptibility to Botrytis cinerea, compared with wild type. Transgenic Brachypodium showed reductions in monomeric and dimeric ferulic acids and increased susceptibility to Bipolaris sorokiniana. Upon infection, transgenic Arabidopsis and Brachypodium plants also showed increased expression of several defense-related genes compared with wild type. These results demonstrate a role, in both monocot and dicot plants, of polysaccharide feruloylation in plant CWI, which contributes to plant resistance to necrotrophic pathogens. Keywords: ferulic acid, cell wal

Plant root associated chitinases: structures and functions

Chitinases degrade chitin, a linear homopolymer of β-1,4-linked N-acetyl-D-glucosamine (GlcNAc) residues found in the cell walls of fungi and the exoskeletons of arthropods. They are secreted by the roots into the rhizosphere, a complex and dynamic environment where intense nutrient exchange occurs between plants and microbes. Here we modeled, expressed, purified, and characterized Zea mays and Oryza sativa root chitinases, and the chitinase of a symbiotic bacterium, Chitinophaga oryzae 1303 for their activities with chitin, di-, tri-, and tetra-saccharides and Aspergillus niger, with the goal of determining their role(s) in the rhizosphere and better understanding the molecular mechanisms underlying plant-microbe interactions. We show that Zea mays basic endochitinase (ZmChi19A) and Oryza sativa chitinase (OsChi19A) are from the GH19 chitinase family. The Chitinophaga oryzae 1303 chitinase (CspCh18A) belongs to the GH18 family. The three enzymes have similar apparent KM values of (20-40 µM) for the substrate 4-MU-GlcNAc3. They vary in their pH and temperature optima with OsChi19A activity optimal between pH 5–7 and 30–40°C while ZmChi19A and CspCh18A activities were optimal at pH 7-9 and 50–60°C. Modeling and site-directed mutation of ZmChi19A identified the catalytic cleft and the active residues E147 and E169 strategically positioned at ~8.6Å from each other in the folded protein. Cleavage of 4-MU-GlcNAc3 was unaffected by the absence of the CBD but diminished in the absence of the flexible C-terminal domain. However, unlike for the soluble substrate, the CBD and the newly identified flexible C-terminal domain were vital for inhibiting Aspergillus niger growth. The results are consistent with the involvement of the plant chitinases in defense against pathogens like fungi that have chitin exoskeletons. In summary, we have characterized the functional features and structural domains necessary for the activity of two plant root chitinases that are believed to be involved in plant defense and a bacterial chitinase that, along with the plant chitinases, may participate in nutrient recycling in the rhizosphere

Structure of the UV irradiation product of 5-methyl-2-phenyl-1,2,3-diazaphosphole

UV irradiation of 5-methyl-2-phenyl-1,2,3-diazaphosphole leads to 4,4′-didehydro-bis(5-methyl-2-phenyl-1,2,3-diazaphosphole). © 1987 Plenum Publishing Corporation

Reactions of diazaphospholes with isocyanates

A new derivative of a two-coordinated phosphorus atom, and specifically 2-acetyl-4-trichloroacetamido-5-methyl-1,2,3-diazaphosphole, was obtained by the reaction of 2-acetyl-5-methyl-1,2,3-diazaphosphole with trichloroacetyl isocyanate. © 1984 Plenum Publishing Corporation

Reaction of 2-acetyl-3-methoxy-5-methyldiazaphospholine with p-toluenesulfonyl azide

Tosyl azide reacts with 2-acetyl-3-methoxy-5-methyldiazaphospholine to give an iminodiazaphospholine that is stable as a solid, while in solutions, depending on the nature of the solvent and the temperature, it changes to the tautomer with an NH bond and the dimer. The equilibrium interconversion of these three forms was shown on the basis of the IR and31P NMR spectra. © 1982 Plenum Publishing Corporation

Reaction of substituted 5-methyl 1,2,3-diazaphospholes and 1,2,3-diazaarsoles with diphenyldiazomethane and nitrones

1. Reaction of 2-acetyl-5-methyl-1,2,3-diazaphosphole and 5-methyl-2-phenyl-1,2,3-diazaarsole with diphenyldiazomethane leads to formation of phosphirane- and arsirane-containing bicyclic compounds. 2. In reaction with nitrones 5-methyl-2-phenyl-1,2,3-diazaarsole, as well as 2,5-diphenyl-1,2,3-diazaarsole, forms analogous [2+3]-cycloadducts. © 1988 Plenum Publishing Corporation

Influence of RARα gene on MDR1 expression and P-glycoprotein function in human leukemic cells

BACKGROUND: Multidrug resistance (MDR) phenotype of malignant cells is the major problem in the chemotherapy of neoplasia. The treatment of leukemia with retinoids is aimed on the induction of leukemic cells differentiation. However the interconnections between retinoid regulated differentiation of leukemic cells and regulation of MDR remains unclear. METHODS: Four lines of cultured leukemic cells of diverse types of differentiation were infected with RARα gene and stable transfectants were isolated. We investigated the differentiation of these cells as well as the expression of RARα and MDR1 genes and P-glycoprotein (Pgp, MDR protein) functional activity in these cells. RESULTS: All RARα transfected sublines demonstrated the increase in the quantity of RARα mRNA. All these sublines became more differentiated. Intrinsic activity of MDR1 gene (but not Pgp functional activity) was increased in one of the transfectants. All-trans-retinoic acid (ATRA) induced Pgp activity in two of three infectants to a larger extent than in parental cells. CONCLUSION: The data show that RARα regulates MDR1/ Pgp activity in human leukemic cells, in the first place, Pgp activity induced by ATRA. These results show that RARα overexpression in leukemic cells could result in MDR

Polysaccharide Biosynthesis: Glycosyltransferases and Their Complexes

Glycosyltransferases (GTs) are enzymes that catalyze reactions attaching an activated sugar to an acceptor substrate, which may be a polysaccharide, peptide, lipid, or small molecule. In the past decade, notable progress has been made in revealing and cloning genes encoding polysaccharide-synthesizing GTs. However, the vast majority of GTs remain structurally and functionally uncharacterized. The mechanism by which they are organized in the Golgi membrane, where they synthesize complex, highly branched polysaccharide structures with high efficiency and fidelity, is also mostly unknown. This review will focus on current knowledge about plant polysaccharide-synthesizing GTs, specifically focusing on protein-protein interactions and the formation of multiprotein complexes