Electron sources for plasma electronics and different technological application

There are the following advantages of applying electron guns with plasma cathodes in devices exciting microwave radiation: stability of their parameters, high density of current, relative insensitivity to ion bombardment and the possibility of operating over a wide range of pressure values of a plasma-generating gas [1-5]. The given work aims at constructing the guns with the parameters necessary for the excitation of microwaves of high amplitudes in the slow-wave structures: the beam energy is 20-30 kV, the current is up to 5 A, and the pulse duration is 0,11÷1 ms. The principal problem arising during construction of heavy-current electron sources with plasma emitters consists in the following: it is necessary to provide such conditions of the gas volume, under which the discharge firing would be stable and the emissive plasma generation be effective, whereas a gas breakdown in the accelerating gap must be eliminated

O-glycosylation in plant and mammal cells: the use of chemical inhibitors to understand the biosynthesis and function of O-glycosylated proteins

Glycosylation is the most common posttranslational modification of proteins and consists of the addition of sugar moiety to proteins. The resulting glycosylated proteins are often secreted to the extracellular compartment or integrated into different cell organelles. This modification was identified in plant as well as in mammalian cells.  A number of plant and mammal proteins are either N- or O-glycosylated. This review focuses on O-glycosylation which refers to linkage of a glycan to hydroxyl group of serine, threonine or proline residues. O-glycosylation can be altered by the action of chemical inhibitors. For instance, 3,4-dehydro-L-proline, ethyl 3,4-dehydroxy benzoate and a,a-dipyridyl inhibit the activity of prolyl4-hydroxylase, a key enzyme for plant O-glycosylation. In addition, a small molecule inhibitor designated 1-68A inhibits the polypeptide N-acetylgalactosaminyltransferases of mammalian cells. The aim of this review is to summarize the role and mechanism of action of these inhibitors of O-glycosylation and their impact on cell development in plants and mammals

Reduced susceptibility to Fusarium head blight in Brachypodium distachyon through priming with the Fusarium mycotoxin deoxynivalenol

Summary: The fungal cereal pathogen Fusarium graminearum produces deoxynivalenol (DON) during infection. The mycotoxin DON is associated with Fusarium head blight (FHB), a disease that can cause vast grain losses. Whilst investigating the suitability of Brachypodium distachyon as a model for spreading resistance to F.graminearum, we unexpectedly discovered that DON pretreatment of spikelets could reduce susceptibility to FHB in this model grass. We started to analyse the cell wall changes in spikelets after infection with F.graminearum wild-type and defined mutants: the DON-deficient Δtri5 mutant and the DON-producing lipase disruption mutant Δfgl1, both infecting only directly inoculated florets, and the mitogen-activated protein (MAP) kinase disruption mutant Δgpmk1, with strongly decreased virulence but intact DON production. At 14 days post-inoculation, the glucose amounts in the non-cellulosic cell wall fraction were only increased in spikelets infected with the DON-producing strains wild-type, Δfgl1 and Δgpmk1. Hence, we tested for DON-induced cell wall changes in B.distachyon, which were most prominent at DON concentrations ranging from 1 to 100ppb. To test the involvement of DON in defence priming, we pretreated spikelets with DON at a concentration of 1ppm prior to F.graminearum wild-type infection, which significantly reduced FHB disease symptoms. The analysis of cell wall composition and plant defence-related gene expression after DON pretreatment and fungal infection suggested that DON-induced priming of the spikelet tissue contributed to the reduced susceptibility to FHB

Dynamic Changes in Arabinogalactan-Protein, Pectin, Xyloglucan and Xylan Composition o the Cell Wall During Microspore Embryogenesis in Brassica napus

[EN] Microspore embryogenesis is a manifestation of plant cell totipotency whereby new cell walls are formed as a consequence of the embryogenic switch. In particular, the callose-rich subintinal layer created immediately upon induction of embryogenesis was recently related to protection against stress. However, little is currently known about the functional significance of other compositional changes undergone by the walls of embryogenic microspores. We characterized these changes in Brassica napus at different stages during induction of embryogenic microspores and development of microspore-derived embryos (MDEs) by using a series of monoclonal antibodies specific for cell wall components, including arabinogalactan-proteins (AGPs), pectins, xyloglucan and xylan. We used JIM13, JIM8, JIM14 and JIM16 for AGPs, CCRC-M13, LM5, LM6, JIM7, JIM5 and LM7 for pectins, CCRC-M1 and LM15 for xyloglucan, and LM11 for xylan. By transmission electron microscopy and quantification of immunogold labeling on high-pressure frozen, freeze-substituted samples, we profiled the changes in cell wall ultrastructure and composition at the different stages of microspore embryogenesis. As a reference to compare with, we also studied in vivo microspores and maturing pollen grains. We showed that the cell wall of embryogenic microspores is a highly dynamic structure whose architecture, arrangement and composition changes dramatically as microspores undergo embryogenesis and then transform into MDEs. Upon induction, the composition of the preexisting microspore intine walls is remodeled, and unusual walls with a unique structure and composition are formed. Changes in AGP composition were related to developmental fate. In particular, AGPs containing the JIM13 epitope were massively excreted into the cell apoplast, and appeared associated to cell totipotency. According to the ultrastructure and the pectin and xyloglucan composition of these walls, we deduced that commitment to embryogenesis induces the formation of fragile, plastic and deformable cell walls, which allow for cell expansion and microspore growth. We also showed that these special walls are transient, since cell wall composition in microspore-derived embryos was completely different. Thus, once adopted the embryogenic developmental pathway and far from the effects of heat shock exposure, cell wall biosynthesis would approach the structure, composition and properties of conventional cell walls.This work was supported by grant AGL2017-88135-R to JS-S from Spanish MINECO jointly funded by FEDER. AD would like to thank the University of Rouen and Normandie Regional Council (France) for financial support.Corral Martínez, P.; Driouich, A.; Seguí-Simarro, JM. (2019). Dynamic Changes in Arabinogalactan-Protein, Pectin, Xyloglucan and Xylan Composition o the Cell Wall During Microspore Embryogenesis in Brassica napus. Frontiers in Plant Science. 10:1-17. https://doi.org/10.3389/fpls.2019.00332S11710Barany, I., Fadon, B., Risueno, M. C., & Testillano, P. S. (2010). Cell wall components and pectin esterification levels as markers of proliferation and differentiation events during pollen development and pollen embryogenesis in Capsicum annuum L. Journal of Experimental Botany, 61(4), 1159-1175. doi:10.1093/jxb/erp392Daher, F. B., & Braybrook, S. A. (2015). How to let go: pectin and plant cell adhesion. Frontiers in Plant Science, 6. doi:10.3389/fpls.2015.00523Cavalier, D. M., Lerouxel, O., Neumetzler, L., Yamauchi, K., Reinecke, A., Freshour, G., … Keegstra, K. (2008). Disrupting Two Arabidopsis thaliana Xylosyltransferase Genes Results in Plants Deficient in Xyloglucan, a Major Primary Cell Wall Component. The Plant Cell, 20(6), 1519-1537. doi:10.1105/tpc.108.059873Chapman, A., Blervacq, A.-S., Hendriks, T., Slomianny, C., Vasseur, J., & Hilbert, J.-L. (2000). Cell wall differentiation during early somatic embryogenesis in plants. II. Ultrastructural study and pectin immunolocalization on chicory embryos. Canadian Journal of Botany, 78(6), 824-831. doi:10.1139/b00-060Cheung, A. Y., & Wu, H.-M. (1999). Arabinogalactan proteins in plant sexual reproduction. Protoplasma, 208(1-4), 87-98. doi:10.1007/bf01279078Corral-Martínez, P., García-Fortea, E., Bernard, S., Driouich, A., & Seguí-Simarro, J. M. (2016). Ultrastructural Immunolocalization of Arabinogalactan Protein, Pectin and Hemicellulose Epitopes Through Anther Development inBrassica napus. Plant and Cell Physiology, 57(10), 2161-2174. doi:10.1093/pcp/pcw133Corral-Martínez, P., Nuez, F., & Seguí-Simarro, J. M. (2010). Genetic, quantitative and microscopic evidence for fusion of haploid nuclei and growth of somatic calli in cultured ms10 35 tomato anthers. Euphytica, 178(2), 215-228. doi:10.1007/s10681-010-0303-zCorral-Martínez, P., & Seguí-Simarro, J. M. (2013). Refining the method for eggplant microspore culture: effect of abscisic acid, epibrassinolide, polyethylene glycol, naphthaleneacetic acid, 6-benzylaminopurine and arabinogalactan proteins. Euphytica, 195(3), 369-382. doi:10.1007/s10681-013-1001-4Cosgrove, D. J. (1997). ASSEMBLY AND ENLARGEMENT OF THE PRIMARY CELL WALL IN PLANTS. Annual Review of Cell and Developmental Biology, 13(1), 171-201. doi:10.1146/annurev.cellbio.13.1.171Cosgrove, D. J. (2005). Growth of the plant cell wall. Nature Reviews Molecular Cell Biology, 6(11), 850-861. doi:10.1038/nrm1746Custers, J. B. M. (2003). Microspore culture in rapeseed (Brassica napus L.). Doubled Haploid Production in Crop Plants, 185-193. doi:10.1007/978-94-017-1293-4_29P. Darley, C., M. Forrester, A., & J. McQueen-Mason, S. (2001). Plant Molecular Biology, 47(1/2), 179-195. doi:10.1023/a:1010687600670Duchow, S., Dahlke, R. I., Geske, T., Blaschek, W., & Classen, B. (2016). Arabinogalactan-proteins stimulate somatic embryogenesis and plant propagation of Pelargonium sidoides. Carbohydrate Polymers, 152, 149-155. doi:10.1016/j.carbpol.2016.07.015El-Tantawy, A.-A., Solís, M.-T., Da Costa, M. L., Coimbra, S., Risueño, M.-C., & Testillano, P. S. (2013). Arabinogalactan protein profiles and distribution patterns during microspore embryogenesis and pollen development in Brassica napus. Plant Reproduction, 26(3), 231-243. doi:10.1007/s00497-013-0217-8Jones, L., Seymour, G. B., & Knox, J. P. (1997). Localization of Pectic Galactan in Tomato Cell Walls Using a Monoclonal Antibody Specific to (1[->]4)-[beta]-D-Galactan. Plant Physiology, 113(4), 1405-1412. doi:10.1104/pp.113.4.1405Kikuchi, A., Satoh, S., Nakamura, N., & Fujii, T. (1995). Differences in pectic polysaccharides between carrot embryogenic and non-embryogenic calli. Plant Cell Reports, 14(5). doi:10.1007/bf00232028Knox, J. P., Linstead, P., King, J., Cooper, C., & Roberts, K. (1990). Pectin esterification is spatially regulated both within cell walls and between developing tissues of root apices. Planta, 181(4). doi:10.1007/bf00193004Knox, J. ., Linstead, P. ., Cooper, J. P. C., & Roberts, K. (1991). Developmentally regulated epitopes of cell surface arabinogalactan proteins and their relation to root tissue pattern formation. The Plant Journal, 1(3), 317-326. doi:10.1046/j.1365-313x.1991.t01-9-00999.xLamport, D. T. A., & Várnai, P. (2012). Periplasmic arabinogalactan glycoproteins act as a calcium capacitor that regulates plant growth and development. New Phytologist, 197(1), 58-64. doi:10.1111/nph.12005Letarte, J., Simion, E., Miner, M., & Kasha, K. J. (2005). Arabinogalactans and arabinogalactan-proteins induce embryogenesis in wheat (Triticum aestivum L.) microspore culture. Plant Cell Reports, 24(12), 691-698. doi:10.1007/s00299-005-0013-5Majewska-Sawka, A., Münster, A., & Wisniewska, E. (2004). Temporal and Spatial Distribution of Pectin Epitopes in Differentiating Anthers and Microspores of Fertile and Sterile Sugar Beet. Plant and Cell Physiology, 45(5), 560-572. doi:10.1093/pcp/pch066Makowska, K., Kałużniak, M., Oleszczuk, S., Zimny, J., Czaplicki, A., & Konieczny, R. (2017). Arabinogalactan proteins improve plant regeneration in barley (Hordeum vulgare L.) anther culture. Plant Cell, Tissue and Organ Culture (PCTOC), 131(2), 247-257. doi:10.1007/s11240-017-1280-xMarcus, S. E., Verhertbruggen, Y., Hervé, C., Ordaz-Ortiz, J. J., Farkas, V., Pedersen, H. L., … Knox, J. P. (2008). Pectic homogalacturonan masks abundant sets of xyloglucan epitopes in plant cell walls. BMC Plant Biology, 8(1), 60. doi:10.1186/1471-2229-8-60McCartney, L., Marcus, S. E., & Knox, J. P. (2005). Monoclonal Antibodies to Plant Cell Wall Xylans and Arabinoxylans. Journal of Histochemistry & Cytochemistry, 53(4), 543-546. doi:10.1369/jhc.4b6578.2005McCartney, L., Ormerod, andrew P., Gidley, M. J., & Knox, J. P. (2000). Temporal and spatial regulation of pectic (14)-beta-D-galactan in cell walls of developing pea cotyledons: implications for mechanical properties. The Plant Journal, 22(2), 105-113. doi:10.1046/j.1365-313x.2000.00719.xMcCartney, L., Steele-King, C. G., Jordan, E., & Knox, J. P. (2003). Cell wall pectic (1→4)-β-d-galactan marks the acceleration of cell elongation in theArabidopsisseedling root meristem. The Plant Journal, 33(3), 447-454. doi:10.1046/j.1365-313x.2003.01640.xMicheli, F. (2001). Pectin methylesterases: cell wall enzymes with important roles in plant physiology. Trends in Plant Science, 6(9), 414-419. doi:10.1016/s1360-1385(01)02045-3MOHNEN, D. (2008). Pectin structure and biosynthesis. Current Opinion in Plant Biology, 11(3), 266-277. doi:10.1016/j.pbi.2008.03.006Nguema-Ona, E., Vicré-Gibouin, M., Gotté, M., Plancot, B., Lerouge, P., Bardor, M., & Driouich, A. (2014). Cell wall O-glycoproteins and N-glycoproteins: aspects of biosynthesis and function. Frontiers in Plant Science, 5. doi:10.3389/fpls.2014.00499Nothnagel, E. A. (1997). Proteoglycans and Related Components in Plant Cells. International Review of Cytology, 195-291. doi:10.1016/s0074-7696(08)62118-xPaire, A., Devaux, P., Lafitte, C., Dumas, C., & Matthys-Rochon, E. (2003). Plant Cell, Tissue and Organ Culture, 73(2), 167-176. doi:10.1023/a:1022805623167Pattathil, S., Avci, U., Baldwin, D., Swennes, A. G., McGill, J. A., Popper, Z., … Hahn, M. G. (2010). A Comprehensive Toolkit of Plant Cell Wall Glycan-Directed Monoclonal Antibodies. Plant Physiology, 153(2), 514-525. doi:10.1104/pp.109.151985Peña, M. J., Ryden, P., Madson, M., Smith, A. C., & Carpita, N. C. (2004). The Galactose Residues of Xyloglucan Are Essential to Maintain Mechanical Strength of the Primary Cell Walls in Arabidopsis during Growth. Plant Physiology, 134(1), 443-451. doi:10.1104/pp.103.027508Pennell, R. I., Janniche, L., Kjellbom, P., Scofield, G. N., Peart, J. M., & Roberts, K. (1991). Developmental Regulation of a Plasma Membrane Arabinogalactan Protein Epitope in Oilseed Rape Flowers. The Plant Cell, 1317-1326. doi:10.1105/tpc.3.12.1317Pereira, A. M., Pereira, L. G., & Coimbra, S. (2015). Arabinogalactan proteins: rising attention from plant biologists. Plant Reproduction, 28(1), 1-15. doi:10.1007/s00497-015-0254-6Pereira-Netto, A. B., Pettolino, F., Cruz-Silva, C. T. A., Simas, F. F., Bacic, A., Carneiro-Leão, A. M. dos A., … Maurer, J. B. B. (2007). Cashew-nut tree exudate gum: Identification of an arabinogalactan-protein as a constituent of the gum and use on the stimulation of somatic embryogenesis. Plant Science, 173(4), 468-477. doi:10.1016/j.plantsci.2007.07.008Qin, Y., & Zhao, J. (2007). Localization of arabinogalactan-proteins in different stages of embryos and their role in cotyledon formation of Nicotiana tabacum L. Sexual Plant Reproduction, 20(4), 213-224. doi:10.1007/s00497-007-0058-4Rivas-Sendra, A., Corral-Martínez, P., Porcel, R., Camacho-Fernández, C., Calabuig-Serna, A., & Seguí-Simarro, J. M. (2019). Embryogenic competence of microspores is associated with their ability to form a callosic, osmoprotective subintinal layer. Journal of Experimental Botany, 70(4), 1267-1281. doi:10.1093/jxb/ery458Seguí-Simarro, J. M. (2015). High-Pressure Freezing and Freeze Substitution of In Vivo and In Vitro Cultured Plant Samples. Plant Microtechniques and Protocols, 117-134. doi:10.1007/978-3-319-19944-3_7Seguí-Simarro, J. M., & Nuez, F. (2008). Pathways to doubled haploidy: chromosome doubling during androgenesis. Cytogenetic and Genome Research, 120(3-4), 358-369. doi:10.1159/000121085Shu, H., Xu, L., Li, Z., Li, J., Jin, Z., & Chang, S. (2014). Tobacco Arabinogalactan Protein NtEPc Can Promote Banana (Musa AAA) Somatic Embryogenesis. Applied Biochemistry and Biotechnology, 174(8), 2818-2826. doi:10.1007/s12010-014-1228-0Simmonds, D. H., & Keller, W. A. (1999). Significance of preprophase bands of microtubules in the induction of microspore embryogenesis of Brassica napus. Planta, 208(3), 383-391. doi:10.1007/s004250050573Supena, E. D. J., Winarto, B., Riksen, T., Dubas, E., van Lammeren, A., Offringa, R., … Custers, J. (2008). Regeneration of zygotic-like microspore-derived embryos suggests an important role for the suspensor in early embryo patterning. Journal of Experimental Botany, 59(4), 803-814. doi:10.1093/jxb/erm358Tang, X.-C. (2006). The role of arabinogalactan proteins binding to Yariv reagents in the initiation, cell developmental fate, and maintenance of microspore embryogenesis in Brassica napus L. cv. Topas. Journal of Experimental Botany, 57(11), 2639-2650. doi:10.1093/jxb/erl027Willats, W. G. T., Steele-King, C. G., Marcus, S. E., & Knox, J. P. (1999). Side chains of pectic polysaccharides are regulated in relation to cell proliferation and cell differentiation. The Plant Journal, 20(6), 619-628. doi:10.1046/j.1365-313x.1999.00629.xWillats, W. G. T., Limberg, G., Buchholt, H. C., van Alebeek, G.-J., Benen, J., Christensen, T. M. I. E., … Knox, J. P. (2000). Analysis of pectic epitopes recognised by hybridoma and phage display monoclonal antibodies using defined oligosaccharides, polysaccharides, and enzymatic degradation. Carbohydrate Research, 327(3), 309-320. doi:10.1016/s0008-6215(00)00039-

Toxic metal(loid) speciation during weathering of iron sulfide mine tailings under semi-arid climate

Toxic metalliferous mine-tailings pose a significant health risk to ecosystems and neighboring communities from wind and water dispersion of particulates containing high concentrations of toxic metal(loid)s (e.g., Pb, As, Zn). Tailings are particularly vulnerable to erosion before vegetative cover can be reestablished, i.e., decades or longer in semi-arid environments without intervention. Metal(loid) speciation, linked directly to bioaccessibility and lability, is controlled by mineral weathering and is a key consideration when assessing human and environmental health risks associated with mine sites. At the semi-arid Iron King Mine and Humboldt Smelter Superfund site in central Arizona, the mineral assemblage of the top 2 m of tailings has been previously characterized. A distinct redox gradient was observed in the top 0.5 m of the tailings and the mineral assemblage indicates progressive transformation of ferrous iron sulfides to ferrihydrite and gypsum, which, in turn weather to form schwertmannite and then jarosite accompanied by a progressive decrease in pH (7.3 to 2.3). Within the geochemical context of this reaction front, we examined enriched toxic metal(loid)s As, Pb, and Zn with surficial concentrations 41.1, 10.7, 39.3 mM kg-1 (3080, 2200, and 2570 mg kg-1), respectively. The highest bulk concentrations of As and Zn occur at the redox boundary representing a 1.7 and 4.2 fold enrichment relative to surficial concentrations, respectively, indicating the translocation of toxic elements from the gossan zone to either the underlying redox boundary or the surface crust. Metal speciation was also examined as a function of depth using X-ray absorption spectroscopy (XAS). The deepest sample (180 cm) contains sulfides (e.g., pyrite, arsenopyrite, galena, and sphalerite). Samples from the redox transition zone (25-54 cm) contain a mixture of sulfides, carbonates (siderite, ankerite, cerrusite, and smithsonite) and metal(loid)s sorbed to neoformed secondary Fe phases, principally ferrihydrite. In surface samples (0-35 cm), metal(loid)s are found as sorbed species or incorporated into secondary Fe hydroxysulfate phases, such as schwertmannite and jarosites. Metal-bearing efflorescent salts (e.g., ZnSO4·nH2O) were detected in the surficial sample. Taken together, these data suggest the bioaccessibility and lability of metal(loid)s are altered by mineral weathering, which results in both the downward migration of metal(loid)s to the redox boundary, as well as the precipitation of metal salts at the surface.24 month embargo; published online: 7 February 2015This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

La matrice extracellulaire végétale (rôle dans le contrôle de la morphogenèse cellulaire)

La paroi végétale joue un rôle important durant la morphogenèse cellulaire. Dans ce travail, nous avons étudié le mutant reb1-1 d'arabidopsis qui présente des altérations morphologiques au niveau des racines. La mutation affecte la biosynthèse du galactose et son incorporation dans les polysaccharides complexes de la paroi. En effet, la galactosylation des xyloglucanes est affectée. Par contre, les pectines ne sont pas affectées par la mutation. Ces résultats suggèrent que l'incorporation du galactose dans la paroi serait régulée à l'échelle du polymère. Dans un second temps, une potentielle interaction entre les AGPs et les microtubules corticaux a été étudiée. En utilisant des drogues qui immobilisent les AGPs, nous avons montré que des racines d'Arabidopsis présentaient une altération morphologique et une forte désorganisation des microtubules. Ces résultats suggèrent que les AGPs peuvent influencer les microtubules, et favoriser une interaction physique entre la paroi et le cytosquelette.Plant cell wall plays a key role during cell morphogenesis. Here, we have investigated the occurrence of galactose-containing polysaccharides, in the reb1-1 Arabidopsis mutant roots. The mutation affects galatose biosynthesis. Our data show that mutant roots are devoided by galactosylated xyloglucan side chains. Interestingly, pectin galactosylation is not affected. These findings suggest that galactose biosynthesis and its incorporation into complex polysaccharides is regulated at the polymer level. In the second part of this work, a potential connexion between cell wall arabinogalactan-proteins (AGPs) and microtubules was investigated. AGPs disrupting drugs were used to disturb AGPs dynamic at cell surface. A strong alteration of cell morphology and a rapid cortical microtubules organization were observed. These findings demonstrate that AGPs are able ton influence cortical microtubules, placing them as critical molecular linkers between the cytoskeleton and the plant cell wall.ROUEN-BU Sciences (764512102) / SudocSudocFranceF