Добірка наукової літератури з теми "Cell wall degradation"
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Статті в журналах з теми "Cell wall degradation"
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Singh, Adya P., Yoon Soo Kim, and Ramesh R. Chavan. "Relationship of wood cell wall ultrastructure to bacterial degradation of wood." IAWA Journal 40, no. 4 (November 16, 2019): 845–70. http://dx.doi.org/10.1163/22941932-40190250.
Повний текст джерелаАнотація:
ABSTRACT This review presents information on the relationship of ultrastructure and composition of wood cell walls, in order to understand how wood degrading bacteria utilise cell wall components for their nutrition. A brief outline of the structure and composition of plant cell walls and the degradation patterns associated with bacterial degradation of wood cell walls precedes the description of the relationship of cell wall micro- and ultrastructure to bacterial degradation of the cell wall. The main topics covered are cell wall structure and composition, patterns of cell wall degradation by erosion and tunnelling bacteria, and the relationship of cell wall ultrastructure and composition to wood degradation by erosion and tunnelling bacteria. Finally, pertinent information from select recent studies employing molecular approaches to identify bacteria which can degrade lignin and other wood cell wall components is presented, and prospects for future investigations on wood degrading bacteria are explored.
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Imam, S. H., M. J. Buchanan, H. C. Shin, and W. J. Snell. "The Chlamydomonas cell wall: characterization of the wall framework." Journal of Cell Biology 101, no. 4 (October 1, 1985): 1599–607. http://dx.doi.org/10.1083/jcb.101.4.1599.
Повний текст джерелаАнотація:
The cell wall of the biflagellate alga Chlamydomonas reinhardtii is a multilayered, extracellular matrix composed of carbohydrates and 20-25 polypeptides. To learn more about the forces responsible for the integrity of this cellulose-deficient cell wall, we have begun studies to identify and characterize the framework of the wall and to determine the effects of the cell wall-degrading enzyme, lysin, on framework structure and protein composition. In these studies we used walls released into the medium by mating gametes. When isolated shed walls are degraded by exogenously added lysin, no changes are detected in the charge or molecular weight of the 20-25 wall proteins and glycoproteins when analyzed on one- and two-dimensional polyacrylamide gels, which suggests that degradation of these shed walls is due either to cleavage of peptide bonds very near the ends of polypeptides or that degradation occurs via a mechanism other than proteolysis. Incubation of walls with Sarkosyl-urea solutions removes most of the proteins and yields thin structures that appear to be the frameworks of the walls. Analysis by polyacrylamide gel electrophoresis shows that the frameworks are highly enriched in a polypeptide of Mr 100,000. Treatment of frameworks with lysin leads to their degradation, which indicates that this part of the wall is a substrate for the enzyme. Although lysin converts the Mr 100,000 polypeptide from an insoluble to a soluble form, there is no detectable change in Mr of the framework protein. Solubilization in the absence of lysin requires treatment with SDS and dithiothreitol at 100 degrees C. These results suggest that the Chlamydomonas cell wall is composed of two separate domains: one containing approximately 20 proteins held together by noncovalent interactions and a second domain, containing only a few proteins, which constitutes the framework of the wall. The result that shed walls can be solubilized by boiling in SDS-dithiothreitol indicates that disulfide linkages are critical for wall integrity. Using an alternative method for isolating walls from mechanically disrupted gametes, we have also shown that a wall-shaped portion of these unshed walls is insoluble under the same conditions in which shed walls are soluble. One interpretation of these results is that wall release during mating and the wall degradation that follows may involve distinct biochemical events.
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Mravec, Jozef. "Border cell release: Cell separation without cell wall degradation?" Plant Signaling & Behavior 12, no. 7 (July 3, 2017): e1343778. http://dx.doi.org/10.1080/15592324.2017.1343778.
Повний текст джерела
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Batisse, C., P. J. Coulomb, C. Coulomb, and M. Buret. "Ultrastructure des parois de cerises Bigarreau Burlat de textures différentes au cours de la maturation." Canadian Journal of Botany 74, no. 12 (December 1, 1996): 1974–81. http://dx.doi.org/10.1139/b96-236.
Повний текст джерелаАнотація:
The changes in texture of fruits during ripening are linked to cell wall degradation involving synthesis and degradation of polymers. An increase in pectin solubility leads to cell sliding and an elastic aspect of tissues. The biochemical cell wall process differs between soft and crisp fruits originating from a same cultivar but cultivated under different agroclimatic conditions. Although the proportions of cell wall material are similar, the composition and structure of the two cell walls are very different at maturity. A solubilization of the middle lamella and a restructuration of the primary cell walls arising from the cells separation is observed in crisp fruits. In contrast, the middle lamella of the soft fruits is better preserved and the primary cell walls are thin and show degradation bags delimited by residual membrane formations. In addition, the macroendocytosis process by endosome individualization is more important in soft fruits. In conclusion, the fruit texture depends on the extent of the links between cell wall polymers. Keywords: cherry, cell wall, texture, ultrastructural study.
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Singh, Adya P., Shruti Singh, and Ehsan Bari. "Bacterial Degradation of Wood by Tunnel Formation: Role of TEM in Understanding the Intricate Architecture of Tunnels and the Cell Wall Degradation Process." Microscopy Today 30, no. 5 (September 2022): 24–30. http://dx.doi.org/10.1017/s1551929522001080.
Повний текст джерелаАнотація:
Abstract:Certain bacteria degrade wood by creating tunnels in cell walls. Transmission electron microscopy (TEM) has played a key role in understanding the intricate architecture of the tunnels produced within the cell wall and the process of cell wall degradation. The most prominent feature of tunnels is the presence of periodic crescent-shaped slime bands, which is the single most important diagnostic characteristic of bacterial tunneling-type cell wall degradation. The review presented covers the aspects relevant to understanding bacterial tunneling of wood cell walls, emphasizing the importance of the application of TEM in this area of research.
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Tsuneda, A., and R. G. Thorn. "Interactions of wood decay fungi with other microorganisms, with emphasis on the degradation of cell walls." Canadian Journal of Botany 73, S1 (December 31, 1995): 1325–33. http://dx.doi.org/10.1139/b95-394.
Повний текст джерелаАнотація:
Interactions of two wood decay fungi, Lentinula edodes and Pleurotus ostreatus, with other wood inhabiting microorganisms were investigated on agar and in fagaceous wood, primarily by scanning electron microscopy. Micromorphologically, there were two principal modes of cell wall degradation: (i) selective removal of amorphous wall components, followed by the degradation of skeletal microfibrils, and (ii) simultaneous degradation of all wall components. These two modes were observed in three different degradation systems: (i) sapwood wall degradation by the wood decay fungi, (ii) hyphal wall degradation by mycoparasitic Trichoderma, and (iii) hyphal wall degradation by pathogenic bacteria. The simultaneous-type wall degradation in the systems i and ii was usually caused by hyphal tips. In addition to the three systems, bacteriolysis by the wood decay fungi was also studied. The bacterial cell walls, as well as microfibril bundles of wood cellulose and fungal chitin, were all fragmented into minute granules at later stages of microbial degradation and the granules were further degraded into smaller units. Frequency of occurrence and strength of mycoparasitic activity of Trichoderma harzianum were influenced by the degree of wood decay where the interaction occurred. Presence of both cellulose and chitin microfibrils apparently enhanced the mycoparasitic activity. In Quercus wood, P. ostreatus showed a unidirectional growth toward bacterial colonies, which formed as the result of decomposition of dead nematodes, and consumed the unidentified bacteria. In nitrogen-deficient wood, fungal and bacterial cell walls may serve as an important reservoir of nitrogen for wood inhabiting microorganisms. Key words: wood decay, mycoparasitism, bacteriolysis, cellulose, chitin.
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Murashima, Koichiro, Akihiko Kosugi, and Roy H. Doi. "Synergistic Effects of Cellulosomal Xylanase and Cellulases from Clostridium cellulovorans on Plant Cell Wall Degradation." Journal of Bacteriology 185, no. 5 (March 1, 2003): 1518–24. http://dx.doi.org/10.1128/jb.185.5.1518-1524.2003.
Повний текст джерелаАнотація:
ABSTRACT Plant cell walls are comprised of cellulose and hemicellulose and other polymers that are intertwined, and this complex structure presents a barrier to degradation by pure cellulases or hemicellulases. In this study, we determined the synergistic effects on corn cell wall degradation by the action of cellulosomal xylanase XynA and cellulosomal cellulases from Clostridium cellulovorans. XynA minicellulosomes and cellulase minicellulosomes were found to degrade corn cell walls synergistically but not purified substrates such as xylan and crystalline cellulose. The mixture of XynA and cellulases at a molar ratio of 1:2 showed the highest synergistic effect of 1.6 on corn cell wall degradation. The amounts both of xylooligosaccharides and cellooligosaccharides liberated from corn cell walls were increased by the synergistic action of XynA and cellulases. Although synergistic effects on corn cell wall degradation were found in simultaneous reactions with XynA and cellulases, no synergistic effects were observed in sequential reactions. The possible mechanism of synergism between XynA and cellulases is discussed.
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Campion, C., B. Vian, M. Nicole, and F. Rouxel. "A comparative study of carrot root tissue colonization and cell wall degradation by Pythium violae and Pythium ultimum, two pathogens responsible for cavity spot." Canadian Journal of Microbiology 44, no. 3 (March 1, 1998): 221–30. http://dx.doi.org/10.1139/w97-157.
Повний текст джерелаАнотація:
The process of infection of carrots by Pythium violae and Pythium ultimum, two causes of cavity spot, is described. The first species causes limited root necrosis, the second progressive root rot. Colonization by both species was intracellular and limited within the tissues. Modes of cell wall degradation were studied by staining (PATAg test) and labeling techniques. Pectins were labeled with monoclonal antibodies and cellulose with an exoglucanase-gold complex. Cell wall polysaccharides were degraded differently by the two species. Pythium violae was responsible for degradations, which could be noticeable, especially for high methylesterified pectins, but which occurred after colonization and were localized near the hyphae. The conservation of integrity of diseased tissue was apparently due to the absence of degradation away from the hyphae. In contrast, P. ultimum was responsible for more extensive degradation of pectins and cellulose, which occurred at a relatively greater distance from the hyphae. Degradation of pectins was always more rapid in the cell walls than in the intercellular junctions. This phenomenon led to loss of tissue integrity and could explain the tissue maceration caused by P. ultimum infection. These differences in infection process are discussed in connection with the enzymic potential for degradation of cell wall polysaccharides.Key words: Daucus carota L., Pythium, pectin, cellulose, cytochemistry.
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Encinas, Osvaldo, and Geoffrey Daniel. "Degradation of the Gelatinous Layer in Aspen and Rubberwood by the Blue Stain Fungus Lasiodiplodia Theobromae." IAWA Journal 18, no. 2 (1997): 107–15. http://dx.doi.org/10.1163/22941932-90001471.
Повний текст джерелаАнотація:
Studies on the degradative ability of the blue stain fungus Lasiodiplodia theobromae (Pat.) Griffon ' Maublanc have shown several strains to cause significant weight losses (c. 20%) in wood of temperate and tropical species, aspen (Populus tremula) and rubberwood (Hevea brasiliensis), both species that commonly form tension wood. In addition to the consumption of soluble carbohydrates, major changes occurred in the ultrastructure of fibre cell walls, with a rapid attack of the G-layer of the gelatinous fibres. Following G-layer degradation, earlywood fibres of both species showed true cell wall degradation with pronounced erosion attack, suggesting that prior destruction of the G-layer afforded greater accessibility and ease of attack of the outer secondary cell wall layers.
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El-Assi, N., D. J. Huber, and J. K. Brecht. "Cell Wall Degradation in Irradiated Tomato Fruit." HortScience 30, no. 4 (July 1995): 815B—815. http://dx.doi.org/10.21273/hortsci.30.4.815b.
Повний текст джерелаАнотація:
The irradiation of harvested fruit is typically accompanied by excessive tissue softening, a process that is not well understood. In this study, we examined the role of specific cell wall polymers and the extent of general cell wall degradation and softening in irradiated tomato fruit. `Sunny' tomato fruit at mature-green and pink stages were subjected to X-ray radiation at 0, 83, and 156 Krad. Immediate softening was noted for both maturation classes, although some postirradiation recovery was evident in green fruit. Pectic polymers of both mature-green and pink fruit exhibited depolymerization and altered neutral sugar profiles in response to irradiation. Pectins, either as components of total ethanol-insoluble solids (EIS), purified by selective extraction, or of commercial origin were similarly affected by irradiation. Cellulose preparations were unaffected by irradiation. The data demonstrate that the effect of irradiation on the cell wall exhibits specificity, can occur nonenzymatically, and does not require initiating adducts of cytosolic origin.
Дисертації з теми "Cell wall degradation"
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Muda, Pauziah. "Cell wall degradation during mango fruit ripening." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316943.
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Taylor, Larry Edmund II. "Degradation of plant cell wall polysaccharides by saccharophagus degradans." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3242.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Marine-Estuarine-Environmental Sciences. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Wyles, Alison Maria. "Cell wall degradation in copper chrome arsenic treated wood." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46918.
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Zhang, Jianliang. "Pectinesterase and cell wall degradation in normal and transgenic tomatoes." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385230.
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Henshaw, Joanna Louise. "Analysis of protein-carbohydrate recognition in plant cell wall degradation." Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427298.
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Simons, Howard. "Use of multi-gene downregulation to study cell wall degradation during fruit ripening." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243756.
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Wang, Jiawei. "Thermal degradation reactivity of cellulose and hemicellulose in Japanese cedar and Japanese beech wood cell walls." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/264676.
Повний текст джерелаАнотація:
京都大学新制・課程博士
博士(エネルギー科学)
甲第23395号
エネ博第422号
新制||エネ||80(附属図書館)
京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻
(主査)教授 河本 晴雄, 教授 亀田 貴之, 教授 杉山 淳司
学位規則第4条第1項該当
Doctor of Energy Science
Kyoto University
DFAM
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Rajangam, Alex S. "Functional genomics of wood degradation and biosynthesis." Licentiate thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-592.
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Leite, Débora Chaves Coelho. "Modificações da parede celular durante a formação de aerênquima em raízes de cana-de-açúcar." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/41/41132/tde-07062013-110944/.
Повний текст джерелаАнотація:
Uma alternativa para aumentar a produção de bioetanol por área de cana plantada no Brasil seria utilizar os resíduos de sua biomassa para conversão em etanol. O conhecimento de como processos de degradação da parede celular se dão em plantas usadas para a produção de bioenergia e a compreensão de como eles funcionam pode ser de grande utilidade para esta tecnologia. Na investigação da anatomia de cana encontramos evidências da formação de um aerênquima lisígeno na raiz de cana, espaços gasosos no córtex da raiz decorrentes da morte celular e degradação da parede. Assim, decidiu-se aprofundar os estudos neste sistema através de técnicas de bioquímica de parede celular, microscopia de luz e transmissão e imunolocalização. A formação do aerênquima nas raízes de cana-de-açúcar tem início com a morte celular programada e a degradação de β-glucano e pectinas, principalmente daquelas associadas às lamelas médias, resultando na separação das células. As hemiceluloses arabinoxilano e xiloglucano mostram apenas modificações em suas estruturas finas, mas permanecendo nas paredes. Além disto, foram observados em microscopia de transmissão alguns pontos onde houve a degradação completa de parede celular, porém a presença de diversas paredes celulares colapsadas nas lamelas entre o aerênquima e ao seu redor parece ser mais importante para a formação do aerênquima. As modificações dos polissacarídeos estão possivelmente associadas com a alteração de características físicas das paredes, tornando-as mais suscetíveis a dobras e colapsos, gerando os espaços de gás e lamelas resistentes, que sustentam estes espaços. Mais do que a \"degradação da parede celular\", como é tratado em definições de aerênquima, pudemos observar que este fenômeno é resultado de uma sequência de eventos que permitem modificações da parede celular, e não necessariamente a sua completa degradação, resultando na abertura dos espaços gasososAn alternative to increase bioethanol production per area of sugarcane plantation in Brazil would be to use its biomass residue for conversion into ethanol. The knowledge of how cell wall degradation processes occur in plants used for bioenergy production and understanding how they work can be of great use for this technology. Studying the sugarcane anatomy, we found evidences for the formation of a lysigenous aerenchyma in the roots, gas spaces in the root cortex originated from cell death and cell wall degradation. Thus, we decided to deepen the studies in this system using cell wall biochemistry, light and transmission microscopy and immunolabeling. The aerenchyma formation in sugarcane roots starts with programmed cell death and degradation of β-glucan and pectins, especially those from middle lamellae, resulting in cell separation. The hemicelluloses arabinoxylan and xyloglucan only show modifications in fine structure, but they remain in the cell wall. Besides, complete cell wall degradation was observed in a few spots through transmission electron microscopy, although the collapsing of cell walls seems to be more important for aerenchyma formation. Modifications in the polysaccharides are possibly associated with changes in cell wall physical properties, making them more susceptible to folding and collapsing, generating gas spaces and resistant lamellae that support these spaces. Described as \"cell wall degradation\" in aerenchyma definition in literature, we observed that this phenomenon is the result of a series of events that allow cell wall modifications, and not necessarily its complete degradation, resulting in the formation of gas spaces
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Nouala, Fonkou Simplice. "Comparison of plant cell wall degrading community in the rumen of N'Dama and N'Dama x Jersey crossbred cattle in relation to in vivo and in vitro cell wall degradation." Hohenheim : University of Hohenheim, Institute of Animal Production in the Tropics and Subtropics, Aquaculture Systems and Animal Nutrition in the Tropics and Subtropics, 2004. http://opus-ho.uni-stuttgart.de/hop/volltexte/2004/59/pdf/noualathesis.pdf.
Повний текст джерелаКниги з теми "Cell wall degradation"
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Nordkvist, Erik. Composition and degradation of cell walls in red clover, lucerne and cereal straw. Uppsala: Swedish University of Agricultural Sciences, 1987.
Знайти повний текст джерелаЧастини книг з теми "Cell wall degradation"
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Brett, C., and K. Waldron. "Cell-wall degradation." In Physiology and Biochemistry of Plant Cell Walls, 168–79. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-010-9641-6_8.
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Kubicek, Christian P., Verena Seidl, and Bernhard Seiboth. "Plant Cell Wall and Chitin Degradation." In Cellular and Molecular Biology of Filamentous Fungi, 396–413. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555816636.ch27.
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Chesson, Andrew. "Mechanistic Models of Forage Cell Wall Degradation." In Forage Cell Wall Structure and Digestibility, 347–76. Madison, WI, USA: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, 2015. http://dx.doi.org/10.2134/1993.foragecellwall.c14.
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Van Soest, P. J. "Cell Wall Matrix Interactions and Degradation-Session Synopsis." In Forage Cell Wall Structure and Digestibility, 377–95. Madison, WI, USA: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, 2015. http://dx.doi.org/10.2134/1993.foragecellwall.c15.
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Pell, Alice N., and Peter Schofield. "Microbial Adhesion and Degradation of Plant Cell Walls." In Forage Cell Wall Structure and Digestibility, 397–423. Madison, WI, USA: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, 2015. http://dx.doi.org/10.2134/1993.foragecellwall.c16.
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Glenn, Barbara P., and Dale R. Waldo. "Cell Wall Degradation in the Ruminant-Session Synopsis." In Forage Cell Wall Structure and Digestibility, 603–20. Madison, WI, USA: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, 2015. http://dx.doi.org/10.2134/1993.foragecellwall.c23.
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Weimer, Paul J. "Microbial and Molecular Mechanisms of Cell Wall Degradation-Session Synopsis." In Forage Cell Wall Structure and Digestibility, 485–98. Madison, WI, USA: American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, 2015. http://dx.doi.org/10.2134/1993.foragecellwall.c19.
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Davis, Eric L., Annelies Haegeman, and Taisei Kikuchi. "Degradation of the Plant Cell Wall by Nematodes." In Genomics and Molecular Genetics of Plant-Nematode Interactions, 255–72. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-0434-3_12.
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Ramoni, Jonas, and Bernhard Seiboth. "6 Degradation of Plant Cell Wall Polymers by Fungi." In Environmental and Microbial Relationships, 127–48. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-29532-9_6.
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Joseleau, Jean-Paul, and Katia Ruel. "Enzyme Excretion During Wood Cell Wall Degradation byPhanerochaete chrysosporium." In ACS Symposium Series, 443–53. Washington, DC: American Chemical Society, 1989. http://dx.doi.org/10.1021/bk-1989-0399.ch032.
Повний текст джерелаТези доповідей конференцій з теми "Cell wall degradation"
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Salahudeen Rafeeka, Rinsa, Aditya Kurup, and Mayanglambam Suheshkumar Singh. "Investigation on methanol induced cell wall degradation in plants using home-built LSFM system." In Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues XX, edited by James F. Leary, Attila Tarnok, and Jessica P. Houston. SPIE, 2022. http://dx.doi.org/10.1117/12.2609997.
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Carroll, Gráinne T., Paul D. Devereux, Anthony Callanan, Tim M. McGloughlin, and Michael T. Walsh. "The Influence of Realistic Arteriovenous (AV) Fistula Wall Shear Stress (WSS) on Endothelial Cell (EC) Gene Expression: A Correlation to Intimal Hyperplasia Development." In ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-193248.
Повний текст джерелаАнотація:
The low patency rates of Arteriovenous (AV) fistulae are well documented in the literature [1]. Up to 90% of AV fistula morbidity is caused by stenotic lesion formation and the subsequent development of thrombosis in the Vascular Access (VA) junction [1]. The underlying pathology of these stenotic lesions is intimal hyperplasia (IH) which has been characterized by the degradation of the extra cellular matrix (ECM), migration and proliferation of smooth muscle cells (SMCs) and the infiltration of leukocytes and monocytes into the intima. IH primarily occurs in a number of key locations within the VA junction of AV fistulae which include the suture line of the anastomosis, on the floor of the vein opposite the VA junction and downstream of the anastomosis within the venous conduit of the AV fistula [2].
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Nagy, J. A., and H. F. Devorak. "FIBRINOGEN INFLUX AND FIBRIN ACCUMULATION IN ASCITES TUMORS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643668.
Повний текст джерелаАнотація:
Fibrin gel matrix organizes solid tumors into discrete cell nests and providesa provisional matrix for mature stroma generation. Fibrin deposits result fromlocal extravasation of plasma fibrinogen followed by extravascular coagulationand crosslinking. Unlike solid tumors, ascites tumor cells in body cavities grow in suspension, and are not envelopedin fibrin gel. The lack of fibrin gel in ascites tumors has several possible explanations: 1. Peritoneal wall blood vessels are impermeable to molecules as large as fibrinogen. 2. Fibrinogen leaks from peritoneal vessels, but is clotted to fibrin and never reaches the peritoneal cavity. 3. Fibrinogen leaks from vessels, reaches the peritoneal cavity, and is rapidly degraded. To distinguish among these possibilities we investigated the permselective properties of the peritoneal wall. We measured the influx of intravenously (iv) administered, fluorescein-labeled dextrans (FITC-D) of varying size into the peritonea of normal and tumor or inflammatory ascites-bearing mice and guinea pigs. FITC-D of MW 70-5,000 kD leaked from vessels and ∽ 10-fold more entered MOT or TA3/St tumor-associated or serotonin-induced inflammatory ascites than normal peritonea. In tumor bearing animals, 3-20% of injected FITC-D entered the peritoneum within 15-30 min., all of it intact by gel exclusion chromatography. We also investigated the influx of fluorescein-labeled fibrinogen (FITC-F). At 30-60 min after iv injection, FITC-F hadextravasated into the peritoneal wall as judged by fluorescence microscopy (tumor bearing ≫ normal animals). Moreover, monoclonal antibodies reactivewith fibrin, but not fibrinogen, stained such deposits by immunohistochemistry in guinea pigs bearing line 1 or line 10 ascites tumors. Following iv injection of 125l-fibrinogen, as much as 11% of injected radioactivity accumulated in tumor ascites fluid over1-3 hrs (versus ∽1% in normal controls). In both, only ∽half was clottableand 3040% was of low MW (≤.10 kD). In contrast, iv 125I-albumin also entered the peritoneal cavity at an enhanced rate but showed no evidence of degradation. We conclude that fibrinogen extravasates from peritoneal vessels,thatleakage is increased in ascites tumor-bearing animals, and that fibrinogen clots, at least in part, before it enters the peritoneal cavity. Also, fibrinogen undergoes selective degradation and much of the fibrinogen that does enter the peritoneum represents degradation products of fibrinogen/fibrin. The resulting lack of peritoneal fibrin gel matrixfavors the suspension pattern of ascites, as compared with solid tumor growth.
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Moharana, Manoj Kumar, Rohan M. Nemade, and Sameer Khandekar. "Phase-Change Heat Transfer of Ethanol-Water Mixtures: Towards Development of a Distributed Hydrogen Generator." In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17668.
Повний текст джерелаАнотація:
Hydrogen fuel from renewable bio-ethanol is a potentially strong contender as an energy carrier. Its distributed production by steam reforming of ethanol on microscale platforms is an efficient upcoming method. Such systems require (a) a pre-heater for liquid to vapor conversion of ethanol water mixtures (b) a gas-phase catalytic reactor. We focus on the fundamental experimental heat transfer studies (pool and flow boiling of ethanol-water mixtures) required for the primary pre-heater boiler design. Flow boiling results (in a 256 μm square channel) clearly show the influence of mixture composition. Heat transfer coefficient remains almost constant in the single-phase region and rapidly increases as the two-phase region starts. On further increasing the wall superheat, heat transfer starts to decrease. At higher applied heat flux, the channel is subjected to axial back conduction from the single-phase vapor region to the two-phase liquid-vapor region, thus raising local wall temperatures. Simultaneously, to gain understanding of phase-change mechanisms in binary mixtures and to generate data for the modeling of flow boiling process, pool-boiling of ethanol-water mixtures has also been initiated. After benchmarking the setup against pure fluids, variation of heat transfer coefficient, bubble growth, contact angles, are compared at different operating conditions. Results show strong degradation in heat transfer in mixtures, which increases with operating temperature.
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Kyle B Sander and Ganti S Murthy. "Enzymatic Degradation of Microalgal Cell Walls." In 2009 Reno, Nevada, June 21 - June 24, 2009. St. Joseph, MI: American Society of Agricultural and Biological Engineers, 2009. http://dx.doi.org/10.13031/2013.27044.
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Wan, William, Laura Hansen, and Rudolph L. Gleason. "A 3-D Constrained Mixture Model for Vascular Growth and Remodeling." In ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206778.
Повний текст джерелаАнотація:
It is known that arteries adapt and remodel to changes in their loading conditions. Evolution of mechanical properties of blood vessels is associated with numerous chronic and acute conditions such as hypertension and coronary thrombosis. In addition, treatments such as bypass surgery create loading conditions not seen in normal arteries. Blood vessels used in coronary bypass grafts experience abnormal loading conditions in both circumferential and axial directions. Blood vessels remodel by altering structural components to restore homeostatic values of stress. Such changes may include smooth muscle cell proliferation, migration and collagen synthesis, degradation, and remodeling. While biaxial mechanical tests and organ culture experiments provide values for global variables such as mean stresses and total thickness, mathematical models can help describe local mechanical properties at locations throughout the vessel wall. Experimental observations suggest that constituents of arteries turnover at different rates; thus, it is important that models are able to track individual constituents of the artery separately. Here, we present a 3D constrained mixture model for growth and remodeling of arteries exposed to large changes in flow, pressure, and axial stretch -induced.
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Fanney, A. Hunter, Brian P. Dougherty, and Mark W. Davis. "A Comparison of Predicted to Measured Photovoltaic Module Performance." In ASME 2007 Energy Sustainability Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/es2007-36028.
Повний текст джерелаАнотація:
Computer simulation models to accurately predict the electrical performance of photovoltaic modules are essential. Without such models, potential purchasers of photovoltaic systems have insufficient information to judge the relative merits and cost effectiveness of photovoltaic systems. The purpose of this paper is to compare the predictions of a simulation model, developed by Sandia National Laboratories, to measurements from photovoltaic modules installed in a vertical wall fac¸ade in Gaithersburg, MD. The photovoltaic modules were fabricated using monocrystalline, polycrystalline, tandem-junction amorphous, and copper-indium diselenide cells. Polycrystalline modules were constructed using three different glazing materials — 6 mm low-iron glass, 2 mm ethylene-tetrafluoroethylene copolymer (ETFE), and 2 mm polyvinylidene fluoride (PVDF). In order to only assess the simulation model’s ability to predict photovoltaic module performance, measured solar radiation data in the plane of the modules is initially used. Additional comparisons are made using horizontal radiation measurements. The ability of the model to accurately predict the temperature of the photovoltaic cells is investigated by comparing predicted energy production using measured versus predicted photovoltaic cell temperatures. The model was able to predict the measured annual energy production of the photovoltaic modules, with the exception of the tandem-junction amorphous modules, to within 6% using vertical irradiance measurements. The model overpredicted the annual energy production by approximately 14% for the tandem-junction amorphous panels. Using measured horizontal irradiance as input to the simulation model, the agreement between measured and predicted annual energy predictions varied between 1% and 8%, again with the exception of the tandem-junction amorphous silicon modules. The large difference between measured and predicted results for the tandem-junction modules is attributed to performance degradation. Power measurements of the tandem-junction amorphous modules at standard reporting conditions prior to and after exposure revealed a 12% decline. Supplying post-exposure module parameters to the model resulting in energy predictions within 5% of measured values.
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Orfila, Caroline, Florence Dal Degan, Peter Ulvskov, and Henrik V. Scheller. "BIOSYNTHESIS AND DEGRADATION OF O-ACETYLATED PECTIC POLYSACCHARIDES IN PLANT PRIMARY CELL WALLS." In XXIst International Carbohydrate Symposium 2002. TheScientificWorld Ltd, 2002. http://dx.doi.org/10.1100/tsw.2002.404.
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Hawiger, J. "PLATELET RECEPTOR RECOGNITION DOMAINS AND THEIR SYNTHETIC PEPTIDE ANALOGS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643726.
Повний текст джерелаАнотація:
Adhesive molecules and their receptorsplay an essential role in hemostasis and thrombosis. Platelet thrombi are formed through the interaction of cell adhesion molecules (CAMs) with intercellular adhesion molecules (IAMs)and substrate adhesion molecules (SAMs). Platelet CAMs encompass membrane glycoproteins lb, lib, Ilia,and possibly la and IV, which constitutemembrane receptors for IAMs(e.g., fibrinogen) and for SAMs encompassingvon Willebrand Factor (vWF), fibronectin, vitronectin, collagen, and thrcmbospondin. Receptorfunction of platelet CAMs can be specific,i.e., only one adhesive protein among IAMs and SAMs is selected forbinding as exemplified by GPIb and vWF. Alternatively,more than one adhesive protein can interact with platelet CAMs comprising the GPIIb/IIIa complex.This common adhesive receptor mechanism switched on by thrombin, ADP, phorbol ester or ionophore A23187 is turned off by a rise in intraplatelet cyclic AMP which provides a negative control.Fibrinogen, the most abundant adhesiveprotein in plasma, interacts with platelet CAMs via receptor recognition domains on gamma and alpha chains. Pinpointing platelet receptor recognition domain to a carboxy-terminal segment of the gamma chain encompassing residues 400-411gave rise to a series of synthetic peptide analogs which do not interfere with themetabolic pathways of platelets but blockbinding of I fibrinogen to its receptors on stimulated platelets, inhibit their aggregation in vitro, and formation of a platelet thrombus in vivo. The alpha chain of human fibrinogen contains the sequenceRGD (residues 95-97 and 572-574). Synthetpeptide analogs of the RGD sequence, which constitute the "cell adhesion site" of fibronectin, also inhibit binding of 125I-fibrinogen to stimulated platelets. However, these synthetic peptides are not "specific" for fibrinogen chains because thealpha chain of human fibrinogen which hasnosequence homology with gamma 400-411 is prevented by a peptide gamma 400-411 from interaction with platelet receptors. Viceversa, the human gamma chain is blocked by tetrapeptide RGDS not expressed in the human gamma chain. Interaction of human vWF with human platelets is blocked by synthetic peptide analogs of gamma 400-411 (not present in vWF)and of RGD sequence (present in vWF).These synthetic peptides inhibite "common" receptor pathwaystimulated with ADP, thrombin, or phorbolester, but they do not interfere with binding of 125I-vWF via a "specific" pathvoy induced with ristocetin and involving GPIb.The design of synthetic peptide analogs which inhibit platelet receptors for adhesive molecules includes the following considerations: ligand specificity (is thepeptide inhibitory toward binding of one or more adhesive molecules?),cell speciicity (is the peptide specific for platelets or does it perturb the adhesive properties of other cells, e.g.,endothelium?);the hydrophilic character; protection against degradation by peptidases; and a sufficiently long half-life to achieve platelet inhibitory potency in vivo without overloading the blood with excessive amounts of peptide.This is accomplished by constructing a peptide-albumin conjugate with ahalf-life extended at least 30 times.Whenpeptides are modeled with predominantly hydrophilic or hydrophobic residues, only the hydrophilic peptide remained active to block the platelet receptor. This agreed with the general observation that sequences on adhesive molecules that are knownto interact with cellular receptors have a hydrophilic rather than a hydrophobic character. Furthermore, changing the charge of synthetic peptides toward the negative reduced the reactivity, whereas introducing additional arginine residues enhanced the reactivity toward platelet receptors. Localization of the functionally important binding domain in the flexible segment of an adhesive protein increases the likelihood that the synthetic peptide will assume the conformation mimicking such a domain in the native adhesive protein. Structure-function studies of the receptor recognition domains on adhesive molecules led to development of a new class of platelet inhibitors acting at the membranereceptors responsible for anchoring of platelets to the vessel wall and linking them to each other.
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Kakadjian, Sarkis, Keith Korhonen, Marvin Solomon, Jarrett Kitchen, Amanuel Gebrekirstos, Jesse Risner, and Otman Algadi. "Effective Water Treatment in the Permian and Marcellus Shales to Mitigate Surface Equipment Failures." In SPE Annual Technical Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/210250-ms.
Повний текст джерелаАнотація:
Abstract Chemical and oxidative biocides are designed to sanitize water by reducing aerobic and anaerobic bacterial populations in the fresh, brackish and reclaimed source waters. These biocides are used extensively in high-rate fracture stimulations to reduce formation damage, chemical degradation, biogenic H2S and microbial induced corrosion (MIC). Oxidative biocides work by removing electrons from the cell wall of aerobic and anaerobic bacteria. The same electron transfer mechanism can be detrimental to surface equipment. This study presents the impact of several oxidative biocides on the corrosion rate and pitting of different frac iron alloys and how those biocides effect the mechanical integrity of elastomer seals. It also presents different remediation methods to mitigate their oxidative effects. The oxidative biocides tested were Chlorine, Chlorine Dioxide and a Peracidic Acid blend. The corrosion rate of the iron alloys coupons was measured by weight loss analysis. This method can measure the rate of corrosion in pounds per square foot at time and was used to compare the impact of different residual oxidizers on the corrosion rate of the ground iron. Structural changes to the elastomers were detected visually. The results of the study showed that the corrosion rate varied depending on the alloy/residual oxidative biocide combination. Usually, Peracidic Acid blend or Chlorine had the highest corrosion rates across all alloys tested; depending on the oxidative biocide/alloy combination, the corrosion rate could vary by a factor of 2X over the nine-week timeframe. Elastomer testing over 6 weeks showed variability in the types of structural changes depending on the concentration and oxidative biocide tested. The lab and field testing included onsite monitoring of the corrosion rate, oxidation reduction potential (ORP), oxygen in solution and determination of the Langelier Saturation Index (LSI). The methodology has been effective in predicting iron failures related to the composition of the water and/or presence of oxidizers. Chemical solutions implemented to mitigate the surface iron failures included use of intermittent blends of water-soluble quaternary amines and surfactants. Since these remediation attempts have started, the replacement cost of frac iron has decreased from over 550K US$ per month, per frac spread to none, over a 3-month period.
Звіти організацій з теми "Cell wall degradation"
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David B. Wilson. IDENTIFICATION AND CHARACTERIZATION OF THERMOBIFIDA FUSCA GENES INVOLVED IN PLANT CELL WALL DEGRADATION. Office of Scientific and Technical Information (OSTI), January 2006. http://dx.doi.org/10.2172/862421.
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Carpita, Nicholas C., Ruth Ben-Arie, and Amnon Lers. Pectin Cross-Linking Dynamics and Wall Softening during Fruit Ripening. United States Department of Agriculture, July 2002. http://dx.doi.org/10.32747/2002.7585197.bard.
Повний текст джерелаАнотація:
Our study was designed to elucidate the chemical determinants of pectin cross-linking in developing fruits of apple and peach and to evaluate the role of breakage cross-linkages in swelling, softening, and cell separation during the ripening. Peaches cell walls soften and swell considerably during the ripening, whereas apples fruit cells maintain wall firmness but cells separate during late stages of ripening. We used a "double-reduction" technique to show that levels of non-methyl esters of polyuronic acid molecules were constant during the development and ripening and decreased only in overripe fruit. In peach, methyl and non-methyl esters increased during the development and decreased markedly during the ripening. Non-methyl ester linkages in both fruit decreased accompanied fruit softening. The identity of the second component of the linkage and its definitive role in the fruit softening remain elusive. In preliminary examination of isolated apples cell walls, we found that phenolic compounds accumulate early in wall development but decrease markedly during ripening. Quantitative texture analysis was used to correlate with changes to wall chemistry from the fresh-picked ripe stage to the stage during storage when the cell separation occurs. Cell wall composition is similar in all cultivars, with arabinose as the principal neutral sugar. Extensive de-branching of these highly branched arabinans pre-stages softening and cell-cell separation during over-ripening of apple. The longer 5-arabinans remain attached to the major pectic polymer rhamnogalacturonan I (RG I) backbone. The degree of RG I branching, as judged from the ratios of 2-Rha:2,4-Rha, also decreases, specially after an extensive arabinan de-branching. Loss of the 4-Rham linkages correlated strongly with the softening of the fruit. Loss of the monomer or polymer linked to the RG I produce directly or indirectly the softening of the fruit. This result will help to understand the fruit softening and to have better control of the textural changes in fruit during the ripening and especially during the storage. 'Wooliness', an undesirable mealy texture that is induced during chilling of some peach cultivars, greatly reduces the fruit storage possibilities. In order to examine the hypothesis that the basis for this disorder is related to abnormality in the cell wall softening process we have carried out a comparative analysis using the resistant cultivar, Sunsnow, and a sensitive one, Hermosa. We investigated the activity of several pectin- and glycan-modifying enzymes and the expression of their genes during ripening, chilling, and subsequent shelf-life. The changes in carbohydrate status and in methyl vs. non-methyl uronate ester levels in the walls of these cultivars were examined as well to provide a basis for comparison of the relevant gene expression that may impact appearance of the wooly character. The activities of the specific polygalacturonase (PGase) and a CMC-cellulase activities are significantly elevated in walls of peaches that have become wooly. Cellulase activities correlated well with increased level of the transcript, but differential expression of PGase did not correspond with the observed pattern of mRNA accumulation. When expression of ethylene biosynthesis related genes was followed no significant differences in ACC synthase gene expression was observed in the wooly fruit while the normal activation of the ACC oxidase was partially repressed in the Hermosa wooly fruits. Normal ripening-related loss of the uronic acid-rich polymers was stalled in the wooly Hermosa inconsistent with the observed elevation in a specific PGase activity but consistent with PG gene expression. In general, analysis of the level of total esterification, degree of methyl esterification and level of non-methyl esters did not reveal any major alterations between the different fruit varieties or between normal and abnormal ripening. Some decrease in the level of uronic acids methyl esterification was observed for both Hermosa and Sunsnow undergoing ripening following storage at low temperature but not in fruits ripening after harvest. Our results support a role for imbalanced cell wall degradation as a basis for the chilling disorder. While these results do not support a role for the imbalance between PG and pectin methyl esterase (PME) activities as the basis for the disorder they suggest a possible role for imbalance between cellulose and other cell wall polymer degradation during the softening process.
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Shomer, Ilan, Ruth E. Stark, Victor Gaba, and James D. Batteas. Understanding the hardening syndrome of potato (Solanum tuberosum L.) tuber tissue to eliminate textural defects in fresh and fresh-peeled/cut products. United States Department of Agriculture, November 2002. http://dx.doi.org/10.32747/2002.7587238.bard.
Повний текст джерелаАнотація:
The project sought to understand factors and mechanisms involved in the hardening of potato tubers. This syndrome inhibits heat softening due to intercellular adhesion (ICA) strengthening, compromising the marketing of industrially processed potatoes, particularly fresh peeled-cut or frozen tubers. However, ICA strengthening occurs under conditions which are inconsistent with the current ideas that relate it to Ca-pectate following pectin methyl esterase (PME) activity or to formation of rhamnogalacturonan (RG)-II-borate. First, it was necessary to induce strengthening of the middle lamellar complex (MLX) and the ICA as a stress response in some plant parenchyma. As normally this syndrome does not occur uniformly enough to study it, we devised an efficient model in which ICA-strengthening is induced consistently under simulated stress by short-chain, linear, mono-carboxylic acid molecules (OAM), at 65 oC [appendix 1 (Shomer&Kaaber, 2006)]. This rapid strengthening was insufficient for allowing the involved agents assembly to be identifiable; but it enabled us to develop an efficient in vitro system on potato tuber parenchyma slices at 25 ºC for 7 days, whereas unified stress was reliably simulated by OAMs in all the tissue cells. Such consistent ICA-strengthening in vitro was found to be induced according to the unique physicochemical features of each OAM as related to its lipophilicity (Ko/w), pKa, protonated proportion, and carbon chain length by the following parameters: OAM dissociation constant (Kdiss), adsorption affinity constant (KA), number of adsorbed OAMs required for ICA response (cooperativity factor) and the water-induced ICA (ICAwater). Notably, ICA-strengthening is accompanied by cell sap leakage, reflecting cell membrane rupture. In vitro, stress simulation by OAMs at pH<pKa facilitated the consistent assembly of ICAstrengthening agents, which we were able to characterize for the first time at the molecular level within purified insoluble cell wall of ICA-strengthened tissue. (a) With solid-state NMR, we established the chemical structure and covalent binding to cell walls of suberin-like agents associated exclusively with ICA strengthening [appendix 3 (Yu et al., 2006)]; (b) Using proteomics, 8 isoforms of cell wall-bound patatin (a soluble vacuolar 42-kDa protein) were identified exclusively in ICA-strengthened tissue; (c) With light/electron microscopy, ultrastructural characterization, histochemistry and immunolabeling, we co-localized patatin and pectin in the primary cell wall and prominently in the MLX; (d) determination of cell wall composition (pectin, neutral sugars, Ca-pectate) yielded similar results in both controls and ICA-strengthened tissue, implicating factors other than PME activity, Ca2+ or borate ions; (e) X-ray powder diffraction experiments revealed that the cellulose crystallinity in the cell wall is masked by pectin and neutral sugars (mainly galactan), whereas heat or enzymatic pectin degradation exposed the crystalline cellulose structure. Thus, we found that exclusively in ICA-strengthened tissue, heat-resistant pectin is evident in the presence of patatin and suberinlike agents, where the cellulose crystallinity was more hidden than in fresh control tissue. Conclusions: Stress response ICA-strengthening is simulated consistently by OAMs at pH< pKa, although PME and formation of Ca-pectate and RG-II-borate are inhibited. By contrast, at pH>pKa and particularly at pH 7, ICA-strengthening is mostly inhibited, although PME activity and formation of Ca-pectate or RG-II-borate are known to be facilitated. We found that upon stress, vacuolar patatin is released with cell sap leakage, allowing the patatin to associate with the pectin in both the primary cell wall and the MLX. The stress response also includes formation of covalently bound suberin-like polyesters within the insoluble cell wall. The experiments validated the hypotheses, thus led to a novel picture of the structural and molecular alterations responsible for the textural behavior of potato tuber. These findings represent a breakthrough towards understanding of the hardening syndrome, laying the groundwork for potato-handling strategies that assure textural quality of industrially processed particularly in fresh peeled cut tubers, ready-to-prepare and frozen preserved products.
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Manulis, Shulamit, Christine D. Smart, Isaac Barash, Guido Sessa, and Harvey C. Hoch. Molecular Interactions of Clavibacter michiganensis subsp. michiganensis with Tomato. United States Department of Agriculture, January 2011. http://dx.doi.org/10.32747/2011.7697113.bard.
Повний текст джерелаАнотація:
Clavibacter michiganensis subsp. michiganensis (Cmm), the causal agent of bacterial wilt and canker of tomato, is the most destructive bacterial disease of tomato causing substantial economic losses in Israel, the U.S.A. and worldwide. The molecular strategies that allow Cmm, a Gram-positive bacterium, to develop a successful infection in tomato plants are largely unknown. The goal of the project was to elucidate the molecular interactions between Cmmand tomato. The first objective was to analyze gene expression profiles of susceptible tomato plants infected with pathogenic and endophytic Cmmstrains. Microarray analysis identified 122 genes that were differentially expressed during early stages of infection. Cmm activated typical basal defense responses in the host including induction of defense-related genes, production of scavenging of free oxygen radicals, enhanced protein turnover and hormone synthesis. Proteomic investigation of the Cmm-tomato interaction was performed with Multi-Dimensional Protein Identification Technology (MudPIT) and mass spectroscopy. A wide range of enzymes secreted by Cmm382, including cell-wall degrading enzymes and a large group of serine proteases from different families were identified in the xylem sap of infected tomato. Based on proteomic results, the expression pattern of selected bacterial virulence genes and plant defense genes were examined by qRT-PCR. Expression of the plasmid-borne cellulase (celA), serine protease (pat-1) and serine proteases residing on the chp/tomA pathogenicity island (chpCandppaA), were significantly induced within 96 hr after inoculation. Transcription of chromosomal genes involved in cell wall degradation (i.e., pelA1, celB, xysA and xysB) was also induced in early infection stages. The second objective was to identify by VIGS technology host genes affecting Cmm multiplication and appearance of disease symptoms in plant. VIGS screening showed that out of 160 tomato genes, which could be involved in defense-related signaling, suppression of 14 genes led to increase host susceptibility. Noteworthy are the genes Snakin-2 (inhibitor of Cmm growth) and extensin-like protein (ELP) involved in cell wall fortification. To further test the significance of Snakin -2 and ELP in resistance towards Cmm, transgenic tomato plants over-expressing the two genes were generated. These plants showed partial resistance to Cmm resulting in a significant delay of the wilt symptoms and reduction in size of canker lesion compared to control. Furthermore, colonization of the transgenic plants was significantly lower. The third objective was to assess the involvement of ethylene (ET), jasmonate (JA) and salicylic acid (SA) in Cmm infection. Microarray and proteomic studies showed the induction of enzymes involved in ET and JA biosynthesis. Cmm promoted ET production 8 days after inoculation and SIACO, a key enzyme of ET biosynthesis, was upregulated. Inoculation of the tomato mutants Never ripe (Nr) impaired in ET perception and transgenic plants with reduced ET synthesis significantly delayed wilt symptoms as compared to the wild-type plants. The retarded wilting in Nr plants was shown to be a specific effect of ET insensitivity and was not due to altered expression of defense related genes, reduced bacterial population or decrease in ethylene biosynthesis . In contrast, infection of various tomato mutants impaired in JA biosynthesis (e.g., def1, acx1) and JA insensitive mutant (jai1) yielded unequivocal results. The fourth objective was to determine the role of cell wall degrading enzymes produced by Cmm in xylem colonization and symptoms development. A significance increase (2 to 7 fold) in expression of cellulases (CelA, CelB), pectate lyases (PelA1, PelA2), polygalacturonase and xylanases (XylA, XylB) was detected by qRT-PCR and by proteomic analysis of the xylem sap. However, with the exception of CelA, whose inactivation led to reduced wilt symptoms, inactivation of any of the other cell wall degrading enzymes did not lead to reduced virulence. Results achieved emphasized the complexity involved in Cmm-tomato interactions. Nevertheless they provide the basis for additional research which will unravel the mechanism of Cmm pathogenicity and formulating disease control measures.
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Epel, Bernard L., Roger N. Beachy, A. Katz, G. Kotlinzky, M. Erlanger, A. Yahalom, M. Erlanger, and J. Szecsi. Isolation and Characterization of Plasmodesmata Components by Association with Tobacco Mosaic Virus Movement Proteins Fused with the Green Fluorescent Protein from Aequorea victoria. United States Department of Agriculture, September 1999. http://dx.doi.org/10.32747/1999.7573996.bard.
Повний текст джерелаАнотація:
The coordination and regulation of growth and development in multicellular organisms is dependent, in part, on the controlled short and long-distance transport of signaling molecule: In plants, symplastic communication is provided by trans-wall co-axial membranous tunnels termed plasmodesmata (Pd). Plant viruses spread cell-to-cell by altering Pd. This movement scenario necessitates a targeting mechanism that delivers the virus to a Pd and a transport mechanism to move the virion or viral nucleic acid through the Pd channel. The identity of host proteins with which MP interacts, the mechanism of the targeting of the MP to the Pd and biochemical information on how Pd are alter are questions which have been dealt with during this BARD project. The research objectives of the two labs were to continue their biochemical, cellular and molecular studies of Pd composition and function by employing infectious modified clones of TMV in which MP is fused with GFP. We examined Pd composition, and studied the intra- and intercellular targeting mechanism of MP during the infection cycle. Most of the goals we set for ourselves were met. The Israeli PI and collaborators (Oparka et al., 1999) demonstrated that Pd permeability is under developmental control, that Pd in sink tissues indiscriminately traffic proteins of sizes of up to 50 kDa and that during the sink to source transition there is a substantial decrease in Pd permeability. It was shown that companion cells in source phloem tissue export proteins which traffic in phloem and which unload in sink tissue and move cell to cell. The TAU group employing MP:GFP as a fluorescence probe for optimized the procedure for Pd isolation. At least two proteins kinases found to be associated with Pd isolated from source leaves of N. benthamiana, one being a calcium dependent protein kinase. A number of proteins were microsequenced and identified. Polyclonal antibodies were generated against proteins in a purified Pd fraction. A T-7 phage display library was created and used to "biopan" for Pd genes using these antibodies. Selected isolates are being sequenced. The TAU group also examined whether the subcellular targeting of MP:GFP was dependent on processes that occurred only in the presence of the virus or whether targeting was a property indigenous to MP. Mutant non-functional movement proteins were also employed to study partial reactions. Subcellular targeting and movement were shown to be properties indigenous to MP and that these processes do not require other viral elements. The data also suggest post-translational modification of MP is required before the MP can move cell to cell. The USA group monitored the development of the infection and local movement of TMV in N. benthamiana, using viral constructs expressing GFP either fused to the MP of TMV or expressing GFP as a free protein. The fusion protein and/or the free GFP were expressed from either the movement protein subgenomic promoter or from the subgenomic promoter of the coat protein. Observations supported the hypothesis that expression from the cp sgp is regulated differently than expression from the mp sgp (Szecsi et al., 1999). Using immunocytochemistry and electron microscopy, it was determined that paired wall-appressed bodies behind the leading edge of the fluorescent ring induced by TMV-(mp)-MP:GFP contain MP:GFP and the viral replicase. These data suggest that viral spread may be a consequence of the replication process. Observation point out that expression of proteins from the mp sgp is temporary regulated, and degradation of the proteins occurs rapidly or more slowly, depending on protein stability. It is suggested that the MP contains an external degradation signal that contributes to rapid degradation of the protein even if expressed from the constitutive cp sgp. Experiments conducted to determine whether the degradation of GFP and MP:GFP was regulated at the protein or RNA level, indicated that regulation was at the protein level. RNA accumulation in infected protoplast was not always in correlation with protein accumulation, indicating that other mechanisms together with RNA production determine the final intensity and stability of the fluorescent proteins.
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Morrison, Mark, Joshuah Miron, Edward A. Bayer, and Raphael Lamed. Molecular Analysis of Cellulosome Organization in Ruminococcus Albus and Fibrobacter Intestinalis for Optimization of Fiber Digestibility in Ruminants. United States Department of Agriculture, March 2004. http://dx.doi.org/10.32747/2004.7586475.bard.
Повний текст джерелаАнотація:
Improving plant cell wall (fiber) degradation remains one of the highest priority research goals for all ruminant enterprises dependent on forages, hay, silage, or other fibrous byproducts as energy sources, because it governs the provision of energy-yielding nutrients to the host animal. Although the predominant species of microbes responsible for ruminal fiber degradation are culturable, the enzymology and genetics underpinning the process are poorly defined. In that context, there were two broad objectives for this proposal. The first objective was to identify the key cellulosomal components in Ruminococcus albus and to characterize their structural features as well as regulation of their expression, in response to polysaccharides and (or) P AA/PPA. The second objective was to evaluate the similarities in the structure and architecture of cellulosomal components between R. albus and other ruminal and non-ruminal cellulolytic bacteria. The cooperation among the investigators resulted in the identification of two glycoside hydrolases rate-limiting to cellulose degradation by Ruminococcus albus (Cel48A and CeI9B) and our demonstration that these enzymes possess a novel modular architecture specific to this bacterium (Devillard et al. 2004). We have now shown that the novel X-domains in Cel48A and Cel9B represent a new type of carbohydrate binding module, and the enzymes are not part of a ceiluiosome-like complex (CBM37, Xu et al. 2004). Both Cel48A and Cel9B are conditionally expressed in response to P AA/PPA, explaining why cellulose degradation in this bacterium is affected by the availability of these compounds, but additional studies have shown for the first time that neither PAA nor PPA influence xylan degradation by R. albus (Reveneau et al. 2003). Additionally, the R. albus genome sequencing project, led by the PI. Morrison, has supported our identification of many dockerin containing proteins. However, the identification of gene(s) encoding a scaffoldin has been more elusive, and recombinant proteins encoding candidate cohesin modules are now being used in Israel to verify the existence of dockerin-cohesin interactions and cellulosome production by R. albus. The Israeli partners have also conducted virtually all of the studies specific to the second Objective of the proposal. Comparative blotting studies have been conducted using specific antibodies prepare against purified recombinant cohesins and X-domains, derived from cellulosomal scaffoldins of R. flavefaciens 17, a Clostridium thermocellum mutant-preabsorbed antibody preparation, or against CbpC (fimbrial protein) of R. albus 8. The data also suggest that additional cellulolytic bacteria including Fibrobacter succinogenes S85, F. intestinalis DR7 and Butyrivibrio fibrisolvens Dl may also employ cellulosomal modules similar to those of R. flavefaciens 17. Collectively, our work during the grant period has shown that R. albus and other ruminal bacteria employ several novel mechanisms for their adhesion to plant surfaces, and produce both cellulosomal and non-cellulosomal forms of glycoside hydrolases underpinning plant fiber degradation. These improvements in our mechanistic understanding of bacterial adhesion and enzyme regulation now offers the potential to: i) optimize ruminal and hindgut conditions by dietary additives to maximize fiber degradation (e.g. by the addition of select enzymes or PAA/PPA); ii) identify plant-borne influences on adhesion and fiber-degradation, which might be overcome (or improved) by conventional breeding or transgenic plant technologies and; iii) engineer or select microbes with improved adhesion capabilities, cellulosome assembly and fiber degradation. The potential benefits associated with this research proposal are likely to be realized in the medium term (5-10 years).