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43. Oligosaccharins.

Author

Albersheim, Peter and Darvill, Alan G.

Abstract

Related history and laboratory work which lead to isolation of oligosaccharins, a new class of regulatory molecules found in plant cell walls. These substances function in growth, development, reproduction, and defense. Mixtures of oligosaccharins and other hormones can stimulate growth of an undifferentiated callus, roots, vegetative shoots/leaves, or floral shoots. (DH)

Published
1985

44. Oligosaccharins

Author

Albersheim, Peter and Darvill, Alan G.

Published
1985

45. Identification of an endo-greek small letter beta-1,4-D-Xylanase from Magnaporthe grisea by gene knockout analysis, purification and heterologous expression

Author

Sheng-Cheng Wu, Halley, Jeffrey E., Luttig, Christopher, Fernekes, Linda M., Gutierrez-Sanchez, Gerardo, Darvill, Alan G., and Albersheim; Peter

Subjects
Gene expression -- Research, Bacteriology, Agricultural -- Research, Biological sciences
Abstract

A Magnaporthe grisea knockout mutant for XYL-6, which was created showed to be as virulent as the parent strain in infecting the rice host and two endoxylanases from the parent were each purified to homogeneity. XYL-6 was introduced into Pichia pastoris for heterologous expression, which resulted in the purification of a fusion protein XYL-6H, establishing that the XYL-6 gene encodes a secreted endo-greek small letter beta-1-4-D-xylanase.

Published
2006

46. Rhamnogalacturonan II: structure and function of a borate cross-linked cell wall pectic polysaccharide

Author

O'Neill, Malcolm A., Ishii, Tadashi, Albersheim, Peter, and Darvill, Alan G.

Subjects
Borates -- Structure, Borates -- Properties, Borates -- Analysis, Plant cell walls -- Structure, Plant cell walls -- Properties, Plant cell walls -- Analysis, Pectin -- Structure, Pectin -- Properties, Pectin -- Analysis, Biological sciences, Science and technology
Abstract

Rhamnogalacturonan II (RG II) is present in the primary walls of angiosperms, gymnosperms, lycophytes, and pteridophytes. RG II is composed of at least 12 different glycosyl residues linked together by more than 20 different glycosidic linkages.

Published
2004

48. Detection of Expansin Proteins and Activity during Tomato Fruit Ontogeny1

Author

Rose, Jocelyn K.C., Cosgrove, Daniel J., Albersheim, Peter, Darvill, Alan G., and Bennett, Alan B.

Subjects
Sequence Homology, Amino Acid, Immunoblotting, food and beverages, Gene Expression Regulation, Developmental, Ethylenes, Hypocotyl, Recombinant Proteins, Solanum lycopersicum, Cell Wall, Gene Expression Regulation, Plant, Fruit, Protein Isoforms, Cucumis sativus, Research Article, Plant Proteins
Abstract

Expansins are plant proteins that have the capacity to induce extension in isolated cell walls and are thought to mediate pH-dependent cell expansion. J.K.C. Rose, H.H. Lee, and A.B. Bennett ([1997] Proc Natl Acad Sci USA 94: 5955-5960) reported the identification of an expansin gene (LeExp1) that is specifically expressed in ripening tomato (Lycopersicon esculentum) fruit where cell wall disassembly, but not cell expansion, is prominent. Expansin expression during fruit ontogeny was examined using antibodies raised to recombinant LeExp1 or a cell elongation-related expansin from cucumber (CsExp1). The LeExp1 antiserum detected expansins in extracts from ripe, but not preripe tomato fruit, in agreement with the pattern of LeExp1 mRNA accumulation. In contrast, antibodies to CsExp1 cross-reacted with expansins in early fruit development and the onset of ripening, but not at a later ripening stage. These data suggest that ripening-related and expansion-related expansin proteins have distinct antigenic epitopes despite overall high sequence identity. Expansin proteins were detected in a range of fruit species and showed considerable variation in abundance; however, appreciable levels of expansin were not present in fruit of the rin or Nr tomato mutants that exhibit delayed and reduced softening. LeExp1 protein accumulation was ethylene-regulated and matched the previously described expression of mRNA, suggesting that expression is not regulated at the level of translation. We report the first detection of expansin activity in several stages of fruit development and while characteristic creep activity was detected in young and developing tomato fruit and in ripe pear, avocado, and pepper, creep activity in ripe tomato showed qualitative differences, suggesting both hydrolytic and expansin activities.

Published
2000

49. Galactose-Depleted Xyloglucan Is Dysfunctional and Leads to Dwarfism in Arabidopsis.

Author

Yingzhen Kong, Peña, Maria J., Renna, Luciana, Avci, Utku, Pattathil, Sivakumar, Tuomivaara, Sami T., Xuemei Li, Reiter, Wolf-Dieter, Brandizzi, Federica, Hahn, Michael G., Darvill, Alan G., York, William S., and O'Neill, Malcolm A.

Subjects
XYLOGLUCANS, PLANT cells & tissues, PLANT stems, GALACTOSE, GALACTOSYLTRANSFERASE genetics
Abstract

Xyloglucan is a polysaccharide that has important roles in the formation and function of the walls that surround growing land plant cells. Many of these plants synthesize xyloglucan that contains galactose in two different side chains (L and F), which exist in distinct molecular environments. However, little is known about the contribution of these side chains to xyloglucan function. Here, we show that Arabidopsis (Arabidopsis thaliana) mutants devoid of the F side chain galactosyltransferase MURUS3 (MUR3) form xyloglucan that lacks F side chains and contains much less galactosylated xylose than its wild-type counterpart. The galactose- depleted xyloglucan is dysfunctional, as it leads to mutants that are dwarfed with curled rosette leaves, short petioles, and short in florescence stems. Moreover, cell wall matrix polysaccharides, including xyloglucan and pectin, are not properly secreted and instead accumulate within intracellular aggregates. Near-normal growth is restored by generating mur3 mutants that produce no detectable amounts of xyloglucan. Thus, cellular processes are affected more by the presence of the dysfunctional xyloglucan than by eliminating xyloglucan altogether. To identify structural features responsible for xyloglucan dysfunction, xyloglucan structure was modified in situ by generating mur3 mutants that lack specific xyloglucan xylosyltransferases (XXTs) or that overexpress the XYLOGLUCAN L-SIDE CHAIN GALACTOSYLTRANSFERASE2 (XLT2) gene. Normal growth was restored in the mur3-3 mutant overexpressing XLT2 and in mur3-3 xxt double mutants when the dysfunctional xyloglucan was modified by doubling the amounts of galactosylated side chains. Our study assigns a role for galactosylation in normal xyloglucan function and demonstrates that altering xyloglucan side chain structure disturbs diverse cellular and physiological processes. [ABSTRACT FROM AUTHOR]

Published
2015
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50. 4-0-methylation of glucuronic acid in Arabidopsis glucuronoxylan is catalyzed by a domain of unknown function family 579 protein.

Author

Urbanowicz, Breeanna R., Peña, Maria J., Ratnaparkhe, Supriya, Avci, Utku, Backe, Jason, Steet, Heather F., Foston, Marcus, Hongjia Li, 0'Neill, Malcolm A., Ragauskas, Arthur J., Darvill, Alan G., Wyman, Charles, Gilbert, Harry J., and York, William S.

Subjects
METHYLATION, GLUCURONIC acid, ARABIDOPSIS, XYLANS, HEMICELLULOSE, PLANT cell walls, METHYLTRANSFERASES, BIOSYNTHESIS
Abstract

The hemicellulose 4-O-methyl glucuronoxylan is one of the principle components present in the secondary cell walls of eudicotyledonous plants. However, the biochemical mechanisms leading to the formation of this polysaccharide and the effects of modulating its structure on the physical properties of the cell wall are poorly understood. We have identified and functionally characterized an Arabidopsis glucuronoxylan methyltransferase (GXMT) that catalyzes 4-O-methylation of the glucuronic acid substituents of this polysaccharide. AtGXMTI, which was previously classified as a domain of unknown function (DUF) 579 protein, specifically transfers the methyl group from S-adenosyl-L-methionine to 0-4 of a-D-glucopyranosyluronic acid residues that are linked to 0-2 of the xylan backbone. Biochemical characterization of the recombinant enzyme indicates that GXMT1 is localized in the Golgi apparatus and requires CO2+ for optimal activity in vitro. Plants lacking GXMT1 synthesize glucuronoxylan in which the degree of 4-O-methylation is reduced by 75%. This result is correlated to a change in lignin monomer composition and an increase in glucuronoxylan release during hydrothermal treatment of secondary cell walls. We propose that the DUF579 proteins constitute a previously undescribed family of cation-dependent, polysaccharide-specific O-methyl-transferases. This knowledge provides new opportunities to selectively manipulate polysaccharide O-methylation and extends the portfolio of structural targets that can be modified either alone or in combination to modulate biopolymer interactions in the plant cell wall. [ABSTRACT FROM AUTHOR]

Published
2012
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