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Fromm J. Xylem Development in Trees: From Cambial Divisions to Mature Wood Cells. PLANT CELL MONOGRAPHS 2013. [DOI: 10.1007/978-3-642-36491-4_1] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Kaida R, Sugawara S, Negoro K, Maki H, Hayashi T, Kaneko TS. Acceleration of cell growth by xyloglucan oligosaccharides in suspension-cultured tobacco cells. MOLECULAR PLANT 2010; 3:549-54. [PMID: 20507937 DOI: 10.1093/mp/ssq010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The incorporation of xyloglucan oligosaccharide (XXXG) into the walls of suspension-cultured tobacco cells accelerated cell expansion followed by cell division, changed cell shape from cylindrical to spherical, decreased cell size, and caused cell aggregation. Fluorescent XXXG added to the culture medium was found to be incorporated into the surface of the entire wall, where strong incorporation occurred not only on the surface, but also in the interface walls between cells during cell division. Cell expansion was always greater in the transverse direction than in the longitudinal direction and then, immediately, expansion led to cell division in the presence of XXXG; this process might result in the high level of cell aggregation seen in cultured tobacco cells. We concluded that the integration of this oligosaccharide into the walls could accelerate not only cell expansion, but also cell division in cultured cells.
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Affiliation(s)
- Rumi Kaida
- Department of Chemical and Biological Sciences, Japan Women's University, Tokyo, 112-8681, Japan
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3
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Abdeev RM, Abdeeva IA, Bruskin SS, Musiychuk KA, Goldenkova-Pavlova IV, Piruzian ES. Bacterial thermostable beta-glucanases as a tool for plant functional genomics. Gene 2009; 436:81-9. [PMID: 19393166 DOI: 10.1016/j.gene.2009.01.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Revised: 01/28/2009] [Accepted: 01/28/2009] [Indexed: 11/24/2022]
Abstract
A new strategy for creating experimental models for functional genomics has been proposed. It is based on the expression in transgenic plants of genes from thermophilic bacteria encoding functional analogues of plant proteins with high specific activity and thermal stability. We have validated this strategy by comparing physiological, biochemical and molecular properties of control tobacco plants and transgenic plants expressing genes of beta-glucanases with different substrate specificity. We demonstrate that the expression of bacterial beta-1,3-1,4-glucanase gene exerts no significant influence on tobacco plant metabolism, while the expression of bacterial beta-1,3-glucanase affects plant metabolism only at early stages of growth and development. By contrast, the expression of bacterial beta-1,4-glucanase has a significant effect on transgenic tobacco plant metabolism, namely, it affects plant morphology, the thickness of the primary cell wall, phytohormonal status, and the relative sugar content. We propose a hypothesis of beta-glucanase action as an important factor of genetic regulation of metabolic processes in plants.
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Affiliation(s)
- Rustam M Abdeev
- Center for Theoretical Problems of Physico-Chemical Pharmacology RAS, Moscow, Russia
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Bauer S, Vasu P, Mort AJ, Somerville CR. Cloning, expression, and characterization of an oligoxyloglucan reducing end-specific xyloglucanobiohydrolase from Aspergillus nidulans. Carbohydr Res 2005; 340:2590-7. [PMID: 16214120 DOI: 10.1016/j.carres.2005.09.014] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Accepted: 09/01/2005] [Indexed: 11/30/2022]
Abstract
An oligoxyloglucan reducing end-specific xyloglucanobiohydrolase from the filamentous fungus Aspergillus nidulans was cloned and expressed in Pichia pastoris as a secreted histidine-tagged protein and purified by affinity chromatography. The enzyme acts on xyloglucan oligomers and releases the first two glycosyl residue segments from the reducing end, provided that neither the first glucose nor the xylose attached to the third glucose residue from the reducing end is not further substituted. The enzyme has a specific activity of 7 U/mg at the pH optimum of 3 and at the temperature optimum of 42 degrees C.
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Affiliation(s)
- Stefan Bauer
- Carnegie Institution, Department of Plant Biology, Stanford, CA 94305, USA
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Maldonado-Mendoza IE, Dewbre GR, Blaylock L, Harrison MJ. Expression of a xyloglucan endotransglucosylase/hydrolase gene, Mt-XTH1, from Medicago truncatula is induced systemically in mycorrhizal roots. Gene 2005; 345:191-7. [PMID: 15716119 DOI: 10.1016/j.gene.2004.10.028] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Revised: 10/08/2004] [Accepted: 10/21/2004] [Indexed: 11/26/2022]
Abstract
Xyloglucan endotransglucosylase/hydrolases (XTH) are enzymes that catalyze the hydrolysis and transglycosylation of xyloglucan polymers in plant cell walls. Previously, we isolated a cDNA from mycorrhizal roots of Medicago truncatula that is predicted to encode an XTH [van Buuren, M.L., Maldonado-Mendoza, I.E., Trieu, A.T., Blaylock, L.A., Harrison, M.J., 1999. Novel genes induced during an arbuscular mycorrhizal (AM) symbiosis between M. truncatula and G. versiforme. Mol. Plant-Microb. Interact. 12, 171-181.]. Here, we identified the corresponding XTH gene, designated Mt-XTH1. The Mt-XTH1 gene contains four exons separated by three introns and resides on a 15-kb Xba1 fragment adjacent to a second XTH gene designated Mt-XTH2. Mt-XTH2 shares the same exon-intron structure as Mt-XTH1. Exons 2, 3 and 4 and introns 1 and 2 are identical to Mt-XTH1, while exon 1 and intron 3 are divergent, both in sequence and in length. Mt-XTH1 is induced following colonization of the roots by AM fungi but does not respond to changes in phosphate status. Analysis of transgenic roots expressing an Mt-XTH1 promoterColon, two colonsuidA fusion revealed that the Mt-XTH1 promoter directs expression in cells throughout the root system with significantly higher levels of activity in mycorrhizal roots. Mt-XTH1 expression is elevated not only in the regions of the roots colonized by the fungus, but also at sites distal to the infected regions. These expression patterns are consistent with activation in response to a systemic signal.
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Park YW, Baba K, Furuta Y, Iida I, Sameshima K, Arai M, Hayashi T. Enhancement of growth and cellulose accumulation by overexpression of xyloglucanase in poplar. FEBS Lett 2004; 564:183-7. [PMID: 15094064 DOI: 10.1016/s0014-5793(04)00346-1] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2004] [Revised: 03/19/2004] [Accepted: 03/19/2004] [Indexed: 10/26/2022]
Abstract
Because the loosening of xyloglucan in the cell wall promotes plant growth (Takeda et al. (2002) Proc. Natl. Acad. Sci. USA 99, 9055-9060; Park et al. (2003) Plant J. 33, 1099-1106), we expressed Aspergillus xyloglucanase constitutively in Populus alba. The expression increased the length of stem even in the presence of sucrose. Increased stem growth was accompanied by a decrease in Young's elastic modulus in the growth zone but an increased elasticity in mature tissue. The increased internode length corresponded to an increase in cellulose content as well as specific gravity, showing that the removal of xyloglucan might cause an increase in cellulose density in the secondary xylem.
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Affiliation(s)
- Yong Woo Park
- Wood Research Institute, Kyoto University, Gokasho, Uji 611-0011, Japan
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Fry SC. Primary cell wall metabolism: tracking the careers of wall polymers in living plant cells. THE NEW PHYTOLOGIST 2004; 161:641-675. [PMID: 33873719 DOI: 10.1111/j.1469-8137.2004.00980.x] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Numerous examples have been presented of enzyme activities, assayed in vitro, that appear relevant to the synthesis of structural polysaccharides, and to their assembly and subsequent degradation in the primary cell walls (PCWs) of higher plants. The accumulation of the corresponding mRNAs, and of the (immunologically recognized) proteins, has often also (or instead) been reported. However, the presence of these mRNAs, antigens and enzymic activities has rarely been shown to correspond to enzyme action in the living plant cell. In some cases, apparent enzymic action is observed in vivo for which no enzyme activity can be detected in in-vitro assays; the converse also occurs. Methods are reviewed by which reactions involving structural wall polysaccharides can be tracked in vivo. Special attention is given to xyloglucan endotransglucosylase (XET), one of the two enzymic activities exhibited in vitro by xyloglucan endotransglucosylase/hydrolase (XTH) proteins, because of its probable importance in the construction and restructuring of the PCW's major hemicellulose. Attention is also given to the possibility that some reactions observed in the PCW in vivo are not directly enzymic, possibly involving the action of hydroxyl radicals. It is concluded that some proposed wall enzymes, for example XTHs, do act in vivo, but that for other enzymes this is not proven. Contents I. Primary cell walls: composition, deposition and roles 642 II. Reactions that have been proposed to occur in primary cell walls 645 III. Tracking the careers of wall components in vivo: evidence for action of enzymes in the walls of living plant cells 656 IV. Evidence for the occurrence of nonenzymic polymer scission in vivo? 666 VI. Conclusion 667 References 667.
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Affiliation(s)
- Stephen C Fry
- The Edinburgh Cell Wall Group, Institute of Cell and Molecular Biology, The University of Edinburgh, Daniel Rutherford Building, The King's Buildings, Mayfield Road, Edinburgh EH9 3JH, UK
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Kaku T, Tabuchi A, Wakabayashi K, Hoson T. Xyloglucan oligosaccharides cause cell wall loosening by enhancing xyloglucan endotransglucosylase/hydrolase activity in azuki bean epicotyls. PLANT & CELL PHYSIOLOGY 2004; 45:77-82. [PMID: 14749488 DOI: 10.1093/pcp/pch007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Addition of xyloglucan-derived oligosaccharides shifted the wall-bound xyloglucans to a lower molecular mass distribution and increased the cell wall extensibility of the native epidermal tissue strips isolated from azuki bean (Vigna angularis) epicotyls. To ascertain the mechanism of oligosaccharide function, we examined the action of a xyloglucan endotransglucosylase/hydrolase (XTH) showing both endotransglucosylase and endohydrolase activities, isolated from azuki bean epicotyl cell walls, in the presence of xyloglucan oligosaccharides. The addition of xyloglucan oligosaccharides enhanced the xyloglucan-degrading activity of XTH against isolated xyloglucan substrates. When the methanol-fixed epidermal tissue strips were incubated with XTH, the molecular mass of wall-bound xyloglucans was decreased and the cell wall extensibility increased markedly in the presence of the oligosaccharides. These results suggest that xyloglucan oligosaccharides stimulate the degradation of xyloglucans by enhancing the XTH activity within the cell wall architecture, thereby increasing the cell wall extensibility in azuki bean epicotyls.
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Affiliation(s)
- Tomomi Kaku
- Department of Biological Sciences, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, 558-8585 Japan
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Hager A. Role of the plasma membrane H+-ATPase in auxin-induced elongation growth: historical and new aspects. JOURNAL OF PLANT RESEARCH 2003; 116:483-505. [PMID: 12937999 DOI: 10.1007/s10265-003-0110-x] [Citation(s) in RCA: 227] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2003] [Accepted: 03/27/2003] [Indexed: 05/17/2023]
Abstract
This article will cover historical and recent aspects of reactions and mechanisms involved in the auxin-induced signalling cascade that terminates in the dramatic elongation growth of cells and plant organs. Massive evidence has accumulated that the final target of auxin action is the plasma membrane H(+)-ATPase, which excretes H(+) ions into the cell wall compartment and, in an antiport, takes up K(+) ions through an inwardly rectifying K(+) channel. The auxin-enhanced H(+) pumping lowers the cell wall pH, activates pH-sensitive enzymes and proteins within the wall, and initiates cell-wall loosening and extension growth. These processes, induced by auxin or by the "super-auxin" fusicoccin, can be blocked instantly and specifically by a voltage inhibition of the H(+)-ATPase due to removal of K(+) ions or the addition of K(+)-channel blockers. Vice versa, H(+) pumping and growth are immediately switched on by addition of K(+) ions. Furthermore, the treatment of segments either with auxin or with fusicoccin (which activates the H(+)-ATPase irreversibly) or with acid buffers (from outside) causes an identical transformation and degradation pattern of cell wall constituents during cell-wall loosening and growth. These and other results described below are in agreement with the acid-growth theory of elongation growth. However, objections to this theory are also discussed.
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Affiliation(s)
- Achim Hager
- Botanisches Institut, Universität Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany
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Suda CNK, Giorgini JF. Multiple forms of endo-1,4-beta-glucanases in the endosperm of Euphorbia heterophylla L. JOURNAL OF EXPERIMENTAL BOTANY 2003; 54:2045-2052. [PMID: 12885862 DOI: 10.1093/jxb/erg229] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Germinating seeds of Euphorbia heterophylla L. contain endo-1,4-beta-glucanases which degrade carboxymethylcellulose (CMC). The activity decreased approximately 66% in extracts of endosperm containing isopropanol or ethanol. The endoglucanases were isolated from endosperm extracts using ammonium sulphate fractionation followed by Sephacryl S-100-HR chromatography resulting in two main peaks: I and II. Peak I endoglucanase was further purified about 15-fold on DEAE-Sephadex A50 and then by affinity chromatography (CF11-cellulose). Peak II endoglucanases were further purified 10-fold on CM-cellulose chromatography. The results indicated the occurrence of a 66 kDa endoglucanase (fractionated by SDS-PAGE and visualized by activity staining using Congo Red). Several acidic (pI 3.0 to 5.7) and basic (pI 8.5 to 10.0) forms from both peaks which differed in their capacities for degrading CMC or xyloglucans from Copaifera langsdorffii or Hymenaea courbaril were detected.
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Affiliation(s)
- Cecilia N K Suda
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, 14049-900, Brazil
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Hyodo H, Yamakawa S, Takeda Y, Tsuduki M, Yokota A, Nishitani K, Kohchi T. Active gene expression of a xyloglucan endotransglucosylase/hydrolase gene, XTH9, in inflorescence apices is related to cell elongation in Arabidopsis thaliana. PLANT MOLECULAR BIOLOGY 2003; 52:473-82. [PMID: 12856951 DOI: 10.1023/a:1023904217641] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Regulation of cell wall structure plays a central role in growth and differentiation in plants. Xyloglucan endotransglucosylase/hydrolases (XTHs) that catalyze the cleavage and molecular grafting of xyloglucan chains function in loosening and rearrangement of the cell wall. We have characterized XTH9, a member of the XTH family that was isolated by systematic differential screening for highly expressed genes in shoot apices in Arabidopsis. In the vegetative phase, XTH9 transcripts accumulate in the shoot apex region. In the reproductive phase, transcript levels in shoot apices increase further, and they also are detected in flower buds, flower stalks and internodes bearing flowers. XTH9 expression levels were reduced markedly in mutants such as acl which are characterized by short internodal cell lengths, but recover at permissive temperatures in the temperature-sensitive acl mutants. Differential expression of XTH9 along the inflorescence stem was also detected in pin1 where no lateral organs are formed. These observations suggest that XTH9 expression is coordinated with plant development, including the differentiation from vegetative and reproductive meristems and cell elongation of the inflorescence stem.
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Affiliation(s)
- Hideki Hyodo
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
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Rose JKC, Braam J, Fry SC, Nishitani K. The XTH family of enzymes involved in xyloglucan endotransglucosylation and endohydrolysis: current perspectives and a new unifying nomenclature. PLANT & CELL PHYSIOLOGY 2002; 43:1421-35. [PMID: 12514239 DOI: 10.1093/pcp/pcf171] [Citation(s) in RCA: 474] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
The polysaccharide xyloglucan is thought to play an important structural role in the primary cell wall of dicotyledons. Accordingly, there is considerable interest in understanding the biochemical basis and regulation of xyloglucan metabolism, and research over the last 16 years has identified a large family of cell wall proteins that specifically catalyze xyloglucan endohydrolysis and/or endotransglucosylation. However, a confusing and contradictory series of nomenclatures has emerged in the literature, of which xyloglucan endotransglycosylases (XETs) and endoxyloglucan transferases (EXGTs) are just two examples, to describe members of essentially the same class of genes/proteins. The completion of the first plant genome sequencing projects has revealed the full extent of this gene family and so this is an opportune time to resolve the many discrepancies in the database that include different names being assigned to the same gene. Following consultation with members of the scientific community involved in plant cell wall research, we propose a new unifying nomenclature that conveys an accurate description of the spectrum of biochemical activities that cumulative research has shown are catalyzed by these enzymes. Thus, a member of this class of genes/proteins will be referred to as a xyloglucan endotransglucosylase/hydrolase (XTH). The two known activities of XTH proteins are referred to enzymologically as xyloglucan endotransglucosylase (XET, which is hereby re-defined) activity and xyloglucan endohydrolase (XEH) activity. This review provides a summary of the biochemical and functional diversity of XTHs, including an overview of the structure and organization of the Arabidopsis XTH gene family, and highlights the potentially important roles that XTHs appear to play in numerous examples of plant growth and development.
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Affiliation(s)
- Jocelyn K C Rose
- Department of Plant Biology, 228 Plant Science Building, Cornell University, Ithaca, NY 14853, USA.
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Harpster MH, Dawson DM, Nevins DJ, Dunsmuir P, Brummell DA. Constitutive overexpression of a ripening-related pepper endo-1,4-beta-glucanase in transgenic tomato fruit does not increase xyloglucan depolymerization or fruit softening. PLANT MOLECULAR BIOLOGY 2002; 50:357-369. [PMID: 12369613 DOI: 10.1023/a:1019888129013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The ripening-related pepper endo-1,4-beta-D-glucanase (EGase) CaCel1 was over-expressed in transgenic tomato plants under the control of the constitutive 35S promoter to investigate the effects on plant growth and fruit softening of high levels of a potential cell wall-degrading activity. In transgenic fruit, recombinant CaCel1 protein was associated with a high-salt putative cell wall fraction, and extractable CMCase activity was increased by up to 20-fold relative to controls. However, the effects of high levels of EGase activity on fruit cell wall metabolism were relatively small. The largest consequence observed was a decrease of up to 20% in the amount of matrix glycans in a 24% KOH-soluble fraction consisting of polysaccharides tightly bound to cellulose. This decrease was confined to polysaccharides other than xyloglucan, did not affect the size distribution of remaining molecules, and was not correlated with a corresponding increase in glycans in a 4% KOH-soluble fraction loosely bound to cellulose, suggesting that the missing polymers had been degraded to fragments small enough to be lost from the extracts. The amount of matrix glycans in the 4% KOH-soluble fraction was not substantially changed, but the size distribution showed a small relative increase in the amount of polymers in a peak eluting close to a linear dextran marker of 71 kDa. This could be due either to an increase in the amount of polymers of this size, or to a loss from the extract of other polymers present in peaks of higher molecular weight. Transgenic fruit were not softer than controls but appeared the same or slightly firmer at both green and red developmental stages, and no differences in plant vegetative growth were observed. CaCel1 did not cause depolymerization of tomato fruit xyloglucan in vivo, but differences in the amount or molecular weight profile of other matrix glycans were observed. The data suggest that degradation of a proportion of matrix glycans other than xyloglucan does not result in fruit softening, and that fruit softening is not limited by the amount of EGase activity present during ripening.
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Takeda T, Furuta Y, Awano T, Mizuno K, Mitsuishi Y, Hayashi T. Suppression and acceleration of cell elongation by integration of xyloglucans in pea stem segments. Proc Natl Acad Sci U S A 2002; 99:9055-60. [PMID: 12084943 PMCID: PMC124422 DOI: 10.1073/pnas.132080299] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2002] [Indexed: 11/18/2022] Open
Abstract
Xyloglucan is a key polymer in the walls of growing plant cells. Using split pea stem segments and stem segments from which the epidermis had been peeled off, we demonstrate that the integration of xyloglucan mediated by the action of wall-bound xyloglucan endotransglycosylase suppressed cell elongation, whereas that of its fragment oligosaccharide accelerated it. Whole xyloglucan was incorporated into the cell wall and induced the rearrangement of cortical microtubules from transverse to longitudinal; in contrast, the oligosaccharide solubilized xyloglucan from the cell wall and maintained the microtubules in a transverse orientation. This paper proposes that xyloglucan metabolism controls the elongation of plant cells.
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Affiliation(s)
- Takumi Takeda
- Wood Research Institute, Kyoto University, Gokasho, Uji 611-0011, Japan
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Mellerowicz EJ, Baucher M, Sundberg B, Boerjan W. Unravelling cell wall formation in the woody dicot stem. PLANT MOLECULAR BIOLOGY 2001; 47:239-274. [PMID: 11554475 DOI: 10.1023/a:1010699919325] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Populus is presented as a model system for the study of wood formation (xylogenesis). The formation of wood (secondary xylem) is an ordered developmental process involving cell division, cell expansion, secondary wall deposition, lignification and programmed cell death. Because wood is formed in a variable environment and subject to developmental control, xylem cells are produced that differ in size, shape, cell wall structure, texture and composition. Hormones mediate some of the variability observed and control the process of xylogenesis. High-resolution analysis of auxin distribution across cambial region tissues, combined with the analysis of transgenic plants with modified auxin distribution, suggests that auxin provides positional information for the exit of cells from the meristem and probably also for the duration of cell expansion. Poplar sequencing projects have provided access to genes involved in cell wall formation. Genes involved in the biosynthesis of the carbohydrate skeleton of the cell wall are briefly reviewed. Most progress has been made in characterizing pectin methyl esterases that modify pectins in the cambial region. Specific expression patterns have also been found for expansins, xyloglucan endotransglycosylases and cellulose synthases, pointing to their role in wood cell wall formation and modification. Finally, by studying transgenic plants modified in various steps of the monolignol biosynthetic pathway and by localizing the expression of various enzymes, new insight into the lignin biosynthesis in planta has been gained.
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Affiliation(s)
- E J Mellerowicz
- Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå
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Brummell DA, Harpster MH. Cell wall metabolism in fruit softening and quality and its manipulation in transgenic plants. PLANT MOLECULAR BIOLOGY 2001; 47:311-340. [PMID: 11554479 DOI: 10.1023/a:1010656104304] [Citation(s) in RCA: 487] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Excessive softening is the main factor limiting fruit shelf life and storage. Transgenic plants modified in the expression of cell wall modifying proteins have been used to investigate the role of particular activities in fruit softening during ripening, and in the manufacture of processed fruit products. Transgenic experiments show that polygalacturonase (PG) activity is largely responsible for pectin depolymerization and solubilization, but that PG-mediated pectin depolymerization requires pectin to be de-methyl-esterified by pectin methylesterase (PME), and that the PG beta-subunit protein plays a role in limiting pectin solubilization. Suppression of PG activity only slightly reduces fruit softening (but extends fruit shelf life), suppression of PME activity does not affect firmness during normal ripening, and suppression of beta-subunit protein accumulation increases softening. All these pectin-modifying proteins affect the integrity of the middle lamella, which controls cell-to-cell adhesion and thus influences fruit texture. Diminished accumulation of either PG or PME activity considerably increases the viscosity of tomato juice or paste, which is correlated with reduced polyuronide depolymerization during processing. In contrast, suppression of beta-galactosidase activity early in ripening significantly reduces fruit softening, suggesting that the removal of pectic galactan side-chains is an important factor in the cell wall changes leading to ripening-related firmness loss. Suppression or overexpression of endo-(1-->4)beta-D-glucanase activity has no detectable effect on fruit softening or the depolymerization of matrix glycans, and neither the substrate nor the function for this enzyme has been determined. The role of xyloglucan endotransglycosylase activity in softening is also obscure, and the activity responsible for xyloglucan depolymerization during ripening, a major contributor to softening, has not yet been identified. However, ripening-related expansin protein abundance is directly correlated with fruit softening and has additional indirect effects on pectin depolymerization, showing that this protein is intimately involved in the softening process. Transgenic work has shown that the cell wall changes leading to fruit softening and textural changes are complex, and involve the coordinated and interdependent activities of a range of cell wall-modifying proteins. It is suggested that the cell wall changes caused early in ripening by the activities of some enzymes, notably beta-galactosidase and ripening-related expansin, may restrict or control the activities of other ripening-related enzymes necessary for the fruit softening process.
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Mellerowicz EJ, Baucher M, Sundberg B, Boerjan W. Unravelling cell wall formation in the woody dicot stem. PLANT MOLECULAR BIOLOGY 2001; 47:239-274. [PMID: 11554475 DOI: 10.1007/978-94-010-0668-2_15] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Populus is presented as a model system for the study of wood formation (xylogenesis). The formation of wood (secondary xylem) is an ordered developmental process involving cell division, cell expansion, secondary wall deposition, lignification and programmed cell death. Because wood is formed in a variable environment and subject to developmental control, xylem cells are produced that differ in size, shape, cell wall structure, texture and composition. Hormones mediate some of the variability observed and control the process of xylogenesis. High-resolution analysis of auxin distribution across cambial region tissues, combined with the analysis of transgenic plants with modified auxin distribution, suggests that auxin provides positional information for the exit of cells from the meristem and probably also for the duration of cell expansion. Poplar sequencing projects have provided access to genes involved in cell wall formation. Genes involved in the biosynthesis of the carbohydrate skeleton of the cell wall are briefly reviewed. Most progress has been made in characterizing pectin methyl esterases that modify pectins in the cambial region. Specific expression patterns have also been found for expansins, xyloglucan endotransglycosylases and cellulose synthases, pointing to their role in wood cell wall formation and modification. Finally, by studying transgenic plants modified in various steps of the monolignol biosynthetic pathway and by localizing the expression of various enzymes, new insight into the lignin biosynthesis in planta has been gained.
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Affiliation(s)
- E J Mellerowicz
- Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå
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Yuan S, Wu Y, Cosgrove DJ. A fungal endoglucanase with plant cell wall extension activity. PLANT PHYSIOLOGY 2001; 127:324-33. [PMID: 11553760 PMCID: PMC117988 DOI: 10.1104/pp.127.1.324] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2001] [Revised: 05/07/2001] [Accepted: 06/01/2001] [Indexed: 05/18/2023]
Abstract
We have identified a wall hydrolytic enzyme from Trichoderma reesei with potent ability to induce extension of heat-inactivated type I cell walls. It is a small (23-kD) endo-1,4-beta-glucanase (Cel12A) belonging to glycoside hydrolase family 12. Extension of heat-inactivated walls from cucumber (Cucumis sativus cv Burpee Pickler) hypocotyls was induced by Cel12A after a distinct lag time and was accompanied by a large increase in wall plasticity and elasticity. Cel12A also increased the rate of stress relaxation of isolated walls at very short times (<200 ms; equivalent to reducing t(0), a parameter that estimates the minimum relaxation time). Similar changes in wall plasticity and elasticity were observed in wheat (Triticum aestivum cv Pennmore Winter) coleoptile (type II) walls, which showed only a negligible extension in response to Cel12A treatment. Thus, Cel12A modifies both type I and II walls, but substantial extension is found only in type I walls. Cel12A has strong endo-glucanase activity against xyloglucan and (1-->3,1-->4)-beta-glucan, but did not exhibit endo-xylanase, endo-mannase, or endo-galactanase activities. In terms of kinetics of action and effects on wall rheology, wall loosening by Cel12A differs qualitatively from the action by expansins, which induce wall extension by a non-hydrolytic polymer creep mechanism. The action by Cel12A mimics some of the changes in wall rheology found after auxin-induced growth. The strategy used here to identify Cel12A could be used to identify analogous plant enzymes that cause auxin-induced changes in cell wall rheology.
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Affiliation(s)
- S Yuan
- Department of Biology, 208 Mueller Lab, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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19
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Brummell DA, Harpster MH. Cell wall metabolism in fruit softening and quality and its manipulation in transgenic plants. PLANT MOLECULAR BIOLOGY 2001. [PMID: 11554479 DOI: 10.1007/978-94-010-0668-2-18] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Excessive softening is the main factor limiting fruit shelf life and storage. Transgenic plants modified in the expression of cell wall modifying proteins have been used to investigate the role of particular activities in fruit softening during ripening, and in the manufacture of processed fruit products. Transgenic experiments show that polygalacturonase (PG) activity is largely responsible for pectin depolymerization and solubilization, but that PG-mediated pectin depolymerization requires pectin to be de-methyl-esterified by pectin methylesterase (PME), and that the PG beta-subunit protein plays a role in limiting pectin solubilization. Suppression of PG activity only slightly reduces fruit softening (but extends fruit shelf life), suppression of PME activity does not affect firmness during normal ripening, and suppression of beta-subunit protein accumulation increases softening. All these pectin-modifying proteins affect the integrity of the middle lamella, which controls cell-to-cell adhesion and thus influences fruit texture. Diminished accumulation of either PG or PME activity considerably increases the viscosity of tomato juice or paste, which is correlated with reduced polyuronide depolymerization during processing. In contrast, suppression of beta-galactosidase activity early in ripening significantly reduces fruit softening, suggesting that the removal of pectic galactan side-chains is an important factor in the cell wall changes leading to ripening-related firmness loss. Suppression or overexpression of endo-(1-->4)beta-D-glucanase activity has no detectable effect on fruit softening or the depolymerization of matrix glycans, and neither the substrate nor the function for this enzyme has been determined. The role of xyloglucan endotransglycosylase activity in softening is also obscure, and the activity responsible for xyloglucan depolymerization during ripening, a major contributor to softening, has not yet been identified. However, ripening-related expansin protein abundance is directly correlated with fruit softening and has additional indirect effects on pectin depolymerization, showing that this protein is intimately involved in the softening process. Transgenic work has shown that the cell wall changes leading to fruit softening and textural changes are complex, and involve the coordinated and interdependent activities of a range of cell wall-modifying proteins. It is suggested that the cell wall changes caused early in ripening by the activities of some enzymes, notably beta-galactosidase and ripening-related expansin, may restrict or control the activities of other ripening-related enzymes necessary for the fruit softening process.
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Thompson JE, Fry SC. Restructuring of wall-bound xyloglucan by transglycosylation in living plant cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2001; 26:23-34. [PMID: 11359607 DOI: 10.1046/j.1365-313x.2001.01005.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Xyloglucan endotransglycosylases (XETs) cleave and then re-join xyloglucan chains and may thus contribute to both wall-assembly and wall-loosening. The present experiments demonstrate the simultaneous occurrence in vivo of two types of interpolymeric transglycosylation: "integrational" (in which a newly secreted xyloglucan reacts with a previously wall-bound one) and "restructuring" (in which one previously wall-bound xyloglucan reacts with another). Xyloglucans synthesised by cultured rose (Rosa sp.) cells in "heavy" or "light" media (with [13C,2H]glucose or [12C,1H]glucose, respectively) had buoyant densities of 1.643 and 1.585 g ml-1, respectively, estimated by isopycnic centrifugation in caesium trifluoroacetate. To detect transglycosylation, we shifted heavy rose cells into light medium, then supplied a 2-h pulse of L-[1-3H]arabinose. Light [3H]xyloglucans were thus secreted into heavy, non-radioactive walls and chased by light, non-radioactive xyloglucans. At 2 h after the start of radiolabelling, the (neutral) [3H]xyloglucans were on average 29% heavy, indicating molecular grafting during integrational transglycosylation. The [3H]xyloglucans then gradually increased in density until, by 11 h, they were 38% heavy. This density increase suggests that restructuring transglycosylation reactions occurred between the now wall-bound [3H]xyloglucan and other (mainly older, i.e. heavy) wall-bound non-radioactive xyloglucans. Brefeldin A (BFA), which blocked xyloglucan secretion, did not prevent the increase in density of wall-bound [3H]xyloglucan (2-11 h). This confirms that restructuring transglycosylation occurred between pairs of previously wall-bound xyloglucans. After 7 d in BFA, the 3H was in hybrid xyloglucans in which on average 55% of the molecule was heavy. Exogenous xyloglucan oligosaccharides (competing acceptor substrates for XETs) did not affect integrational transglycosylation whereas they inhibited restructuring transglycosylation. Possible reasons for this difference are discussed. This is the first experimental evidence for restructuring transglycosylation in vivo. We argue that both integrational and restructuring transglycosylation can contribute to both wall-assembly and -loosening.
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Affiliation(s)
- J E Thompson
- The Edinburgh Cell Wall Group, Institute of Cell and Molecular Biology, The University of Edinburgh, Daniel Rutherford Building, The King's Buildings, Mayfield Road, Edinburgh EH9 3JH, UK
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Pilatzke-Wunderlich I, Nessler CL. Expression and activity of cell-wall-degrading enzymes in the latex of opium poppy, Papaver somniferum L. PLANT MOLECULAR BIOLOGY 2001; 45:567-76. [PMID: 11414615 DOI: 10.1023/a:1010624218855] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The alkaloid-rich latex of the opium poppy, Papaver somniferum L., is valued as a source of pharmaceuticals including thebaine, codeine, and morphine, but is also harvested for heroin production. The poppy laticifer system develops through the gradual disappearance of the common walls between differentiating laticifer elements throughout the plant. Gene homologues for cell-wall-degrading enzymes were found during random sequencing of an opium poppy latex cDNA library. RNA gel blot analysis of cellulase, polygalacturonase beta-subunit, 1,3-beta-glucanase, and xyloglucan endotransglycosylase homologues showed their expression was not limited to laticifers. In contrast, poppy gene homologues to pectin methylesterase (PME), pectin acetylesterase (PAE) and pectate lyase (PL) where all highly expressed and latex-specific. Enzyme assays confirmed the presence of PME, PAE, and PL activities in latex serum. The abundance of transcripts encoding pectin-degrading enzymes in latex suggests that these enzymes may play an important role in laticifer development.
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Tabuchi A, Mori H, Kamisaka S, Hoson T. A new type of endo-xyloglucan transferase devoted to xyloglucan hydrolysis in the cell wall of azuki bean epicotyls. PLANT & CELL PHYSIOLOGY 2001; 42:154-61. [PMID: 11230569 DOI: 10.1093/pcp/pce016] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
A new type of xyloglucan-degrading enzyme was isolated from the cell wall of azuki bean (Vigna angularis Ohwi et Ohashi cv. Takara) epicotyls and its characteristics were determined. The enzyme was purified to apparent homogeneity by Concanavalin A (Con A)-Sepharose, cation exchange, and gel filtration columns from a cell wall protein fraction extracted with 1 M sodium chloride. The purified enzyme gave a single protein band of 33 kDa on SDS-PAGE. The enzyme specifically cleaved xyloglucans and showed maximum activity at pH 5.0 when assayed by the iodine-staining method. An increase in reducing power in xyloglucan solution was clearly detected after treatment with the purified enzyme. Xyloglucans with molecular masses of 500 and 25 kDa were gradually hydrolyzed to 5 kDa for 96 h without production of any oligo- or monosaccharide with the purified enzyme. The purified enzyme did not show an endo-type transglycosylation reaction, even in the presence of xyloglucan oligosaccharides. Partial amino acid sequences of the enzyme shared an identity with endo-xyloglucan transferase (EXGT) family, especially with xyloglucan endotransglycosylase (XET) from nasturtium. These results suggest that the enzyme is a new member of EXGT devoted solely to xyloglucan hydrolysis.
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Affiliation(s)
- A Tabuchi
- Department of Biology, Faculty of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka, 558-8585 Japan
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Ohmiya Y, Samejima M, Shiroishi M, Amano Y, Kanda T, Sakai F, Hayashi T. Evidence that endo-1,4-beta-glucanases act on cellulose in suspension-cultured poplar cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2000; 24:147-58. [PMID: 11069690 DOI: 10.1046/j.1365-313x.2000.00860.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Suspension-cultured poplar (Populus alba) cells produce two distinct endo-1,4-beta-glucanases, one of which is released in the extracellular culture medium and the other localized in their walls. Two cDNA clones, PopCel1 and PopCel2, isolated from a poplar cDNA library, encode the extracellular and the wall-bound endo-1, 4-beta-glucanases, respectively, based upon deduced amino acid sequences. The products of these two genes contained domains conserved in endo-1,4-beta-glucanase (family 9) and showed 91.5% amino acid identity. The levels of both PopCel1 and PopCel2 mRNAs increased during the lag phase of growth and decreased rapidly during the linear phase. After the levels had decreased, they were again increased by addition of sucrose to the culture medium and further enhanced by the addition of 2,4-dichlorophenoxyacetic acid (2,4-D) in the presence of sucrose. The accumulation of the mRNAs was correlated with the solubilization of cello-oligosaccharides. Cello-oligosaccharides and xyloglucan were also solubilized from the wall preparations of poplar cells incubated with enzyme preparations from the extracellular culture medium and walls. An antibody against both PopCel proteins reduced the production of cello-oligosaccharides by the extracellular enzyme by 90% and that by the wall-bound enzyme by 55%, and also prevented xyloglucan solubilization. The results show that the accumulation of poplar endo-1,4-beta-glucanases is regulated indirectly by auxin in the presence of sucrose and can act on cellulose in suspension-cultured poplar cells.
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Affiliation(s)
- Y Ohmiya
- Wood Research Institute, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
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Picard C, Gruza J, Derouet C, Renard CM, Mazeau K, Koca J, Imberty A, Hervé Du Penhoat C. A conformational study of the xyloglucan oligomer, XXXG, by NMR spectroscopy and molecular modeling. Biopolymers 2000; 54:11-26. [PMID: 10799977 DOI: 10.1002/(sici)1097-0282(200007)54:1<11::aid-bip20>3.0.co;2-d] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A structural study of the XXXG xyloglucan heptasaccharide (X = alpha-D-Xylp(1 --> 6)-beta-D-Glcp and G = beta-D-Glcp) isolated from apple fruit has been undertaken with nmr and molecular mechanics methods. Quantitative 400 MHz nmr data including nuclear Overhauser effect spectroscopy (NOESY) volumes were recorded at both 6 and 20 degrees C. In spite of severe overlapping of resonances, it was possible to estimate summed NOEs for the majority of the anomeric and glucosyl methylene protons. An ensemble-average population of preferred geometries has been established with the CICADA conformational searching algorithm associated with the MM3 force field. Comparison of the theoretical data obtained by back-calculation of the NOESY volumes from the ensemble-average distance matrix program and motional models based on the Stokes-Einstein-Debye relation satisfactorily reproduce the experimental data. Conformational averaging about the mainchain glycosidic linkages includes both the syn and anti conformers and a minor gauche-gauche population is highly probable. The theoretical data overestimate the syn preference of the Glc(c) --> Glc(b) linkage as well as the Glc(c) GT rotamer population. Finally, both the motional models and the conformational search indicate a fairly rigid backbone and greater flexiblity for the xylose side chains.
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Affiliation(s)
- C Picard
- Département de Chimie, URA 1679, Ecole Normale Supérieure, 24 Rue Lhomond, 75231 Paris Cedex 05, France
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Trainotti L, Spolaore S, Pavanello A, Baldan B, Casadoro G. A novel E-type endo-beta-1,4-glucanase with a putative cellulose-binding domain is highly expressed in ripening strawberry fruits. PLANT MOLECULAR BIOLOGY 1999; 40:323-32. [PMID: 10412910 DOI: 10.1023/a:1006299821980] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Two full-length cDNA clones (faEG1 and faEG3, respectively) have been isolated by screening a cDNA library representing transcripts from red strawberry fruits. Southern blot analysis of genomic DNA suggests that the strawberry endo-beta-1,4-glucanases (EGases) are encoded by a multigene family. The cognate genes are predominantly expressed during the ripening process proper, although, in the case of faEG3, some expression has also been observed in large green fruits and, at low amounts, in young vegetative green tissues. In agreement with other ripening-related genes in strawberry, also the expression of faEG1 and faEG3 is down-regulated by treatment with an auxin analogue (1-naphthaleneacetic acid, NAA). Differences in temporal expression of the two EGase genes in fruits are not accompanied by differences in spatial expression. The pattern of expression and the sequence characteristics of the two polypeptides suggest that the two strawberry EGases operate in a synergistic and coordinate manner. The protein encoded by faEG1 looks like one of the usual higher-plant EGases (average molecular mass of 54 kDa), while the protein encoded by faEG3 has a greater deduced molecular mass (about 68 kDa) due to the presence of an extra peptide of about 130 amino acids at the C-terminus. Such unusual peptide shows some features also found in microbial cellulases and contains a putative cellulose-binding domain. We propose that the faEG3-encoded EGase might especially hydrolyse the xyloglucans coating the cellulose microfibrils, thus rendering the cell wall more susceptible to the subsequent hydrolytic activity of the faEG1-encoded EGase.
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Affiliation(s)
- L Trainotti
- Dipartimento di Biologia, Università di Padova, Italy
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Tominaga, Samejima, Sakai, Hayashi. Occurrence of cello-oligosaccharides in the apoplast of auxin-treated pea stems. PLANT PHYSIOLOGY 1999; 119:249-54. [PMID: 9880367 PMCID: PMC32227 DOI: 10.1104/pp.119.1.249] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/1998] [Accepted: 10/13/1998] [Indexed: 05/22/2023]
Abstract
Treatment of pea (Pisum sativum L.) hypocotyl segments with indole-3-butyric acid, which promotes segment elongation, increased the solubilization of both xyloglucan and cello-oligosaccharides in the apoplast of auxin-treated pea stems. The cello-oligosaccharides were isolated from the apoplastic solution with a charcoal/Celite column and were identified as cellobiose, cellotriose, and cellotetraose after subsequent thin-layer chromatography and paper electrophoresis. Cello-oligosaccharides in the apoplastic fraction were monitored using cellobiose dehydrogenase. Both xyloglucan and cello-oligosaccharides appeared to be formed concurrently within 30 min after treatment with the auxin, and the cello-oligosaccharides increased with stem elongation even after 2 h. The total activity of cellulase did not increase for up to 4 h.
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Affiliation(s)
- Tominaga
- Wood Research Institute, Kyoto University, Gokasho Uji, Kyoto 611, Japan (R.T., F.S., T.H.)
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27
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Pauly M, Andersen LN, Kauppinen S, Kofod LV, York WS, Albersheim P, Darvill A. A xyloglucan-specific endo-beta-1,4-glucanase from Aspergillus aculeatus: expression cloning in yeast, purification and characterization of the recombinant enzyme. Glycobiology 1999; 9:93-100. [PMID: 9884411 DOI: 10.1093/glycob/9.1.93] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A full-length c-DNA encoding a xyloglucan-specific endo -beta-1, 4-glucanase (XEG) has been isolated from the filamentous fungus Aspergillus aculeatus by expression cloning in yeast. The colonies expressing functional XEG were identified on agar plates containing azurine-dyed cross-linked xyloglucan. The cDNA encoding XEG was isolated, sequenced, cloned into an Aspergillus expression vector, and transformed into Aspergillus oryzae for heterologous expression. The recombinant enzyme was purified to apparent homogeneity by anion-exchange and gel permeation chromatography. The recombinant XEG has a molecular mass of 23,600, an isoelectric point of 3.4, and is optimally stable at a pH of 3.4 and temperature below 30 degreesC. The enzyme hydrolyzes structurally diverse xyloglucans from various sources, but hydrolyzes no other cell wall component and can therefore be considered a xyloglucan-specific endo -beta-1, 4-glucanohydrolase. XEG hydrolyzes its substrates with retention of the anomeric configuration. The Kmof the recombinant enzyme is 3.6 mg/ml, and its specific activity is 260 micromol/min per mg protein. The enzyme was tested for its ability to solubilize xyloglucan oligosaccharides from plant cell walls. It was shown that treatment of plant cell walls with XEG yields only xyloglucan oligosaccharides, indicating that this enzyme can be a powerful tool in the structural elucidation of xyloglucans.
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Affiliation(s)
- M Pauly
- Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology, University of Georgia, 220 Riverbend Road, Athens,GA 30602-4712, USA
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Sulová Z, Takácová M, Steele NM, Fry SC, Farkas V. Xyloglucan endotransglycosylase: evidence for the existence of a relatively stable glycosyl-enzyme intermediate. Biochem J 1998; 330 ( Pt 3):1475-80. [PMID: 9494122 PMCID: PMC1219298 DOI: 10.1042/bj3301475] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Xyloglucan endotransglycosylases (XETs) catalyse the breakdown of xyloglucan molecules predominantly by transglycosylation. In this process, fragments of cleaved polysaccharide are preferentially transferred to other xyloglucan molecules or their oligosaccharide subunits, with overall retention of the anomeric configuration of the glycosidic bond. In accordance with the theory, we propose that the cleavage and re-formation of the glycosidic bond in xyloglucan involves the formation of a glycosyl-enzyme intermediate which decomposes by transfer of the glycosyl moiety to a suitable carbohydrate acceptor. XETs from nasturtium seed cotyledons, mung bean hypocotyls and cauliflower florets interacted with xyloglucan to form complexes of high Mr as judged by gel-permeation chromatography. The nasturtium enzyme also showed evidence of XET-xyloglucan complex-formation according to anion-exchange chromatography and adsorption of the complex to filter paper on the basis of affinity of its xyloglucan moiety for cellulose. The XET-xyloglucan complex was stable in water, 6 M urea and acidic and alkaline buffers (pH 2.5-9.5), but readily decomposed by transferring its glycosyl moiety to xyloglucan-derived oligosaccharides or by incubation with the strong nucleophile imidazole at pH 3.8-9.6. These results strongly support the assumption that XET forms a relatively stable covalently linked glycosyl-enzyme intermediate.
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Affiliation(s)
- Z Sulová
- Institute of Chemistry, Slovak Academy of Sciences, 84238 Bratislava, Slovakia
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Sakurai N. Dynamic function and regulation of apoplast in the plant body. JOURNAL OF PLANT RESEARCH 1998; 111:133-148. [PMID: 0 DOI: 10.1007/bf02507160] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
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30
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Cellulose as a biological sink of CO2. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s0167-2991(98)80751-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
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