BcXTH1, a Brassica campestris homologue of Arabidopsis XTH9, is associated with cell expansion.
TL;DR: Investigation of the isolation and characterization of a XTH gene from a pistil cDNA library of Brassica campestris revealed that it is homologous to the XTH9 gene of Arabidopsis, and Immunoelectron microscopy shows that BcXTH1 is localized almost exclusively to the cell wall, supporting the conclusion that it participates in the regulation of cell expansion in B.campestris.
Abstract: Xyloglucan endotransglucosylase/hydrolases (XTHs) are a group of the enzymes that are responsible for reorganization of the cellulose–xyloglucan framework by catalyzing cleavage and religation of the xyloglucan chains in the plant cell wall. In this study, we report the isolation and characterization of a XTH gene from a pistil cDNA library of Brassica campestris. Sequence analysis of the gene, designated BcXTH1, revealed that it is homologous to the XTH9 gene of Arabidopsis. The highly conserved domain (DEIDFEFLG) found among all XTHs was also present in BcXTH1 but with the two amino acid substitutions (NEFDFEFLG) also found in Arabidopsis XTH9. These results suggest that BcXTH1 is the B. campestris homologue of XTH9. Expression analysis of BcXTH1 revealed that it was expressed in most of the plant organs. In situ hybridization showed that the gene is highly expressed in the floral primodia, especially in the epidermal cell layer. Southern blot analysis indicated that the BcXTH1 gene exists as a multi-copy gene in the B. campestris genome. The function of the BcXTH1 gene was deduced from using an overexpression strategy in Arabidopsis. Interestingly, the transgenic plants showed a pronounced cell expansion phenotype. Immunoelectron microscopy shows that BcXTH1 is localized almost exclusively to the cell wall, supporting our conclusion that it participates in the regulation of cell expansion in B. campestris.
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TL;DR: It is proposed that these specific XTH isoenzymes play a role in strengthening the side-walls of root-hairs and cell walls in the root differentiation zone after the completion of cell expansion.
Abstract: Xyloglucan endotransglucosylase/hydrolases (XTHs) are enzymes involved in the modification of load-bearing cell wall components. They cleave xyloglucan chains and, often, re-form bonds to the non-reducing ends of available xyloglucan molecules in plant primary cell walls. The enzymic properties and effects on root growth of two Arabidopsis thaliana XTHs belonging to subgroup I/II, that are predominantly expressed in root hairs and in non-elongating zones of the root, were analysed here. AtXTH14 and AtXTH26 were recombinantly produced in Pichia and subsequently purified. Both proteins were found to exhibit xyloglucan endotransglucosylase (XET; EC 2.4.1.207) but not xyloglucan endohydrolase (XEH; EC 3.2.1.151) activity. Their endotransglucosylase activity was at least 70x greater on xyloglucan rather than on mixed-linkage beta-glucan. Differences were found in pH- and temperature-dependence as well as in acceptor-substrate preferences. Furthermore, the specific activity of XET was approximately equal for the two enzymes. Removal of N-linked sugar residues by Endo H treatment reduced XET activity to 60%. Constant-load extensiometry experiments revealed that the enzymes reduce the extension in a model system of heat-inactivated isolated cell walls. When given to growing roots, either of these XTH proteins reduced cell elongation in a concentration-dependent manner and caused abnormal root hair morphology. This is the first time that recombinant and purified XTHs added to growing roots have exhibited a clear effect on cell elongation. It is proposed that these specific XTH isoenzymes play a role in strengthening the side-walls of root-hairs and cell walls in the root differentiation zone after the completion of cell expansion.
144 citations
Cites background from "BcXTH1, a Brassica campestris homol..."
...In addition, high expression of a Brassica campestris homologue of AtXTH9 in Arabidopsis evoked a pronounced increase in cell expansion (Shin et al., 2006), and loss of function of AtXTH21 restricted the growth of primary roots and caused an obvious dwarf phenotype in Arabidopsis (Liu et al.,…...
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...In addition, high expression of a Brassica campestris homologue of AtXTH9 in Arabidopsis evoked a pronounced increase in cell expansion (Shin et al., 2006), and loss of function of AtXTH21 restricted the growth of primary roots and caused an obvious dwarf phenotype in Arabidopsis (Liu et al....
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TL;DR: Evidence is provided that the SIZ1 gene controls cell division and elongation through regulation of the SA level and that XTH8 and XTH31 genes may be responsible for reduced leaf cell expansion.
Abstract: The post-translational conjugation of small ubiquitin-related modifiers (SUMOs) to other proteins is involved in regulation of many processes in eukaryotic development; although its role in plant development is beginning to be dissected. Previously, we demonstrated that the siz1 mutant, which is impaired in SUMO E3 ligase, showed a dwarf-like shoot phenotype with accumulation of salicylic acid (SA), and the expression of nahG, a bacterial salicylate hydroxylase that catabolizes SA, in siz1 reduced the SA level and suppressed dwarfism. Herein, we provide evidence that the SIZ1 gene controls cell division and elongation through regulation of the SA level. Mature siz1-2 and siz1-3 plants exhibited a dwarf-like shoot phenotype that is attributable to decreased leaf cell volume and number relative to the wild type. Cell division and expansion defects caused by siz1 were also suppressed by the expression of nahG. Expression of XTH8 and XTH31, encoding xyloglucan endotransglycosylase/ hydrolase, which are thought to facilitate leaf cell expansion, was down-regulated in siz1 leaves. However, reduced XTH8 and XTH31 expression in siz1 plants was restored in nahG siz1-2 plants. These results indicate that SIZ1 regulates cell growth and plant development with regulation of SA accumulation. Also, XTH8 and XTH31 genes may be responsible for reduced leaf cell expansion.
134 citations
Cites background from "BcXTH1, a Brassica campestris homol..."
...Expression of the Brassica campestris XTH1 in Arabidopsis enhanced in stem elongation, which is caused by enhanced 15 directional cell expansion (Shin et al., 2006). acl (acaulis) and tfl (terminal flower) mutations cause a reduction in cell size (Tsukaya et al., 1993; 1995) and in height (Alvarez…...
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TL;DR: This review documents and discusses studies demonstrating the importance of timely cell wall modification during plant stress responses by focusing on a well-researched subset of wall modifying proteins.
Abstract: Cell wall modification is an important aspect of plant acclimation to environmental stresses. Structural changes of the existing cell wall mediated by various cell wall modifying proteins help a plant adjust to environmental changes by regulating growth and policing the entry of biotic agents. For example, accelerated shoot growth during submergence and shading allows some plants to escape these unfavorable conditions. This is mediated by the regulation of wall modifying proteins that alter cell wall structure and allow it to yield to turgor, thus fueling cellular expansion. Regulation of cell wall protein activity results in growth modulation during drought, where maintenance of root growth through changes in wall extensibility is an important adaptation to water deficit. Freeze-tolerant plants adjust their cell wall properties to prevent freezing-induced dehydration and also use the cell wall as a barrier against ice crystal propagation. Cell wall architecture is an important determinant of plant resist...
130 citations
Additional excerpts
...This is supported by several studies where XTH gene expression and enzyme activity positively correlated with elongation growth (Vissenberg et al., 2000; Shin et al., 2006)....
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TL;DR: The function of GhXTH1 in mediating cotton fiber elongation was analyzed in transgenic cotton plants that express a transgene consisting of the Gh XTH1 coding sequence under transcriptional control of the CaMV 35S promoter.
Abstract: Plant cell wall extensibility is mediated, in part, by xyloglucan endotransglycosylases/hydrolases (XTH) that are able to cleave and reattach xyloglucan polymers that make up the hemicelluloses matrix of type I cell walls. In Arabidopsis and other plants, XTHs are encoded by relatively large gene families that are regulated in specific spatial and temporal patterns. In silico screening of a cotton expressed sequence tag (EST) database identified 23 sequences with close sequence similarity to Arabidopsis XTH coding sequences. Analysis of full-length cotton cDNAs derived from these ESTs allow for the identification of three distinct GhXTH cDNAs (denoted GhXTH1, GhXTH2 and GhXTH3) based primarily on their 3′ untranslated sequences. The three GhXTH genes were expressed differently with GhXTH1 predominantly expressed in elongating cotton fibers. The function of GhXTH1 in mediating cotton fiber elongation was analyzed in transgenic cotton plants that express a transgene consisting of the GhXTH1 coding sequence under transcriptional control of the CaMV 35S promoter. Plants that over-expressed GhXTH1 had increased XTH activity and produced mature cotton fibers that were between 15 and 20% longer than wild-type cotton plants under both greenhouse and field growth conditions. Segregation analysis showed that the 35S::GhXTH1 transgene acts as a dominant fiber length allele in transgenic cotton. These results confirm that GhXTH1 is the predominant XTH in elongating fibers and its expression limits cotton fiber elongation.
110 citations
Cites background from "BcXTH1, a Brassica campestris homol..."
...Shin et al. (2006) reported that ectopic expression of BcXTH1 from Brassica campestris (a close ortholog of AtXTH9) in Arabidopsis strongly affected cell elongation resulting in substantial increase in vegetative growth....
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...Shin et al. (2006) reported that ectopic expression of BcXTH1 from Brassica campestris (a close ortholog of AtXTH9) in Arabidopsis strongly affected cell elongation resulting in substantial increase in vegetative growth....
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TL;DR: The molecular, physiological and anatomical adjustments underlying salt tolerance in glycophytic and halophytic model tree species, such as Populus euphratica in terrestrial habitats, and mangrove species along coastlines are reviewed.
Abstract: Saline and sodic soils that cannot be used for agriculture occur worldwide. Cultivating stress-tolerant trees to obtain biomass from salinized areas has been suggested. Various tree species of economic importance for fruit, fibre and timber production exhibit high salinity tolerance. Little is known about the mechanisms enabling tree crops to cope with high salinity for extended periods. Here, the molecular, physiological and anatomical adjustments underlying salt tolerance in glycophytic and halophytic model tree species, such as Populus euphratica in terrestrial habitats, and mangrove species along coastlines are reviewed. Key mechanisms that have been identified as mediating salt tolerance are discussed at scales from the genetic to the morphological level, including leaf succulence and structural adjustments of wood anatomy. The genetic and transcriptomic bases for physiological salt acclimation are salt sensing and signalling networks that activate target genes; the target genes keep reactive oxygen species under control, maintain the ion balance and restore water status. Evolutionary adaptation includes gene duplication in these pathways. Strategies for and limitations to tree improvement, particularly transgenic approaches for increasing salt tolerance by transforming trees with single and multiple candidate genes, are discussed.
106 citations
Cites background from "BcXTH1, a Brassica campestris homol..."
...Arabidopsis plants overexpressing XTHs show anatomical alterations (Cho et al. 2006; Shin et al. 2006)....
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...Similarly, the overexpression of pepper CaXTH3 or of Brassica campestris BcXTH in Arabidopsis altered leaf morphology (Cho et al. 2006; Shin et al. 2006), but this effect was apparently not observed in CaXTH3-expressing tomato (Choi et al....
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...Similarly, the overexpression of pepper CaXTH3 or of Brassica campestris BcXTH in Arabidopsis altered leaf morphology (Cho et al. 2006; Shin et al. 2006), but this effect was apparently not observed in CaXTH3-expressing tomato (Choi et al. 2011)....
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References
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TL;DR: A new approach to rapid sequence comparison, basic local alignment search tool (BLAST), directly approximates alignments that optimize a measure of local similarity, the maximal segment pair (MSP) score.
88,255 citations
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...Sequence comparisons were conducted using Clustal W (Altschul et al. 1990)....
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TL;DR: A new method for the identification of signal peptides and their cleavage sites based on neural networks trained on separate sets of prokaryotic and eukaryotic sequence that performs significantly better than previous prediction schemes and can easily be applied on genome-wide data sets.
Abstract: We have developed a new method for the identification of signal peptides and their cleavage sites based on neural networks trained on separate sets of prokaryotic and eukaryotic sequence. The method performs significantly better than previous prediction schemes and can easily be applied on genome-wide data sets. Discrimination between cleaved signal peptides and uncleaved N-terminal signal-anchor sequences is also possible, though with lower precision. Predictions can be made on a publicly available WWW server.
5,480 citations
"BcXTH1, a Brassica campestris homol..." refers methods in this paper
...The signal peptide cleavage site was predicted by the SignalP program (Nielsen et al. 1997)....
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01 Jan 1997
TL;DR: In this paper, a new method for the identification of in performance compared with the weight matrix method signal peptides and their cleavage sites based on neural (Arrigo et al., 1991; Ladunga et al, 1991; Schneider and networks trained on separate sets of prokaryotic and eukaryotic sequence.
Abstract: applicable prediction methods with significant improvements We have developed a new method for the identification of in performance compared with the weight matrix method signal peptides and their cleavage sites based on neural (Arrigo et al., 1991; Ladunga et al., 1991; Schneider and networks trained on separate sets of prokaryotic and Wrede, 1993). eukaryotic sequence. The method performs significantly better than previous prediction schemes and can easily be Materials and methods applied on genome-wide data sets. Discrimination between cleaved signal peptides and uncleaved N-terminal signal- The data were taken from SWISS-PROT version 29 (Bairoch anchor sequences is also possible, though with lower preci- and Boeckmann, 1994). The data sets were divided into sion. Predictions can be made on a publicly available prokaryotic and eukaryotic entries and the prokaryotic data sets WWW server.
5,191 citations
TL;DR: This review integrates information on the chemical structure of individual polymers with data obtained from new techniques used to probe the arrangement of the polymers within the walls of individual cells consistent with the physical properties of the wall and its components.
Abstract: Advances in determination of polymer structure and in preservation of structure for electron microscopy provide the best view to date of how polysaccharides and structural proteins are organized into plant cell walls. The walls that form and partition dividing cells are modified chemically and structurally from the walls expanding to provide a cell with its functional form. In grasses, the chemical structure of the wall differs from that of all other flowering plant species that have been examined. Nevertheless, both types of wall must conform to the same physical laws. Cell expansion occurs via strictly regulated reorientation of each of the wall's components that first permits the wall to stretch in specific directions and then lock into final shape. This review integrates information on the chemical structure of individual polymers with data obtained from new techniques used to probe the arrangement of the polymers within the walls of individual cells. We provide structural models of two distinct types of walls in flowering plants consistent with the physical properties of the wall and its components.
3,417 citations
"BcXTH1, a Brassica campestris homol..." refers background in this paper
...In higher plants, the cell wall is composed of a complex network of cellulose microfibrils in which non-cellulosic matrix polymers compact together with structural proteins, conferring strength and extensibility to the cell wall (Carpita and Gibeaut 1993)....
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TL;DR: It is proposed that XET is responsible for cutting and rejoining intermicrofibrillar xyloglucan chains and that it thus causes the wall-loosening required for plant cell expansion.
Abstract: 1. Cell-free extracts of all plants tested contained a novel enzyme activity (xyloglucan endotransglycosylase, XET) able to transfer a high-Mr portion from a donor xyloglucan to a suitable acceptor such as a xyloglucan-derived nonasaccharide (Glc4Xyl3GalFuc; XG9). 2. A simple assay for the enzyme, using [3H]XG9 and based on the ability of the [3H]polysaccharide product to bind to filter paper, is described. 3. The enzyme was highly specific for xyloglucan as the glycosyl donor, and showed negligible transglycosylation of other polysaccharides, including CM-cellulose. 4. The Km for XG9 was 50 microM; certain other 3H-labelled xyloglucan oligosaccharides also acted as acceptors, and certain non-radioactive xyloglucan oligosaccharides competed with [3H]XG9 as acceptor; the minimum acceptor structure was deduced to be: [formula: see text] 5. The pH optimum was approx. 5.5 and the enzyme was less than half as active at pH 7.0. The enzyme was slightly activated by Ca2+, Mg2+, Mn2+, spermidine, ascorbate and 2-mercaptoethanol, and inhibited by Ag+, Hg2+, Zn2+ and La3+. 6. XET activity was essentially completely extracted by aqueous solutions of low ionic strength; Triton X-100, Ca2+, La3+, and Li+ did not enhance extraction. Negligible activity was left in the unextractable (cell-wall-rich) residue. 7. The enzyme differed from the major cellulases (EC 3.2.1.4) of pea in: (a) susceptibility to inhibition by cello-oligosaccharides, (b) polysaccharide substrate specificity, (c) inducibility by auxin, (d) requirement for salt in the extraction buffer and (e) activation by 2-mercaptoethanol. XET is therefore concluded to be a new enzyme activity (xyloglucan: xyloglucan xyloglucanotransferase; EC 2.4.1.-). 8. XET was detected in extracts of the growing portions of dicotyledons, monocotyledons (graminaceous and liliaceous) and bryophytes. 9. The activity was positively correlated with growth rate in different zones of the pea stem. 10. We propose that XET is responsible for cutting and rejoining intermicrofibrillar xyloglucan chains and that it thus causes the wall-loosening required for plant cell expansion.
815 citations
"BcXTH1, a Brassica campestris homol..." refers background in this paper
...rearrangement of the cell wall matrix, there is growing evidence that they may also be involved in cell expansion (Fry et al. 1992; Xu et al. 1996; Campbell and Braam 1999)....
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...In higher plants, the XTHs, first identified and characterized by Fry et al. (1992) and Nishitani and Tominaga (1992), cleave and religate xyloglucan polymers and thereby participate in loosening and rearrangement of the cell wall of growing tissues (Fry 1989; Rose et al. 2002)....
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...In addition to the roles of XTH in loosening and rearrangement of the cell wall matrix, there is growing evidence that they may also be involved in cell expansion (Fry et al. 1992; Xu et al. 1996; Campbell and Braam 1999)....
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