| 1. |
- Aspeborg, Henrik, et al.
(författare)
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Carbohydrate-active enzymes involved in the secondary cell wall biogenesis in hybrid aspen
- 2005
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 137:3, s. 983-997
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Tidskriftsartikel (refereegranskat)abstract
- Wood formation is a fundamental biological process with significant economic interest. While lignin biosynthesis is currently relatively well understood, the pathways leading to the synthesis of the key structural carbohydrates in wood fibers remain obscure. We have used a functional genomics approach to identify enzymes involved in carbohydrate biosynthesis and remodeling during xylem development in the hybrid aspen Populus tremula x tremuloides. Microarrays containing cDNA clones from different tissue-specific libraries were hybridized with probes obtained from narrow tissue sections prepared by cryosectioning of the developing xylem. Bioinformatic analyses using the sensitive tools developed for carbohydrate-active enzymes allowed the identification of 25 xylem-specific glycosyltransferases belonging to the Carbohydrate-Active EnZYme families GT2, GT8, GT14, GT31, GT43, GT47, and GT61 and nine glycosidases (or transglycosidases) belonging to the Carbohydrate-Active EnZYme families GH9, GH10, GH16, GH17, GH19, GH28, GH35, and GH51. While no genes encoding either polysaccharide lyases or carbohydrate esterases were found among the secondary wall-specific genes, one putative O-acetyltransferase was identified. These wood-specific enzyme genes constitute a valuable resource for future development of engineered fibers with improved performance in different applications.
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| 2. |
- Andersson-Gunneras, S., et al.
(författare)
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Biosynthesis of cellulose-enriched tension wood in Populus : global analysis of transcripts and metabolites identifies biochemical and developmental regulators in secondary wall biosynthesis
- 2006
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Ingår i: The Plant Journal. - Malden : Wiley-Blackwell. - 0960-7412 .- 1365-313X. ; 45:2, s. 144-165
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Tidskriftsartikel (refereegranskat)abstract
- Stems and branches of angiosperm trees form tension wood (TW) when exposed to a gravitational stimulus. One of the main characteristics of TW, which distinguishes it from normal wood, is the formation of fibers with a thick inner gelatinous cell wall layer mainly composed of crystalline cellulose. Hence TW is enriched in cellulose, and deficient in lignin and hemicelluloses. An expressed sequence tag library made from TW-forming tissues in Populus tremula (L.) x tremuloides (Michx.) and data from transcript profiling using microarray and metabolite analysis were obtained during TW formation in Populus tremula (L.) in two growing seasons. The data were examined with the aim of identifying the genes responsible for the change in carbon
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| 3. |
- Bourquin, V., et al.
(författare)
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Xyloglucan endotransglycosylases have a function during the formation of secondary cell walls of vascular tissues
- 2002
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Ingår i: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 14:12, s. 3073-3088
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Tidskriftsartikel (refereegranskat)abstract
- Xyloglucan transglycosylases (XETs) have been implicated in many aspects of cell wall biosynthesis, but their function in vascular tissues, in general, and in the formation of secondary walls, in particular, is less well understood. Using an in situ XET activity assay in poplar stems, we have demonstrated XET activity in xylem and phloem fibers at the stage of secondary wall formation. Immunolocalization of fucosylated xylogucan with CCRC-M1 antibodies showed that levels of this species increased at the border between the primary and secondary wall layers at the time of secondary wall deposition. Furthermore, one of the most abundant XET isoforms in secondary vascular tissues (PttXET16A) was cloned and immunolocalized to fibers at the stage of secondary wall formation. Together, these data strongly suggest that XET has a previously unreported role in restructuring primary walls at the time when secondary wall layers are deposited, probably creating and reinforcing the connections between the primary and secondary wall layers. We also observed that xylogucan is incorporated at a high level in the inner layer of nacreous walls of mature sieve tube elements.
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| 4. |
- Kumar, Manoj, et al.
(författare)
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An update on the nomenclature for the cellulose synthase genes in Populus
- 2009
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Ingår i: Trends in Plant Science. - : Elsevier BV. - 1360-1385 .- 1878-4372. ; 14:5, s. 248-254
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Forskningsöversikt (refereegranskat)abstract
- Cellulose synthase (CesA) is a central catalyst in the generation of the plant cell wall biomass and is, therefore, the focus of intense research. Characterization of individual CesA genes from Populus species has led to the publication of several different naming conventions for CesA gene family members in this model tree. To help reduce the resulting confusion, we propose here a new phylogeny-based CesA nomenclature that aligns the Populus CesA gene family with the established Arabidopsis thaliana CesA family structure.
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| 5. |
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| 6. |
- Schrader, J., et al.
(författare)
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A high-resolution transcript profile across the wood-forming meristem of poplar identifies potential regulators of cambial stem cell identity
- 2004
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Ingår i: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 16:9, s. 2278-2292
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Tidskriftsartikel (refereegranskat)abstract
- Plant growth is the result of cell proliferation in meristems, which requires a careful balance between the formation of new tissue and the maintenance of a set of undifferentiated stem cells. Recent studies have provided important information on several genetic networks responsible for stem cell maintenance and regulation of cell differentiation in the apical meristems of shoots and roots. Nothing, however, is known about the regulatory networks in secondary meristems like the vascular cambium of trees. We have made use of the large size and highly regular layered organization of the cambial meristem to create a high-resolution transcriptional map covering 220 mum of the cambial region of aspen (Populus tremula). Clusters of differentially expressed genes revealed substantial differences in the transcriptomes of the six anatomically homogenous cell layers in the meristem zone. Based on transcriptional and anatomical data, we present a model for the position of the stem cells and the proliferating mother cells in the cambial zone. We also provide sets of marker genes for different stages of xylem and phloem differentiation and identify potential regulators of cambial meristem activity. Interestingly, analysis of known regulators of apical meristem development indicates substantial similarity in regulatory networks between primary and secondary meristems.
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| 7. |
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| 8. |
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| 9. |
- Siedlecka, A, et al.
(författare)
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The small subunit ADP-glucose pyrophosphorylase (ApS) promoter mediates okadaic acid-sensitive uidA expression in starch-synthesizing tissues and cells in Arabidopsis
- 2003
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Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 217:2, s. 184-192
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Tidskriftsartikel (refereegranskat)abstract
- Transgenic plants of Arabidopsis thaliana Heynh., transformed with a bacterial beta-glucuronidase (GUS) gene under the control of the promoter of the small subunit (ApS) of ADP-glucose pyrophosphorylase (AGPase), exhibited GUS staining in leaves (including stomata), stems, roots and flowers. Cross-sections of stems revealed GUS staining in protoxylem parenchyma, primary phloem and cortex. In young roots, the staining was found in the root tips, including the root cap, and in vascular tissue, while the older root-hypocotyl axis showed prominent staining in the secondary phloem and paratracheary parenchyma of secondary xylem. The GUS staining co-localized with ApS protein, as found by tissue printing using antibodies against ApS. Starch was found only in cell and tissue types exhibiting GUS staining and ApS labelling, but not in all of them. For example, starch was lacking in the xylem parenchyma and secondary phloem of the root-hypocotyl axis. Sucrose potently activated ApS gene expression in leaves of wild-type (wt) plants, and in transgenic seedlings grown on sucrose medium where GUS activity was quantified with 4-methylumbelliferyl-beta-glucuronide as substrate. Okadaic acid, an inhibitor of protein phosphatases 1 and 2A, completely blocked expression of ApS in mature leaves of wt plants and prevented GUS staining in root tips and flowers of the transgenic plants, suggesting a similar signal transduction mechanism for ApS expression in various tissues. The data support the key role of AGPase in starch synthesis, but they also underlie the ubiquitous importance of the ApS gene for AGPase function in all organs/tissues of Arabidopsis.
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| 10. |
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