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Secondary Cell Wall (secondary + cell_wall)
Selected AbstractsMolecular and Biochemical Evidence for Phenylpropanoid Synthesis and Presence of Wall-linked Phenolics in Cotton FibersJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 7 2009Ling Fan Abstract The mature cotton (Gossypium hirsutum L.) fiber is a single cell with a typically thickened secondary cell wall. The aim of this research was to use molecular, spectroscopic and chemical techniques to investigate the possible occurrence of previously overlooked accumulation of phenolics during secondary cell wall formation in cotton fibers. Relative quantitative reverse transcription-polymerase chain reaction analysis showed that GhCAD6 and GhCAD1 were predominantly expressed among seven gene homologs, only GhCAD6 was up-regulated during secondary wall formation in cotton fibers. Phylogenic analysis revealed that GhCAD6 belonged to Class I and was proposed to have a major role in monolignol biosynthesis, and GhCAD1 belonged to Class III and was proposed to have a compensatory mechanism for monolignol biosynthesis. Amino acid sequence comparison showed that the cofactor binding sites of GhCADs were highly conserved with high similarity and identity to bona fide cinnamyl alcohol dehydrogenases. The substrate binding site of GhCAD1 is different from GhCAD6. This difference was confirmed by the different catalytic activities observed with the enzymes. Cell wall auto-fluorescence, Fourier transform infrared spectroscopy (FTIR), high-performance liquid chromatography (HPLC) and chemical analyses confirmed that phenolic compounds were bound to the cell walls of mature cotton fibers. Our findings may suggest a potential for genetic manipulation of cotton fiber properties, which are of central importance to agricultural, cotton processing and textile industries. [source] Stress generation in the tension wood of poplar is based on the lateral swelling power of the G-layerTHE PLANT JOURNAL, Issue 4 2008Luna Goswami Summary The mechanism of active stress generation in tension wood is still not fully understood. To characterize the functional interdependency between the G-layer and the secondary cell wall, nanostructural characterization and mechanical tests were performed on native tension wood tissues of poplar (Populus nigra × Populus deltoids) and on tissues in which the G-layer was removed by an enzymatic treatment. In addition to the well-known axial orientation of the cellulose fibrils in the G-layer, it was shown that the microfibril angle of the S2-layer was very large (about 36°). The removal of the G-layer resulted in an axial extension and a tangential contraction of the tissues. The tensile stress,strain curves of native tension wood slices showed a jagged appearance after yield that could not be seen in the enzyme-treated samples. The behaviour of the native tissue was modelled by assuming that cells deform elastically up to a critical strain at which the G-layer slips, causing a drop in stress. The results suggest that tensile stresses in poplar are generated in the living plant by a lateral swelling of the G-layer which forces the surrounding secondary cell wall to contract in the axial direction. [source] Secondary Cell Wall Deposition in Developing Secondary Xylem of PoplarJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 2 2010Minako Kaneda Although poplar is widely used for genomic and biotechnological manipulations of wood, the cellular basis of wood development in poplar has not been accurately documented at an ultrastructural level. Developing secondary xylem cells from hybrid poplar (Populus deltoides x P. trichocarpa), which were actively making secondary cell walls, were preserved with high pressure freezing/freeze substitution for light and electron microscopy. The distribution of xylans and mannans in the different cell types of developing secondary xylem were detected with immunofluorescence and immuno-gold labeling. While xylans, detected with the monoclonal antibody LM10, had a general distribution across the secondary xylem, mannans were enriched in the S2 secondary cell wall layer of fibers. To observe the cellular structures associated with secondary wall production, cryofixed fibers were examined with transmission electron microscopy during differentiation. There were abundant cortical microtubules and endomembrane activity in cells during the intense phase of secondary cell wall synthesis. Microtubule-associated small membrane compartments were commonly observed, as well as Golgi and secretory vesicles fusing with the plasma membrane. [source] Walls are thin 1 (WAT1), an Arabidopsis homolog of Medicago truncatula NODULIN21, is a tonoplast-localized protein required for secondary wall formation in fibersTHE PLANT JOURNAL, Issue 3 2010Philippe Ranocha Summary By combining Zinnia elegans in vitro tracheary element genomics with reverse genetics in Arabidopsis, we have identified a new upstream component of secondary wall formation in xylary and interfascicular fibers. Walls are thin 1 (WAT1), an Arabidopsis thaliana homolog of Medicago truncatula NODULIN 21 (MtN21), encodes a plant-specific, predicted integral membrane protein, and is a member of the plant drug/metabolite exporter (P-DME) family (transporter classification number: TC 2.A.7.3). Although WAT1 is ubiquitously expressed throughout the plant, its expression is preferentially associated with vascular tissues, including developing xylem vessels and fibers. WAT1:GFP fusion protein analysis demonstrated that WAT1 is localized to the tonoplast. Analysis of wat1 mutants revealed two cell wall-related phenotypes in stems: a defect in cell elongation, resulting in a dwarfed habit and little to no secondary cell walls in fibers. Secondary walls of vessel elements were unaffected by the mutation. The secondary wall phenotype was supported by comparative transcriptomic and metabolomic analyses of wat1 and wild-type stems, as many transcripts and metabolites involved in secondary wall formation were reduced in abundance. Unexpectedly, these experiments also revealed a modification in tryptophan (Trp) and auxin metabolism that might contribute to the wat1 phenotype. Together, our data demonstrate an essential role for the WAT1 tonoplast protein in the control of secondary cell wall formation in fibers. [source] | ||||||||||