Development of Cellulosic Secondary Walls in Flax Fibers Requires β-Galactosidase
| Autor: | Anastasiya V. Snegireva, Melissa Roach, Tatyana Gorshkova, Natalia Y. Mokshina, Neil Hobson, Ajay Badhan, Michael K. Deyholos |
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| Rok vydání: | 2011 |
| Předmět: |
Linum
Physiology Molecular Sequence Data Biochemical Processes and Macromolecular Structures Plant Science Polysaccharide Models Biological Rhamnose Gene Expression Regulation Enzymologic Cell wall chemistry.chemical_compound X-Ray Diffraction Cell Wall Gene Expression Regulation Plant Flax Spectroscopy Fourier Transform Infrared Botany Genetics RNA Messenger Fiber Cellulose Phylogeny chemistry.chemical_classification Plant Stems biology Galactose Plants Genetically Modified beta-Galactosidase biology.organism_classification Hypocotyl chemistry Bast fibre Biophysics RNA Interference Phloem Secondary cell wall |
| Zdroj: | Plant Physiology. 156:1351-1363 |
| ISSN: | 1532-2548 |
| DOI: | 10.1104/pp.111.172676 |
| Popis: | Bast (phloem) fibers, tension wood fibers, and other cells with gelatinous-type secondary walls are rich in crystalline cellulose. In developing bast fibers of flax (Linum usitatissimum), a galactan-enriched matrix (Gn-layer) is gradually modified into a mature cellulosic gelatinous-layer (G-layer), which ultimately comprises most of the secondary cell wall. Previous studies have correlated this maturation process with expression of a putative β-galactosidase. Here, we demonstrate that β-galactosidase activity is in fact necessary for the dynamic remodeling of polysaccharides that occurs during normal secondary wall development in flax fibers. We found that developing stems of transgenic (LuBGAL-RNAi) flax with reduced β-galactosidase activity had lower concentrations of free Gal and had significant reductions in the thickness of mature cellulosic G-layers compared with controls. Conversely, Gn-layers, labeled intensively by the galactan-specific LM5 antibody, were greatly expanded in LuBGAL-RNAi transgenic plants. Gross morphology and stem anatomy, including the thickness of bast fiber walls, were otherwise unaffected by silencing of β-galactosidase transcripts. These results demonstrate a specific requirement for β-galactosidase in hydrolysis of galactans during formation of cellulosic G-layers. Transgenic lines with reduced β-galactosidase activity also had biochemical and spectroscopic properties consistent with a reduction in cellulose crystallinity. We further demonstrated that the tensile strength of normal flax stems is dependent on β-galactosidase-mediated development of the phloem fiber G-layer. Thus, the mechanical strength that typifies flax stems is dependent on a thick, cellulosic G-layer, which itself depends on β-galactosidase activity within the precursor Gn-layer. These observations demonstrate a novel role for matrix polysaccharides in cellulose deposition; the relevance of these observations to the development of cell walls in other species is also discussed. |
| Databáze: | OpenAIRE |
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