Plant Cell Wall

NMR fingerprinting of the components of finely divided plant cell walls swelled in DMSO has been recently described. Cell wall gels, produced directly in the NMR tube with perdeutero-dimethylsulfoxide, allowed the acquisition of well resolved/dispersed 2D (13)C-(1)H correlated solution-state NMR spectra of the entire array of wall polymers, without the need for component fractionation. That is, without actual solubilization, and without apparent structural modification beyond that inflicted by the ball milling and ultrasonication steps, satisfactorily interpretable spectra can be acquired that reveal compositional and structural details regarding the polysaccharide and lignin components in the wall. Here, the profiling method has been improved by using a mixture of perdeuterated DMSO and pyridine (4 : 1, v/v). Adding pyridine provided not only easier sample handling because of the better mobility compared to the DMSO-d(6)-only system but also considerably elevated intensities and improved resolution of the NMR spectra due to the enhanced swelling of the cell walls. This modification therefore provides a more rapid method for comparative structural evaluation of plant cell walls than is currently available. We examined loblolly pine (Pinus taeda, a gymnosperm), aspen (Populus tremuloides, an angiosperm), kenaf (Hibiscus cannabinus, an herbaceous plant), and corn (Zea mays L., a grass, i.e., from the Poaceae family). In principle, lignin composition (notably, the syringyl : guaiacyl : p-hydroxyphenyl ratio) can be quantified without the need for lignin isolation. Correlations for p-coumarate units in the corn sample are readily seen, and a variety of the ferulate correlations are also well resolved; ferulates are important components responsible for cell wall cross-linking in grasses. Polysaccharide anomeric correlations were tentatively assigned for each plant sample based on standard samples and various literature data. With the new potential for chemometric analysis using the 2D NMR fingerprint, this gel-state method may provide the basis for an attractive approach to providing a secondary screen for selecting biomass lines and for optimizing biomass processing and conversion efficiencies.

Pyrolysis-GC-MS pyrograms from a series of alfalfa preparations, a grass, an angiosperm wood, a cellulose, and an arabinoxylan were obtained under pyrolytic conditions optimal for aromatic components of plant cell walls. Approximately 130 pyrolytic fragments have been ...

Plant cell walls have been shown to contain acetyl groups in hemicelluloses and pectin. The gene aes1 , encoding the acetyl esterase (Aes1) of Hypocrea jecorina , was identified by amino-terminal sequencing, peptide mass spectrometry, and genomic sequence analyses. The coded polypeptide had 348 amino acid residues with the first 19 serving as a secretion signal peptide. The calculated molecular mass and isoelectric point of the secreted enzyme were 37,088 Da and pH 5.89, respectively. No significant homology was found between the predicated Aes1 and carbohydrate esterases of known families, but putative aes1 orthologs were found in genomes of many fungi and bacteria that produce cell wall-degrading enzymes. The aes1 transcript levels were high when the fungal cells were induced with sophorose, cellulose, oat spelt xylan, lactose, and arabinose. The recombinant Aes1 produced by H. jecorina transformed with aes1 under the cellobiohydrolase I promoter displayed properties similar to th...

Bacterial wilt incidence was reduced by 38.1% and 100% in silicon-treated plants of the moderately resistant tomato genotype King Kong 2 and the resistant genotype Hawaii 7998 grown in peat substrate. At 5 days post inoculation the bacterial population was significantly reduced in stems and roots of genotype Hawaii 7998, and in stems of King Kong 2 in silicon-treated plants compared to non-treated plants, indicating a silicon-induced resistance, since silicon accumulated in roots, but not in stems, while a tolerance effect was observed in the susceptible genotype L390. Characterization of possible molecular mechanisms involved in silicon-mediated resistance by immuno-histochemical analysis of stem cell walls indicated silicon-induced changes in the pectic polysaccharide structure. After infection homogalacturonan with non-blockwise degradation of methyl-esters was increased in vessel walls in non-silicon-treated plants, but not in silicon-treated plants, possibly indicating the acti...