Molecular Plant Advance Access originally published online on July 12, 2009
Molecular Plant 2009 2(5):933-942; doi:10.1093/mp/ssp047
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Identification of Lignin and Polysaccharide Modifications in Populus Wood by Chemometric Analysis of 2D NMR Spectra from Dissolved Cell Walls
a Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden
b Department of Biochemistry, and Great Lakes Bioenergy Research Center, University of Wisconsin, Madison, WI 53706, USA
c Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
d US Dairy Forage Research Center, USDA-Agricultural Research Service, Madison, WI 53706, USA
1 To whom correspondence should be addressed. E-mail: mattias.hedenstrom{at}chem.umu.se, fax (+46)907867655, tel. (+46)907865788
2D 13C–1H HSQC NMR spectroscopy of acetylated cell walls in solution gives a detailed fingerprint that can be used to assess the chemical composition of the complete wall without extensive degradation. We demonstrate how multivariate analysis of such spectra can be used to visualize cell wall changes between sample types as high-resolution 2D NMR loading spectra. Changes in composition and structure for both lignin and polysaccharides can subsequently be interpreted on a molecular level. The multivariate approach alleviates problems associated with peak picking of overlapping peaks, and it allows the deduction of the relative importance of each peak for sample discrimination. As a first proof of concept, we compare Populus tension wood to normal wood. All well established differences in cellulose, hemicellulose, and lignin compositions between these wood types were readily detected, confirming the reliability of the multivariate approach. In a second example, wood from transgenic Populus modified in their degree of pectin methylesterification was compared to that of wild-type trees. We show that differences in both lignin and polysaccharide composition that are difficult to detect with traditional spectral analysis and that could not be a priori predicted were revealed by the multivariate approach. 2D NMR of dissolved cell wall samples combined with multivariate analysis constitutes a novel approach in cell wall analysis and provides a new tool that will benefit cell wall research.
Key Words: Aspen • biostatistics • cell walls • multivariate data analysis • NMR spectroscopy • tension wood