Quantitative P-31 NMR spectroscopy of lignins from transgenic poplars

Milled wood lignins isolated from genetically modified poplar trees were studied by quantitative P-31 NMR spectroscopy, in combination with thioacidolysis and mild alkaline hydrolysis. The genetic transformation of the trees included down regulation of CAD and COMT enzyme activities. These analyses confirmed that moderate CAD down-regulation does not substantially alter lignin structure. In contrast, severe CAD deficiency alters the lignin structure more profoundly by decreasing the syrinayl/guaiacyl ratio and increasing the degree of condensation of the lignin. The most severe alterations were observed in the lignins from the COMT-transformed lines.