Quantitative P-31 NMR spectroscopy of lignins from transgenic poplars

Milled wood lignins isolated from genetically modified poplar trees were st udied by quantitative P-31 NMR spectroscopy, in combination with thioacidol ysis 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 li gnin structure. In contrast, severe CAD deficiency alters the lignin struct ure more profoundly by decreasing the syrinayl/guaiacyl ratio and increasin g the degree of condensation of the lignin. The most severe alterations wer e observed in the lignins from the COMT-transformed lines.