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Taking advantage of the recent characterization of the cDNA encoding cinnamoyl-CoA reductase (CCR, EC 1.2. 1.44) in: Eucalyptus gunnii, antisense constructs have been introduced in tobacco plants in order to down-regulate this key enzyme of lignification. Primary transformants exhibiting reduction in CCR activity were obtained and a good correlation was observed between the decrease in the steady state level of CCR mRNA and the level of CCR activity. Lignin content and composition were examined in the progeny of primary transformants down-regulated for CCR activity and exhibiting one single T-DNA integration locus. All CCR down-regulated lines display common features, such as an orange brown coloration of the xylem cell walls, an increase in the syringyl over guaiacyl (S/G) ratio, and the presence of unusual cell wall bound phenolics. Moreover, the less severely depressed lines exhibited a normal …