Strong decrease in lignin content without significant alteration of plant development is induced by simultaneous down-regulation of cinnamoyl CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) in tobacco plants
Different transgenic tobacco lines down-regulated for either one or two enzymes of the monolignol pathway were compared for their lignin content and composition, and developmental patterns. The comparison concerned CCR and CAD down-regulated lines (homozygous or heterozygous for the transgene) and the hybrids resulting from the crossing of transgenic lines individually altered for CCR or CAD activities. Surprisingly, the crosses containing only one allele of each antisense transgene, exhibit a dramatic reduction of lignin content similar to the CCR down-regulated parent but, in contrast to this transgenic line, display a normal phenotype and only slight alterations of the shape of the vessels. Qualitatively the lignin of the double transformant displays characteristics more like the wild type control than either of the other transgenics. In the transgenics with a low lignin content, the transformations induced other biochemical changes involving polysaccharides, phenolic components of the cell wall and also soluble phenolics. These results show that the ectopic expression of a specific transgene may have a different impact depending on the genetic background and suggest that the two transgenes present in the crosses may operate synergistically to reduce the lignin content. In addition, these data confirm that plants with a severe reduction in lignin content may undergo normal development at least in controlled conditions.
Document Type: Research Article
Affiliations: 1: UMR CNRS/UPS 5546, Signaux et Messages Cellulaires chez les Végétaux, Pole de Biotechnologie Végétale, 24 Chemin de Borde-Rouge BP17 Auzeville 31326 Castanet-Tolosan, France, 2: Department of Biological Sciences, University of Dundee, Dundee DD1 3: Laboratoire de Chimie Biologique Institut National Agronomique 78850 Thiverval-Grignon, France, 4: HN, Scotland, UK, 5: Commissariat à l'Energie Atomique, Département d'Ecophysiologie Végétale et Microbiologie, Cadarache, Bât. 177, 13108 Saint Paul lez Durance Cedex, France
Publication date: November 1, 2001