Reduced lignin in transgenic plants containing a caffeic acidO-methyltransferase antisense gene

Abstract

Lignin is a major structural polymer of secondarily thickened plant vascular tissue and fibres, imparting mechanical strength to stems and trunks and hydrophobicity to conducting vessels. Constitutive expression of a lucerne caffeic acid 3-O-methyltransferase antisense RNA in transgenic tobacco leads to a significant reduction in lignin content, particularly in the younger parts of the stems, without apparent alterations in lignin monomer composition. These observations open up the possibility of genetically manipulating plants with reduced lignin for improved processing and biomass digestibility.

Downregulation of Caffeic Acid 3-O-Methyltransferase and Caffeoyl CoA 3-O-Methyltransferase in Transgenic Alfalfa: Impacts on Lignin Structure and Implications for the Biosynthesis of G and S Lignin

“…Interestingly, complete loss of CCOMT protein in the CCOMT antisense line ACC305 was accompanied by an increase in COMT protein level, as documented in Figure 5C, and in COMT enzymatic activity (see below). The above results indicate that expression of OMT sequences from the bean PAL2 promoter results in downregulation of COMT and CCOMT that is similar to or greater than that obtained in previous studies in tobacco and poplar (Ni et al, 1994;Atanassova et al, 1995;Van Doorsselaere et al, 1995;Zhong et al, 1998), in contrast with our previous results using 35S promoter-driven constructs in alfalfa.…”

“…Most studies on genetic modification of lignin biosynthesis in transgenic plants have utilized the cauliflower mosaic virus 35S promoter to drive expression of sense or antisense lignification-associated genes (Halpin et al, 1994;Ni et al, 1994;Atanassova et al, 1995;Doorsselaere et al, 1995;Piquemal et al, 1998;Zhong et al, 1998;Baucher et al, 1999). However, antisense downregulation of COMT and CCOMT in transgenic alfalfa is inefficient and relatively weak using 35S promoter constructs (V.J.H.…”

“…There have been several reports on the effects of downregulation of COMT activity on lignin content and composition in transgenic plants (Ni et al, 1994;Atanassova et al, 1995;Van Doorsselaere et al, 1995;Zhong et al, 1998). The results of these studies have been somewhat contradictory, possibly due to unspecified differences in tissue maturity, use of homologous versus heterologous transgenes, and use of different methods for lignin analysis.…”

Lignin and Lignan Biosynthesis: Distinctions and Reconciliations

“…Instead, the molecular approach has primarily been devoted to attempts at determining the effects of differentially expressing genes encoding putative regulatory enzymes in the lignin biosynthetic pathway (Figure 3) (56)(57)(58)(59)(60)(61)(62). As can be seen, there are essentially only four types of transformations beyond cinnamic acid, namely aromatic hydroxylations (63)(64)(65), O-methylations (66-68), CoA ligations and (consecutive) NADPH dependent reductions (69).…”

Structural Characterization of Modified Lignin in Transgenic Tobacco Plants in Which the Activity of 4-Coumarate:Coenzyme A Ligase Is Depressed

“…In the past decade many genes for enzymes related to the biosynthesis of lignin have been cloned from a variety of plant species, and the expression of these genes at various stages of lignification has been characterized (Sederoff et al, 1994;Whetten and Sederoff, 1995). In several recent studies transgenic plants carrying chimeric genes for the enzymes involved in lignin biosynthesis were generated and the altered lignins in these transformants were analyzed (Elkind et al, 1990;Dwivedi et al, 1994;Halpin et al, 1994;Ni et al, 1994;Atanassova et al, 1995;Doorsselaere et al, 1995;Hibino et al, 1995;Mcintyre et al, 1996). The analysis of lignins in these transgenic plants has provided useful information about the role of each enzyme in lignin * Corresponding author; e-mail kajita-s@ccm.mpm.co.jp; fax 81-298-64-4310.…”