NMR characterization of altered lignins extracted from tobacco plants down-regulated for lignification enzymes cinnamylalcohol dehydrogenase and cinnamoyl-CoA reductase
Homologous antisense constructs were used to down-regulate tobacco cinnamyl-alcohol dehydrogenase (CAD; EC 1.1.1.195 ) and cinnamoyl-CoA reductase (CCR; EC 1.2.1.44 ) activities in the lignin monomer biosynthetic pathway. CCR converts activated cinnamic acids (hydroxycinnamoyl–SCoAs) to cinnamaldehy...
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Published in | Proceedings of the National Academy of Sciences - PNAS Vol. 95; no. 22; pp. 12803 - 12808 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
National Acad Sciences
27.10.1998
The National Academy of Sciences |
Subjects | |
Online Access | Get full text |
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Summary: | Homologous antisense constructs were used to down-regulate tobacco cinnamyl-alcohol dehydrogenase (CAD; EC 1.1.1.195 ) and cinnamoyl-CoA reductase (CCR; EC 1.2.1.44 ) activities in the lignin monomer biosynthetic pathway. CCR converts activated cinnamic acids (hydroxycinnamoyl–SCoAs) to cinnamaldehydes; cinnamaldehydes are then reduced to cinnamyl alcohols by CAD. The transformations caused the incorporation of nontraditional components into the extractable tobacco lignins, as evidenced by NMR. Isolated lignin of antisense-CAD tobacco contained fewer coniferyl and sinapyl alcohol-derived units that were compensated for by elevated levels of benzaldehydes and cinnamaldehydes. Products from radical coupling of cinnamaldehydes, particularly sinapaldehyde, which were barely discernible in normal tobacco, were major components of the antisense-CAD tobacco lignin. Lignin content was reduced in antisense-CCR tobacco, which displayed a markedly reduced vigor. That lignin contained fewer coniferyl alcohol-derived units and significant levels of tyramine ferulate. Tyramine ferulate is a sink for the anticipated build-up of feruloyl–SCoA, and may be up-regulated in response to a deficit of coniferyl alcohol. Although it is not yet clear whether the modified lignins are true structural components of the cell wall, the findings provide further indications of the metabolic plasticity of plant lignification. An ability to produce lignin from alternative monomers would open new avenues for manipulation of lignin by genetic biotechnologies. monolignol/genetic modification/antisense RNA/coniferyl alcohol/feruloyl-CoA |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2 To whom reprint requests should be addressed at: U.S. Dairy Forage Research Center, USDA-ARS, 1925 Linden Drive West, Madison, WI 53706-1108. e-mail: jralph@facstaff.wisc.edu. Communicated by Ron Sederoff, North Carolina State University, Raleigh, NC |
ISSN: | 0027-8424 1091-6490 |
DOI: | 10.1073/pnas.95.22.12803 |