Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/18/2005
Publication Date: 8/4/2005
Citation: Ralph, J., Lu, F., Akiyama, T., Kim, H., Marita, J.M., Reddy, M.S., Dixon, R.A. 2005. Tools for lignin structural analysis; applications to C3H-downregulation. In: Proceedings of Biosynthesis of Plant Cell Walls, August 4-7, 2005, Pacific Grove, California. p. 11. Interpretive Summary:
Technical Abstract: The effects on lignification of downregulating most of the genes for enzymes on the monolignol biosynthetic pathway have been reasonably well studied. The exception to this is the crucial hydroxylase, cinnamate 3-hydroxylase (C3H), taking p-coumarate to caffeate. The Noble Foundation group has been exploring the transformation of commercially important alfalfa for improved digestibility and other traits. C3H-deficient plants have been successfully generated. Preliminary degradative analyses (by thioacidolysis and the DFRC method) confirm the depression of guaiacyl and syringyl contents and a sharp elevation in the p-hydroxyphenyl levels. As such, the lignification in these plants has been perturbed to a far higher degree than the previously studied perturbation known to enhance p-hydroxyphenyl levels, that occurring in softwood compression wood (where the level reaches about 10%). NMR analysis (coupled with studies on synthetically-coupled p-coumaryl-alcohol-rich polymers) show that the lignins are strikingly different from those studied in any other natural, mutant, or transgenic plant to date.