Author
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Ralph, John |
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Submitted to: Meeting Abstract
Publication Type: Proceedings Publication Acceptance Date: 3/21/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Down-regulating the lignin biosynthetic pathway was initially aimed at lowering lignin levels in attempts to improve a variety of natural and industrial processes (e.g. from ruminant digestibility of forages to chemical pulping of woody plants). There are now several approaches which have successfully lowered lignin levels while maintaining vigorously growing plants. However, it is the results from other targeted enzymes, particularly those late in the pathway, that have lead to the suggestion that lignification is a far more malleable process than previously considered. There appears to be the opportunity to alter the structure (and therefore the consequent properties) of lignins well beyond previously held compositional bounds. It further appears that the very building blocks of lignin, the monolignols themselves, can be to some degree replaced by other pathway-compatible phenols. Such revelations open up unprecedented opportunities to (re-)engineer this vital plant polymer for improved utilization of valuable plant resources. The emerging picture is still based on empirical observations of mutant and transgenic plants. The extent to which lignins may be successfully modified and the ability of the plant to remain viable and competitive are issues remaining to be fully explored. Already, however, plants are available that have extraordinarily non-conventional lignins. For example, in COMT-deficient plants, the novel 5-hydroxyconiferyl alcohol monomer incorporates intimately into the lignin structure as would a "normal" monomer, but produces novel benzodioxane structures. Detailed structural studies are revealing that the hydroxycinnamyl aldehydes also incorporate intimately into lignins of CAD-deficient angiosperms. |
