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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #115760
Title: INCORPORATION OF 5-HYDROXYCONIFERYL ALCOHOL INTO LIGNINS OF COMT-DEFICIENT POPLAR

Author
item Ralph, John
item MARITA, JANE - UNIV WISCONSIN, MADISON
item LU, FACHUANG - UNIV WISCONSIN, MADISON
item LAPIERRE, CATHERINE - INRA-GRIGNON, FRANCE
item BOERJAN, WOUT - U GENT, BELGIUM
item PILATE, GILLES - INRA-ORLEANS, FRANCE
item JOUANIN, LISE - INRA-VERSAILLES, FRANCE

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/20/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The perturbation of "normal" lignification that occurs when lignin-biosynthetic-pathway genes/enzymes are down-regulated provides enhanced opportunities to understand the lignification process. Down-regulation of some enzymes in the pathway introduces new phenylpropanoid "monomers" into lignification and produces new structures in the lignin polymer. The utilization of the plant cell wall, e.g. for chemical pulping, is affected by such compositional and structural changes which are therefore important to characterize. Such studies also provide a basis for even more wide-ranging manipulation of lignin structure, beyond currently held compositional bounds. COMT, the enzyme responsible for methylating 5-hydroxyconiferyl aldehyde, on the way to producing syringyl units was downregulated in poplar by various methods, and is deficient in the brown midrib3 mutant of maize. In all cases, 5-hydroxyconiferyl alcohol lincorporates intimately into the lignin. Benzodioxane structures are produced and can be characterized by their beautiful NMR correlations, by their survival through DFRC-degradation (Derivatization Followed by Reductive Cleavage), and their partial survival through thioacidolysis (where they were first found). The level of detail revealed by these methods provides reliable proof that the novel 5-hydroxyconiferyl alcohol monomer cross-couples with syringyl and guaiacyl units into the growing lignin oligomer, and that normal monolignols then add to the new 5-hydroxyguaiacyl terminus producing benzodioxanes. The endwise polymerization is therefore elegantly revealed, and is evidence that 5-hydroxyconiferyl alcohol must be recognized as an authentic lignin monomer.