ARS | Publication request: 5-HYDROXYCONIFERYL ALCOHOL AS A MONOLIGNOL IN COMT-DEFICIENT ANGIOSPERMS

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: June 11, 2001
Publication Date: N/A

Technical Abstract: COMT is the enzyme responsible for methylating 5-hydroxyconiferyl aldehyde, on the way to producing syringyl units. It is deficient in recently examined transgenic poplars downregulated by two different methods, in F5H-upregulated transgenic arabidopsis, and in a brown-midrib maize mutant (bm3). In all cases, 5-hydroxyconiferyl alcohol incorporated intimately into the lignin. Benzodioxane (4-O-beta/5-O-alpha) structures are produced and can be characterized by their beautiful NMR correlations, by their survival through DFRC-degradation, and their partial survival through thioacidolysis. The level of detail revealed by these methods provides evidence 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. Demonstrated endwise polymerization into lignins suggests that 5-hydroxyconiferyl alcohol shoul be recognized as an authentic lignin monomer in these angiosperms.