Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 24, 2000
Publication Date: N/A
Technical Abstract: Ferulic acid is a unique molecule that is incorporated into many types of plant cell walls. Although found in a wide range of plants, ferulates are most predominate within species of the grass family. Ferulates are most commonly shuttled into cell walls ester-linked to terminal arabinosyl branches of arabinoxylans among the grasses. In dicots they are covalently linked to arabinosyl and galactosyl residues of pectic polysaccharides. It has long been recognized that the unique chemical nature of these molecules could lead to cross-links among polysaccharides within wall matrices; indeed, identification of the 5,5' dehydrodiferulate has established this role. We have recently shown that radical mediated cross coupling of ferulates is much more predominate than originally thought. Identification and accurate quantification of all the ferulate dehydrodimers has lead to the realization that ferulate mediated cross-linking may have been underestimated by a factor of 20. In some plants, as much as 70% of the total ferulate released from walls is in the form of dimers. Total ferulates (monomers and dimers) can account for a substantial part of the total wall matrix. Corn pericarp tissues can have up to 5% of their cell walls as ferulates. These findings suggest prominent structural roles for wall bound ferulates. Radical mediated coupling of ferulates provides a mechanism for altering structural characteristics of wall matrices that is under the complete control of the plant. Ferulates and diferulates will undergo radical coupling reactions with lignin monomers, resulting in an additional level of wall cross-linking. Incorporation into lignin may be as high as 50 to 60% with much of the ferulate bound in forms that are not releasable from the wall under normal hydrolytic conditions.