ARS | Publication request: CELL WALL CROSS-LINKING IN GRASSES BY FERULATES AND DEHYDRODIFERULATES

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: April 1, 1998
Publication Date: N/A

Technical Abstract: Ferulic acid in grasses is an important intermediary in cross-linking polysaccharides to lignin. Until recently, the mechanisms and extent of this cross-linking have been poorly understood and vastly underestimated. Active incorporation of ferulates directly into the lignin polymer via oxidative coupling (radical) mechanisms has been unequivocally demonstrated dand predominates over the traditionally invoked "passive" incorporation vi addition to lignin quinone methide intermediates. Such incorporation produces a range of structures from which ferulate cannot be released and therefore cannot be quantitated by traditional solvolytic methods. Additionally, ferulate polysaccharide esters dimerize, again via oxidative coupling, to produce a range of dehydrodiferulates, only one of which until recently had been recognized and quantitated. The total quantity of releasable dehydrodiferulates is up to 20-fold higher than determined in the past, and can account for over half of the total ferulate in the cell wall. Dehydrodiferulates also actively incorporate into lignins providing a unique method of simultaneously cross-linking polysaccharides to each other and to lignins. Dehydrodiferulates have now been found in a range of plant materials. Ferulates (and, presumably, dehydrodiferulates) also appear to function as initiation or nucleation sites for wall lignification. Ferulates have been found to attach exclusively to lignin monomers (and not lignin oligomers or polymers) and are thus critical entities in directing lignification and cell wall cross-linking during plant growth and development. The cross-linking of polysaccharides to each other and to lignin also has a marked impact on the degradability of wall polysaccharides.