Formation of syringyl-rich lignins in maize as influenced by feruloylated xylans and <Emphasis Type="Italic">p</Emphasis>-coumaroylated monolignols |
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Authors: | John H Grabber Fachuang Lu |
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Institution: | (1) U.S. Dairy Forage Research Center, Agricultural Research Service, U.S. Department of Agriculture, 1925 Linden Drive West, Madison, WI 53706, USA;(2) Department of Agricultural and Biological Systems Engineering, University of Wisconsin, Madison, WI 53706, USA |
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Abstract: | Abstract
Grass cell walls are atypical because their xylans are acylated with ferulate and lignins are acylated with p-coumarate. To probe the role and interactions of these p-hydroxycinnamates during lignification, feruloylated primary cell walls isolated from maize cell suspensions were lignified
with coniferyl and sinapyl alcohols and with varying levels of p-coumarate esters. Ferulate xylan esters enhanced the formation of wall-bound syringyl lignin more than methyl p-coumarate, however, maximal concentrations of syringyl lignin were only one-third that of guaiacyl lignin. Including sinapyl
p-coumarate, the presumed precursor of p-coumaroylated lignins, with monolignols unexpectedly accelerated peroxidase inactivation, interfered with ferulate copolymerization
into lignin, and had minimal or adverse effects on cell wall lignification. Free phenolic groups of p-coumarate esters in isolated maize lignin and pith cell walls did not undergo oxidative coupling with each other or with
added monolignols. Thus, the extensive formation of syringyl-rich lignins and the functional role of extensive lignin acylation
by p-coumarate in grasses remains a mystery. |
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Keywords: | Cell wall p-Coumarate Cross-linking Ferulate Lignin Peroxidase |
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