Formation of syringyl-rich lignins in maize as influenced by feruloylated xylans and p-coumaroylated monolignols.
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.
Grabber
John H
JH
US Dairy Forage Research Center, Agricultural Research Service, US Department of Agriculture, 1925 Linden Drive West, Madison, WI 53706, USA. jgrabber@wisc.edu
Lu
Fachuang
F
D002473:Cell Wall / Q000187:drug effects / Q000201:enzymology; D003373:Coumaric Acids / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008031:Lignin / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism; D014990:Xylans / Q000378:metabolism*; D003313:Zea mays / Q000187:drug effects / Q000378:metabolism*
D003373:Coumaric Acids; D014990:Xylans; C516502:diferulic acid; C434469:syringyl monolignol; D008031:Lignin; C004999:ferulic acid; D006861:Hydrogen Peroxide; D010544:Peroxidases