Submitted to: Cell Wall Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 28, 2005
Publication Date: August 4, 2005
Citation: Hatfield, R.H., Marita, J.M., Frost, K. 2005 Lignin acylation in grasses [abstract]. Cell Wall Biosynthesis Meeting, Paper No.78 Technical Abstract: Acylation of lignin in plant cell walls during growth and development is a common occurrence among some plant species. Grasses form unique acylated lignins involving p-coumarate residues primarily linked to syringyl units in lignin. Warm season grasses (C4) differ markedly from cool season grasses (C3) regarding the degree of acylation. Warm season grasses (i.e., maize, grain sorghum) have about twice as many p-coumarates attached to lignin as cool season species with levels up to 15% of the total lignin. Levels of p-coumaroylation of lignins vary within maize species, but generally parallel the levels of total lignin. The exact role of p-coumaroylation in grass cell walls remains unclear. One potential role is to aid in the formation of syringyl type lignins that generally occur in the latter stages of lignification. Sinapyl alcohol is not oxidized as readily as coniferyl alcohol by maize cell wall peroxidases. Therefore, a possible mechanism utilizes p-coumarate residues that are rapidly oxidized, transferring their radical to sinapyl alcohol allowing it to undergo radical coupling reactions. Our efforts have focused on characterizing the p-coumaroyl transferase in maize to better understand the physiological and biochemical roles of lignin p-coumaroylation. A convenient biological system for the production of activated p-coumaroyl residues (p-coumaroyl-CoA) has been developed. The transferase of interest is a soluble enzyme that utilizes p-coumaryl-CoA as the activated donor molecule and sinapyl alcohol as the acceptor molecule. An assay system, based on GC-MS, allows for rapid assessment of transferase activity in tissue extracts and authentication of correct product formation. Results indicate that the p-coumaroyl transferase found in lignifying tissues of maize mirrors lignification.