ARS | Publication request: DETERMINING THE ROLE OF P-COUMARYL TRANSFERASE IN LIGNIFICATION OF GRASSES

Submitted to: Molecular Breeding of Forage and Turf Conference
Publication Type: Abstract Only
Publication Acceptance Date: February 28, 2003
Publication Date: N/A

Technical Abstract: Several plant species undergo acylation of their lignin during growth and development. Grasses form unique acylated lignins involving p-coumarate residues primarily ester linked to sinapyl alcohol residues. In addition, warm season grasses differ markedly from cool season grasses regarding the degree of acylation. Warm season grasses, such as maize, tend to have twice as much p-coumarate attached to lignin as cool season species with levels up to 15% of the total lignin. The amount of p-coumaroylation of lignins varies within maize species but generally parallels the levels of total Klason lignin. One potential role of p-coumaroyl residues is to aid in the formation of syringyl type lignins that generally occur in the latter stages of lignification. Peroxidases in maize do not oxidize sinapyl alcohol as readily as coniferyl alcohol. It is thought that p-coumaroyl residues are rapidly oxidized and transfer the radical to sinapyl alcohol allowing it to readily undergo radical coupling reactions. Towards elucidating this role, we have focused efforts on characterizing the p-coumaroyl transferase in maize. We have developed a convenient biological system for the production of activated p-coumaroyl residues (p-coumaroyl-CoA). 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 HPLC-PDA, allows for rapid assessment of transferase activity in tissue extracts and correct product formation is authenticated by GC-MS. Results indicate that the p-coumaroyl transferase found in lignifiying tissues of maize mirrors lignification.