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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Cell Wall Biology and Utilization Research » Research » Publications at this Location » Publication #317638
Title: Incorporation of p-coumarates into the cell walls of alfalfa changes the lignin composition

Author
item Marita, Jane
item Hatfield, Ronald
item Rancour, David

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/5/2015
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: In general, monocots can contain a significant amount of an ester-linked p-coumarate (pCA) in their cell walls, but its function is unclear. One hypothesis is that pCA aids in the formation of syringyl-rich regions during lignification. Alfalfa (Medicago sativa), a dicot, is a cultivated perennial forage crop and an important food component in dairy production systems around the world. Unlike many monocots, this dicot does not contain significant amounts of ester-linked pCA in its stem cell walls, but there appear to be measurable amounts present in its leaf cell walls. The pCA incorporated into leaves does not appear to be linked to lignin. Expression of a maize p-coumaroyl:CoA hydroxycinnamyl alcohol transferase (pCAT) in alfalfa was used to test the influence that ester-linked pCA has on lignin composition in alfalfa stem and leaf cell walls and to determine what affect any such changes have on its digestibility. In general, isolated lignin of alfalfa cell walls is guaiacyl-rich, especially in the leaves. If pCA-conjugates help in the formation of syringyl-based lignin, cell walls of pCAT-expressing alfalfa should exhibit both increased ester-linked pCA and sinapyl alcohol content of the lignin. This study revealed that fresh plant tissue and isolated alfalfa leaf and stem cell walls from pCAT-expressing lines had increased amounts of ester-linked pCA after alkaline hydrolysis when compared to controls. Total cell wall lignin amounts were similar even when pCAT expression was high. Gel-state 2D-NMR analysis of cell walls revealed changes in lignin syringyl and guaiacyl content in stems. Therefore, pCAT expression in the dicot, alfalfa, altered the lignin composition and increased the amount of ester-linked pCA on cell walls, especially in stems. This supports the hypothesis that ester-linked pCA on cell walls influences lignin formation and composition, but does not result in increased lignification.