Submitted to: Frontiers in Plant Science
Publication Type: Review Article
Publication Acceptance Date: 12/23/2016
Publication Date: 1/18/2017
Citation: Hatfield, R.D., Rancour, D.M., Marita, J.M. 2017. Grass cell walls: A story of cross-linking. Frontiers in Plant Science. 7:2056-2082. Interpretive Summary:
Technical Abstract: Cell wall matrices are complex composites mainly of polysaccharides, phenolics (monomers and polymers), and protein. We are beginning to understand the synthesis of these major wall components individually, but still have a poor understanding of how the cell wall components are assembled into complex matrices. Valuable insight has been gained by examining intact components to understand the individual elements that make up plant cell walls. Grasses are a unique group within the plant kingdom, not only for their important roles in global agriculture, but also for the unique complexity of their cell walls. Part of this uniqueness is the prominent role of ferulate incorporation into cell wall matrices (C3 and C4 types) that leads to a cross-linked matrix. Incorporation of p-coumarates as part of the lignin structure also adds to the unique complexity of grass cell walls. Feruoylation results in a wall with individual hemicellulosic polysaccharides (arabinoxylans) covalently linked to each other and to lignin. Evidence strongly suggests that ferulates not only cross-link arabinoxylans, but may be important factors in lignification of the cell wall. Therefore, the distribution of ferulates on arabinoxylans could provide a means of directing lignification within specific regions of the matrix and have a significant impact upon local cell wall organization. The role of other phenolics in cell wall formation such as p-coumarates (which can have concentrations higher than ferulates) remains unknown. It is possible that p-coumarates assist in the formation of lignin, especially syringyl rich lignins. The uniqueness of the grass cell wall may not be so much in the composition of the wall, but how the individual components are organized into a highly functioning wall matrix. These features are discussed, and working models are provided to illustrate how changing the organization of feruoylation and p-coumaroylation could lead to differing cell wall properties.