Cell wall composition throughout development for the model grass Brachypodium distachyon

Authors: Rancour, David; Marita, Jane; Hatfield, Ronald

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2012
Publication Date: 11/14/2012
Citation: Rancour, D.M., Marita, J.M., Hatfield, R.D. 2012. Cell wall composition throughout development for the model grass Brachypodium distachyon. Frontiers in Plant Science. DOI: 10.3389/fpls.2012.00266.

Interpretive Summary: Grasses are globally important as sources of fiber, as feed for ruminant animals, and as a proposed feedstock for cellulosic biofuels. Grasses are classified as monocots because their seedlings have one cotyledon or leaf-like structure, unlike dicot seedlings that have two cotyledons. Brachypodium distanchyon, a monocot grass, has been proposed to fill a need for a grass model plant to parallel the use of the dicot model plant, Arabidopsis thaliana. Model plant species are intended to facilitate research programs by closely mimicking their related crop plants with the benefit of reducing time needed for generation-to-generation growth, minimizing space needed to grow the plants, and providing the capacity to easily track the genetics and traits of the system for improvement. It is expected that results from studying the model plant could then help guide targeted research in crop plants with savings in time and cost. To facilitate validation of Brachypodium distanchyon as a forage grass model, we have performed chemical analysis of cell walls isolated from distinct plant parts throughout plant development in order to generate a developmental cell wall composition map for Brachypodium. The results of this work provide an information base for the grass research community from which future research in the genetic manipulation of cell wall composition (in part to identify factors that would result in improved cell wall energy conversion efficiency) can be compared.

Technical Abstract: Temperate perennial grasses are important worldwide as livestock nutritive energy sources and potential feedstock for lignocellulosic biofuel production. The annual temperate grass, Brachypodium distanchyon, has been championed as a useful model system to facilitate biological research in agriculturally important temperate forage grasses based on phylogenetic relationships. To physically corroborate genetic predictions, we determined the chemical composition profiles of tissue-specific cell walls throughout the development of two common diploid accessions of Brachypodium distanchyon, Bd21-3 and Bd21. Chemical analysis was performed on cell walls isolated from four distinct developmental stages: 1) embryonic callus, 2) 12-day seedling, 3) vegetative-to-reproductive transition, and 4) mature seed-fill stages and evaluation of plant part (leaves, sheaths, stems, and roots). Wall composition variation for lignin, hydroxycinnamates, uronosyls, neutral sugars, and protein suggests that Brachypodium distanchyon is similar chemically to agriculturally important forage grasses, and little compositional difference exists between accessions Bd21-3 and Bd21. Therefore, Brachypodium distanchyon should be a useful model system for genetic manipulation of cell wall composition to determine the impact upon functional characteristics such as rumen digestibility or energy conversion efficiency for bioenergy production.