Abstract
BackgroundBrachypodium distachyon constitutes an excellent model species for grasses. It is a small, easily propagated, temperate grass with a rapid life cycle and a small genome. It is a self-fertile plant that can be transformed with high efficiency using Agrobacteria and callus derived from immature embryos. In addition, considerable genetic and genomic resources are becoming available for this species in the form of mapping populations, large expressed sequence tag collections, T-DNA insertion lines and, in the near future, the complete genome sequence. The development of Brachypodium as a model species is of particular value in the areas of cell wall and biomass research, where differences between dicots and grasses are greatest. Here we explore the effect of mild conditions of pretreatment and hydrolysis in Brachypodium stem segments as a contribution for the establishment of sensitive screening of the saccharification properties in different genetic materials.ResultsThe non-cellulosic monosaccharide composition of Brachypodium is closely related to grasses of agricultural importance and significantly different from the dicot model Arabidopsis thaliana. Diluted acid pretreatment of stem segments produced significant release of sugars and negatively affected the amount of sugars obtained by enzymatic hydrolysis. Monosaccharide and oligosaccharide analysis showed that the hemicellulose fraction is the main target of the enzymatic activity under the modest hydrolytic conditions used in our assays. Scanning electron microscopy analysis of the treated materials showed progressive exposure of fibrils in the stem segments.ConclusionResults presented here indicate that under mild conditions cellulose and hemicellulose are hydrolysed to differing extents, with hemicellulose hydrolysis predominating. We anticipate that the sub-optimal conditions for hydrolysis identified here will provide a sensitive assay to detect variations in saccharification among Brachypodium plants, providing a useful analytical tool for identifying plants with alterations in this trait.
Highlights
Brachypodium distachyon constitutes an excellent model species for grasses
Monosaccharide composition of Brachypodium stems Brachypodium is closely related to agronomically important grasses, making it a potential model species from a phylogenetic point of view [6]
To examine whether Brachypodium relatedness to important crop grasses is maintained at the level of cell wall composition, we compared the monosaccharide composition of stem cell wall from several grass species with that of Arabidopsis, a wellcharacterised dicot model
Summary
Brachypodium distachyon constitutes an excellent model species for grasses It is a small, propagated, temperate grass with a rapid life cycle and a small genome. The high costs associated with the three biological steps involved in the conversion of lignocellulose to biofuels (enzyme production, biomass hydrolysis and fermentation of the released sugars) have driven numerous efforts to make the overall biochemical conversion more efficient [7]. These efforts have been directed to reduce the costs of enzymes, and to optimise the configuration of all the steps of the process [8]. Using Brachypodium as a model for understanding the characteristics of the grass cell wall involved in the process of saccharification will require a detailed characterisation of the saccharification in this material under different conditions [6]
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