Investigating Brachypodium distachyon as a Model System for Plant Biofuels Research

Abstract

Plant biomass has been proposed for the production of biofuels. Grasses are an attractive source of biomass due to their fast growth rate and abundance. The mechanical and chemical breakdown of grass cell walls releases simple sugars that are stored in the cellulose and hemicellulose of the plant. These can then be fermented to produce a variety of fuels. Brachypodium distachyon (Brachypodium) possesses many desirable qualities of a model system such as small genome, diploid accessions, small stature, and short life cycle. Brachypodium is a powerful tool for investigating how to make grasses better biofuel crops. Although Brachypodium is already being used for such research, a great deal of information still needs to be gathered on this grass to fully exploit it as a model for biofuel research. Two distinct features of Brachypodium were investigated here. First, the ability of different Brachypodium genotypes to regenerate back to healthy fertile plants through the tissue culture method was studied. A second study examined the effect of cold treatment (vernalization) on plant height, biomass, days to spike emergence, and the amount of fermentable sugars released from mature stems. The comparison of regeneration efficiencies of five Brachypodium genotypes showed that each genotype was able to form compact embryogenic calli (CECs) and regenerate green shoots from callus tissue at different efficiencies. CEC formation efficiencies ranged from 22% to 86%. Efficiencies for regeneration of healthy fertile plants will be gathered in the future as plants mature. The ability of these Brachypodium genotypes to form CECs is significant because CECs are necessary for transforming plants to study how grasses can be altered for more efficient biofuel production. Vernalization of three Brachypodium genotypes for different time periods (0, 7, 14, 21, and 28days) showed that with increased vernalization time, height and days to spike emergence were reduced. The most dramatic reduction in days to spike emergence occurred between zero and two weeks. Data on fermentable sugar release of different Brachypodium genotypes will be provided in the future by a collaborating laboratory.