2010Feb_Nature_Genome sequencing and analysis of the model grass Brachypodium distachyon.pdf

ARTICLES Genome sequencing and analysis of the model grass Brachypodium distachyon The International Brachypodium Initiative* Three subfamilies of grasses, the Ehrhartoideae, Panicoideae and Pooideae, provide the bulk of human nutrition and are poised to become major sources of renewable energy. Here we describe the genome sequence of the wild grass Brachypodium distachyon (Brachypodium), which is, to our knowledge, the first member of the Pooideae subfamily to be sequenced. Comparison of the Brachypodium, rice and sorghum genomes shows a precise history of genome evolution across a broad diversity of the grasses, and establishes a template for analysis of the large genomes of economically important pooid grasses such as wheat. The high-quality genome sequence, coupled with ease of cultivation and transformation, small size and rapid life cycle, will help Brachypodium reach its potential as an important model system for developing new energy and food crops. Grasses provide the bulk of human nutrition, and highly productive grasses are promising sources of sustainable energy1. The grass family (Poaceae) comprises over 600 genera and more than 10,000 species that dominate many ecological and agricultural systems2,3. So far, genomic efforts have largely focused on two economically important grass subfamilies, the Ehrhartoideae (rice) and the Panicoideae (maize, sorghum, sugarcane and millets). The rice4 and sorghum5 genome sequences and a detailed physical map of maize6 showed extensive conservation of gene order5,7 and both ancient and rela- tively recent polyploidization. Most cool season cereal, forage and turf grasses belong to the Pooideae subfamily, which is also the largest grass subfamily. The genomes of many pooids are characterized by daunting size and complexity. For example, the bread wheat genome is approximately 17,000 megabases (Mb) and contains three independent genomes8. This has prohibited genome-scale comparisons spanning the three most economically