Brachypodium is closely related to the cool season grasses, and is an emerging model system for the diverse and economically important grain, forage and turf crops that these groups encompass. Diploid accessions of Brachypodium (2n=2x=10) have c values of 0.36-0.39 pg or about twice Arabidopsis. Analysis of genome sequences from a perennial sister species - B. sylvaticum - shows remarkable similarity to the genome composition of rice, including a high gene density of 1 gene per 8-10 kb and a relatively simple pattern of known repeated elements. Gene order is generally conserved with wheat and rice, but the sequences of Brachypodium genes are much more similar to temperate grasses than to rice. Thus the small Brachypodium genome can be used as an accurate template for the much larger polyploid genomes of closely- related energy crops such as switchgrass and Miscanthus (elephant grass) and food crops such as wheat. Moreover Brachypodium is inbreeding, small in stature, can be grown rapidly, and is readily transformed by Agrobacterium tumefaciens. This combination of desirable attributes underlies the burgeoning research interest in the species.
David Garvin at the University of Minnesota (http://agronomy.coafes.umn.edu/Garvin_ David_F___USDA-ARS___Ph_D.html) has developed and disseminated highly inbred diploid Brachypodium distachyon lines to serve as reference genotypes for community research. One of these lines, Bd21, was adopted by the International Brachypodium Initiative (IBI) (http://www.brachypodium.org/ as the community standard line for genomics and functional genomics.
Evolutionary relationships between Brachypodium and temperate grass crops (data from John Vogel, USDA Albany).
The IBI has recently made a successful bid to the US Dept of Energy for sequencing the Bd21 genome and transcriptome. This work will start later in 2006 and should be completed by the end of 2007 (http://www.jgi.doe.gov/News/news_7_11_06.html ). The genome sequence will provide a tremendously useful resource for assembling and analysing large genomic segments of wheat, barley and forage grasses. This work, together with functional genomics resources, promises to dramatically accelerate progress in cereal genomics and crop improvement.
