Poaceae genomes: going from unattainable to becoming a model clade for comparative plant genomics.

Genomics has an immense potential for improving our understanding of critical issues in plant growth and development, some of which can be applied to improvement of crop production. Midway into the second decade of genomics, genome and transcriptome sequencing efforts with the Poaceae are impressive given the technical and fiscal challenges presented by the typically large, repetitive genomes foundwithin the Poaceae (Smith and Flavell, 1975; Arumuganathan and Earle, 1991; SanMiguel et al., 1996). Indeed, as of October 30, 2008, there are 10,847,522 Poaceae sequences representing 11,142 Mb (11.1 Gb) in GenBank, confirming the fast pace of sequence generation for the Poaceae. With respect to representation of genera and species within the Poaceae, 2,740 of the approximately 10,000 species reported within the Poaceae (http:// www.kew.org/scihort/poaceae.html) have at least one sequence in GenBank. Genome-scale datasets represent a more narrow phylogenetic base and of the 47 Poaceae species with genome or transcriptome sequences (Table I; discussed below), 32 are derived from the BEP clade (Bambusoideae, Ehrhartoideae, Pooideae) and 15 are derived from the PACCMAD clade (Panicoideae, Arundinoideae, Chloridoideae, Centothecoideae, Micrairoideae, Aristidoideae, and Danthonioideae) and represent five subfamilies, nine tribes, and 24 genera within the Poaceae (Fig. 1). This article is intended to provide a short introduction to genome sequencing efforts in the Poaceae and an abbreviated report of completed and ongoing genome and transcriptome sequencing efforts for Poaceae species to not only demonstrate the potential of species within the Poaceae for understanding plant biological processes but also to highlight the Poaceae as a model family for comparative genomics.