5 Grains of Knowledge: Genomics of Model Cereals

Abstract

The cultivated cereals, members of the Poaceae family of the angiosperms, provide about half of the calories consumed by humans and a growing share of biofuel. Together with their economic importance, the Poaceae are an attractive group for comparative genomics because they include many important crops with diverse native distributions and at least 35-fold variation in genome size (e.g., rice = 420 Mb; wheat = ~ 15,000 Mb). The independent domestication of rice in both Africa and Asia, sorghum in Africa, maize in America, and wheat in the Near East has provided an excellent study system in which to explore the genetic complexity of adapting plants to human use (for example, see Paterson et al. 1995; Paterson 2002).

Recent efforts to characterize Poaceae genomes better are reflected in their expansion from 1% to about 6% of the DNA sequence resources in GenBank (Paterson et al. 2003). This is exemplified by the nearly finished sequencing of each of two Oryza subspecies (see below), supplemented by exploratory genome-wide efforts in maize (Whitelaw et al. 2003) and sorghum (Bedell et al. 2005), and large EST and STS-based DNA marker collections for many others.

Collectively, genomic resources for diverse Poaceae promise new insights into molecular evolution, botanical diversity, and agricultural productivity. The power of any family or clade as a system to answer fundamental questions depends largely on the number of whole-genome sequences available, the exact branch lengths and positions of these data sets in the phylogenetic tree, and the positions of whole-genome duplications...