Genome-enabled insights into legume biology

Legumes are the third-largest family of angiosperms, the second-most-important crop family, and a key source of biological nitrogen in agriculture. Recently, the genome sequences of Glycine max (soybean), Medicago truncatula, and Lotus japonicus were substantially completed. Comparisons among legume genomes reveal a key role for duplication, especially a whole-genome duplication event approximately 58 Mya that is shared by most agriculturally important legumes. A second and more recent genome duplication occurred only in the lineage leading to soybean. Outcomes of genome duplication, including gene fractionation and sub- and neofunctionalization, have played key roles in shaping legume genomes and in the evolution of legume-specific traits. Analysis of legume genome sequences also enables the discovery of legume-specific gene families and provides a framework for genome-wide association mapping that will target phenotypes of special importance in legumes. Translating genomic resources from sequenced species to less studied but still important "orphan" legumes will enhance prospects for world food production.