Mutagenesis and beyond! Tools for understanding legume biology.

The family Leguminosae is one of the largest families of flowering plants and includes important crop legumes such as soybean (Glycine max) and lentil (Lens culinaris) and forage legumes like alfalfa (Medicago sativa). Legumes vary in habit from annual to perennial and in their genomes from simple diploids to large and complex polyploids. Two legume species,Medicago truncatula and Lotus japonicus, are being used as models to study legume genetics and genomics. Both of these species belong to the Galegoid clade that includes pea (Pisum sativum) and alfalfa but is also closely related to the other agriculturally important major clade, the Phaseoloid, that includes bean (Phaseolus vulgaris). M. truncatula and L. japonicus thus represent very useful model systems to study pertinent issues that are relevant to economically vital legumes. These two species were chosen as models because of their diploid, relatively small genomes (450–550 Mb), self-fertility, relative ease of genetic transformation, and short generation time. The success of any species as a molecular genetic model depends on the availability of versatile genetic and genomic resources. The genomes of both of these species are being sequenced by international consortiums and are approaching completion (Sato et al., 2008; Young and Udvardi, 2009). In addition to the excellent transcriptomics, proteomics, metabolomics, and bioinformatics tools being developed for both species by different groups around the world, a sizeable number of mutants have been collected using various mutagenesis approaches. In this update, we will briefly describe the current mutant populations and draw particular attention to two of the most frequently used mutant resources for reverse genetics: the Tnt1-tagged population of M. truncatula and the targeting-induced local lesions in genomes (TILLING) population of L. japonicus.