Post-genomics studies of developmental processes in legume seeds.

Legume seeds are an important source of food and feed, and have been principally studied with a view to optimizing the composition of reserve substances starch, oligosaccharides, oil, and protein. The availability of genome and transcribed genome sequences for the legume model species Medicago truncatula and Lotus japonicus has stimulated the application of the -omics technologies to understanding legume seed development in these and closely related crop species. The -omics techniques that we shall consider here are transcriptomics, proteomics, metabolomics, and ionomics (Fig. 1). Transcriptomics and proteomics methodologies attempt to describe the global complement of transcripts and proteins, respectively, of an organism, and utilize directly primary genomic sequence or expressed sequence tag information as reference. In contrast, metabolomics analyses determine organic metabolite constitution, and ionomics the inorganic ion contents of the organism. They are thus distinct but complementary sources of information about different levels of the phenome. The full exploitation of -omics depends on the establishment of interactive databases that facilitate connecting these different sources of information obtained without any a priori knowledge (Dondrup et al., 2009; Truncatulix: http://lily.cebitec. uni-bielefeld.de/truncatulix/app; Henckel et al., 2009; Legoo: http://www.legoo.org/). This backbone of technology is being applied to legume seeds in a number of ways: to dissect gene expression at different levels of detail (whole seed, component tissues, organelles, etc.), to study different physiological phenomena such as the different phases of seed development, maturation and germination, or biotic and abiotic stresses, and to evaluate the effects of specific mutations on phenotypes.