Update on Transformation Recent Advances in Legume Transformation

Legumes are a large, diverse family ranging from herbaceous annuals to woody perennials that, because of their capacity to fix nitrogen, are essential components in natural and managed terrestrial ecosystems. Legumes have been domesticated for the production of food, feed, forage, fiber, industrial and medicinal compounds, flowers, and other end uses. Understanding the molecular basis of nitrogen fixation and the unique metabolic pathways that result in the myriad of end uses of legumes is both a matter of scientific curiosity and of economic necessity because of their importance in the biosphere and to the sustainability of the human race. In accordance, model legumes are being rapidly developed as experimental systems to pursue a number of important biological questions unique to these plants using molecular tools including genomics. A key component of most functional genomics approaches is a high-throughput transformation system useful for developing various gene identification strategies. Transformation also is emerging as an important crop improvement tool. This is particularly evident in soybean (Glycine max), in which Roundup Ready soybean cultivars have captured a major stake in market share of soybeans planted in the U.S. and Argentina. Transformation theoretically expands the sources of genes for plant improvement to all organisms, far beyond the gene pool accessible via sexual hybridization. Transformation also offers strategies for overexpressing or suppressing endogenous genes. Thus, introducing new genes or manipulating endogenous gene expression via transformation generates new phenotypic variation useful for investigating gene function and for crop improvement.