Spotlight: Mysteries of Nature’s Most Versatile Legume Revealed

Spotlight: Mysteries of Nature’s Most Versatile Legume Revealed

Date Published:
Tuesday, August 3, 2010

Among the many plants that humans have found useful enough to domesticate, soybean (Glycine max) is a wonder. Like other legumes, it has the important ability to make some of its own essential nutrients by hosting nitrogen-fixing bacteria. Soybean is also a virtual chemical factory, so rich in proteins that it is a major source of protein for animal feed, and so rich in oils that it is used to produce much of the world’s cooking oil; it is also a major source for biodiesel.

If it seems as if nature could hardly have made agriculture a more useful plant, at last we may be able to understand why. The first complete sequencing of the soybean genome has now made available the fine details of the soybean’s productive genetic code and is revealing an unusual evolutionary history that led to its chemical versatility.

Since most plants with histories of genome duplication lose many of their extra gene copies relatively quickly, a major question remaining is why the soybean has not dumped its extras.

The sequencing of the soybean genome was announced in a paper in the January issue of the journal Nature. Authored by Jeremy Schmutz of the Joint Genome Institute and the HudsonAlpha Genome Sequencing Center and researchers from 18 institutions, including UNC Charlotte, the paper details results pointing to key evolutionary events that may be responsible for the plant’s unusual capabilities.

Since most plants with histories of genome duplication lose many of their extra gene copies relatively quickly, a major question remaining is why the soybean has not dumped its extras. UNC Charlotte’s Jessica Schlueter, assistant professor, points out that the oldest identified occurrence of polyploidy in the soybean lineage occurred 59 million years ago, a time near the point where legume family itself first emerged, and the event may be related to the development of these plants’ shared ability to form the unique adaptation of root nodules that house nitrogen-fixing bacteria.

The nodules are a particularly valuable evolutionary development, since they give legumes the ability to produce their own biologically usable form of nitrogen, an element that is essential for biological processes (especially protein production) but is also frequently scarce in a usable form. Developing a feature that allowed a biological partnership with nitrogen-fixing bacteria was a game-changer for the legumes.

If soybean may have kept its duplicated genes because it was able to diversify many of them into new genes that gave the organism useful new capabilities, the question is what were those new capabilities, and how are they related to the plant’s diverse chemical attributes that humans find so useful? Finding out is the complicated task ahead for Schlueter’s research.