Plant mutation could produce super tap roots

UC Berkeley and Carnegie Institution scientists at Stanford have found a mutation in plants that makes the tap root accumulate large amounts of oils, proteins, and starch-a discovery that could lead to genetically engineered plants that store commercially useful substances in an enlarged root.

The finding could make possible the creation of more nutritious root crops with a better balance of oil, protein, and starch. Most root crops in the Third World, such as cassava and taro, are a source of starch only and often a poor source. When eaten as a dietary staple they can lead to deficiency diseases.

The mutation, called pickle because it creates a root that looks like a pickle, was discovered independently by two teams in the experimental plant Arabadopsis thaliana, a member of the mustard family commonly used for genetic experiments. The mutation makes it grow into a much enlarged root like a carrot, rich in starch, oil, and protein. This mimics what happens in seeds, which typically accumulate and store proteins and oils, making them nutritionally superior to root crops like turnips and sweet potatoes.

Once the teams find and clone the gene involved in the mutation, scientists will be able to track down the analogous gene in other plants. Eventually they should be able to engineer plants that store oils or proteins in an enlarged tap root. Z. Renee Sung, professor of plant and microbial biology, leads the Berkeley team.

The Carnegie team has already created plants with seeds containing a type of plastic, and other plants whose seeds contain a precursor of nylon.

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