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Research examines potato tuber formation


May 5, 2009
By Fruit & Vegetable

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Understanding how plants produce storage organs that humans use as food would be a valuable tool for science and for a hungry world.

Understanding how plants produce storage organs that humans use as food would be a valuable tool for science and for a hungry world.

Iowa State University researcher David Hannapel, professor in horticulture, thinks he has found a key to figuring out the process.

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Hannapel studies potatoes and the process that leads to tuber formation.

Like other plants, potatoes collect sunlight in the leaves and turn that energy into sugars using carbon dioxide.

In potatoes, late in the growing season, the sugars in the leaves are delivered to underground stems during the process of making starch in the edible tubers.
“We’ve always known that there was a signal activated in the leaf that was sent down the plant to activate tuber formation,” Hannapel said. “But the identity of that signal has never been confirmed.”

Recent discoveries have demonstrated the role of a full-length mobile ribonucleic acid (RNA) molecule in a signaling system that activates tuber formation, Hannapel said.

According to Hannapel’s theory, the signal molecule RNA moves from the leaves to the tubers and communicates to the plant when to activate the pathway that leads to tuber formation. The gene that signals this activity is prompted by sunlight in the leaf. The RNA recognizes when the days are getting shorter and this induces the RNA to start moving.

Hannapel has studied tuberization for more than 20 years and knows that understanding the process takes time.

“Right now, we have more questions than answers,” he said. “But most likely RNA-binding proteins are involved that protect the RNA and deliver it to its site of function.”

Having figured out the function of the gene, Hannapel now wants to understand how the signal RNA works.

And scientific knowledge is moving fast in this area. “It was just three years ago that we discovered these RNAs were moving,” he said.

Since then, advances have been common and widespread. Scientists now know that there are hundreds of RNAs that traffic through many different plants.
“Full-length, mobile RNAs that travel long distances in plants and act as signals for development and defense are a novel idea in plant biology. The value of our work is that it provides a model for understanding how such signal RNAs are moving and what determines their final destination,” Hannapel said.

The work also has the possibility of boosting potato production.