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MU researchers find cause of tassel-less corn to be boron deficiency

MU researchers recently used a piece of tassel-less corn to study boron’s effect on plant cells.

Sept. 2, 2014

Living in Columbia, where one is never far from a farm, it is easy to take advantage of the complexity of agriculture.

Paula McSteen, an associate professor of biological sciences, and a team of researchers have been working to understand boron’s role in agriculture.

Their research began with a mutant corn plant, which had no tassels, the pollen-producing flowers. McSteen became interested in which gene caused the mutation because it is important for producing tassels and improving the size of corn ears.

Kim Phillips, a graduate student at Penn State University, mapped the genome of the corn plant and found the gene responsible for the mutation.

“(In genetics,) you actually don’t know what you’re going to end up with,” McSteen said. “We had no idea we were working on boron. We didn’t start off to look for boron. We just were interested in how tassels are made.”

Collaborating with professors from other departments and universities, including Simon Malcomber from California State University-Long Beach, the team discovered the tassel-less gene appeared to be a boron transporter.

According to MU post doctoral student Amanda Durbak, who was the first author of the project’s research paper, they tested their hypothesis that the gene produced a boron transporter by injecting RNA into unfertilized frog eggs. The team also collaborated with MU plant sciences professor Walter Gassman and MU research specialist Sharon Pike to test their hypothesis.

After being injected with the RNA, the egg produced the boron transporters. When placed in a boron solution, the eggs swelled due to the intake of boron, and some even burst.

“When it swells for a while, (the membrane) can just stretch out, but if it’s too quick it can’t do that, it bursts,” Gassman said.

For more information on boron, the team turned to emeritus professor of plant sciences Dale Blevins and biochemist Malcolm O’Neill from the University of Georgia.

Boron plays an important role in plants, especially in the cell wall. Through a process called cross-linking, boron affects pectin to help make cell walls more stable. It is a delicate balance, McSteen said, because too little boron can cause the cell to collapse in on itself due to instability, while too much makes the cell wall overly rigid.

Meristems, or stem cells of a plant, are particularly vulnerable to boron imbalance. Plants’ meristems continue functioning throughout their life, unlike the stem cells of humans. However, the researchers found that it was most important to keep a healthy balance of boron while the corn was producing tassels and ears.

“That’s kind of one of the tricky parts: How much is the sweet spot?” Durbak said.

The team took their research to the corn fields and found that a little boron goes a long way. Durbak found that the fields watered with a boron fertilizer grew normally, while those given only water had difficulties growing in Missouri’s naturally boron-deficient soil.

Farmers can put the study to use right away by getting the boron levels of their soil tested.

“Straightaway, all farmers should be testing if they have boron-deficiency and adding boron if they need to,” McSteen said. “If they added more boron (at the correct times), they would get more yield.”

However, McSteen said, boron research has plenty of future potential as well. Currently, she is collaborating with the chemistry department to develop methods of visualizing boron in cells.

“That involves sticking our plants into the nuclear reactor here,” McSteen said. “So, that’s kind of cool.”

As time passes, more and more applications of the team’s basic research may be found.

“That’s why basic research is so important because you never know how it’s going to be important in the future,” McSteen said.

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