Federal grant helps investigate plant's nitrogen-fixing properties

Thursday, October 6, 2005

DENTON (UNT), Texas -- The University of North Texas recently received $450,000 of a $560,000 National Science Foundation grant for biological research on a plant that produces its own nitrogen.

The UNT study -- which is important to agriculture, the economy and the environment -- has the potential to develop a more plentiful source of protein-rich food, decrease reliance on nitrogen fertilizers and reduce fertilizer pollution that flows from land to waterways.

UNT Associate Biology Professor Rebecca Dickstein, principal researcher for the grant, indicates the research will focus on how a symbiotic relationship between a plant in the bean family and specific bacteria allows the plant to thrive in the absence of nitrogen fertilizer. The specific plant is a legume called Medicago truncatula, and the soil bacteria are Rhizobium.

"This research has the potential to contribute to the knowledge of how legume roots and nodule cells recognize 'friend' or 'foe,' " she said.

A symbiotic relationship occurs when the plant allows the bacteria to infect it at its root system, forming a lump on the root called a nodule.

"The reason this research is so important is that the study of this type of relationship between the plant and bacteria could lead to elimination of the need for chemical nitrogen fertilizers, because it causes nitrogen to be formed in the plant," Dickstein says.

Understanding more about how the plant and bacteria react to each other could possibly allow scientists to control yield of plants.

"What we do know is that Medicago truncatula is particular," Dickstein said. "Its immune system is strong enough to ward off other bacterial infections, yet it allows Rhizobium bacteria to invade and infect its root system."

Dickstein says this infection ultimately allows the plant to produce its own nitrogen, which is important in formation of protein, nucleic acids and nerve development in humans. She says "nitrogen fixation" in Medicago truncatula is a means to get nitrogen into the food chain and provide a rich source of protein.

Dickstein says investigating how "nitrogen fixing" occurs in Medicago truncatula might make it possible to engineer the same beneficial results in plants that can't currently form their own nitrogen.

Dickstein's early findings show that Rhizobium soil bacteria enter specialized plant cells in Medicago truncatula and fix nitrogen there. She says the central research question is how Rhizobium bacteria form a nodule in the plant's root system.

"Finding and isolating genes that cause nitrogen fixation in plants could help us develop this same process in plants that don't currently have this function."

By isolating two genes in the Medicago truncatula plant, Dickstein found the plant stopped depositing nitrogen. "Going beyond initial findings, we intend to characterize and clone these two genes," she says.

A process called "map-cloning" of these genes will provide scientists with a blueprint of how the genes function as well as a possible method of transferring this benefit to other plants.

Besides the practical outcomes of the research, Dickstein's research could add to scientific knowledge about plants.

Dickstein says the research could provide an opportunity to examine important aspects of basic biology of nodule development, which had been previously difficult to study.

"We'll begin to unravel plant's mechanisms that control Rhizobial infection and deposition into the host plant cells."

The project will also offer training benefits for a number of students including a postdoctoral fellow, graduate students, Texas Academy of Mathematics and Science students and high school summer students.

This fall, Dickstein also received a $450,000 UNT Excellence fund award as a result of an internal university competition to promote research that meets the Texas Higher Education Coordinating Board definition of research and development.

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