Perspectives Online

College researchers mine microbes for genes that may help plants in extreme environments

The "extremophile" research project is led by Grunden and Boss (standing left and right), with the assistance of (seated, from left) graduate student Yang Ju Im, undergraduate student Aaron Lomax, and graduate students Mikyoung Ji and Alice Lee.
Photo by Daniel Kim

Dr. Wendy Boss offers an elegant and artistic metaphor for a project that has stretched the boundaries of biology.

"Think of an artist's palate," says Boss. "If you have 10 colors, we've added 100 more."

The "colors" to which Boss refers are genes that allow certain microbes to survive in extreme conditions such as unusually high or low temperatures. Boss, a William Neal Reynolds Professor of Botany, and Dr. Amy Grunden, assistant professor of microbiology, have shown it is possible to take a gene from one of these microbes, known as "extremophiles," and insert the gene into a plant so that the gene continues to function.

Roughly a year ago, Boss and Grunden received a $75,000 Phase I grant from the NASA Institute for Advanced Concepts to explore the feasibility of inserting extremophile genes into plants. Based on the success of the Phase I project, Boss and Grunden were awarded Phase II funding of $400,000 to continue the project for an additional two years. Institute for Advanced Concepts grants usually go to engineering projects. Boss says the College of Agriculture and Life Sciences project was the only one involving biology approved for the grant cycle.

NASA is interested in plants that are able to withstand unusual heat, cold and other extreme conditions because extremes tend to be the norm in space and on other planets. If space travelers are to grow plants on, say, Mars, it's a good bet the plants will have to be able to bear up to extreme conditions.

Phase I of the project focused on proof of concept. Boss and Grunden wanted to prove that an extremophile gene could be inserted into a plant and that it would produce a functional protein in the plant that had the properties of the protein originally produced by the microbe. The scientists successfully transferred a gene from a microbe called Pyrococcus furiosus into special tobacco cells and into Arabidopsis, or mustard weed. P. furiosus exists in shallow and deep-sea hydrothermal vents and thrives in hot temperatures. The microbe grows optimally at 100 degrees Celsius, the temperature of boiling water.

Boss and Grunden chose for their experiments a gene called superoxide reductase. Superoxide reductase reduces superoxide, a form of reactive oxygen species produced by the microbe when it encounters stressful conditions. Reactive oxygen species are toxic and, if not eliminated rapidly, can kill a cell.

While plants produce enzymes that detoxify superoxide, the enzyme produced by the P. furiosus superoxide reductase gene does so more efficiently. Boss and Grunden were able to insert the superoxide reductase gene into model tobacco cells and into Arabidopsis, and the gene functioned; it produced the enzyme that detoxifies superoxide. Boss says the model tobacco cells she and Grunden used grow only in the lab in flasks; they will not grow into plants.

Arabidopsis, however, is another story. The scientists have produced a first generation of plants that contain the P. furiosus gene. Boss and Grunden will study these plants over the next two years to determine whether the plants benefit from the gene and how the gene affects plant growth and development.

And the scientists will move to Phase II of the project, working to move two other P. furiosus genes that function in the reactive oxygen species detoxification pathway along with genes from a cold-tolerant extremophile called Colwellia psychrerythraea into plants. These genes also help microbes endure stressful conditions by reducing both superoxide and hydrogen peroxide levels and by providing a general reducing agent that will protect cellular proteins from damage. Because the project may eventually help plants deal with stressful conditions, NASA has dubbed it "Prozac for Plants."

Of course, NASA is no stranger to the College. Since 1996, the space agency has sponsored the NASA Specialized Center of Research and Training in Gravitational Biology (NSCORT) in Plant Gravitational Biology and Genomics. Boss is among faculty members who have been active in the center, and she says conversations with other faculty members involved in the center led to ideas that were the basis for the extremophile project.

However, Boss says it was Grunden's expertise with extremophiles and willingness to work on the project that made it possible.

"Having diverse faculty helps," says Boss. "Talk is cheap. You have to have someone who is knowledgeable enough to do the research and who is interested enough to make it happen."

Grunden sees in extremophiles an "untapped resource." She points out that extreme environmental conditions are the norm for 75 percent of the earth. And microbes exist in all these environments, in the heat of deserts and the cold of sea ice and the ocean depths, not to mention deep underground.

The microbes that exist in these environments represent "a treasure trove of potential application to biotechnology," says Grunden.

While Boss is quick to give credit to Grunden for her part in moving the project forward, both scientists credit post-doctoral researchers and graduate students with playing an important role. Even undergraduates got into the act when, as part of the project, Boss and Grunden team-taught an honors undergraduate class called "Redesigning Living Organisms to Survive on Mars: Development of Virtual Plants." They plan to offer another class in Spring 2007, in which students will investigate mechanisms for reducing radiation damage in plants.

-Dave Caldwell