Perspectives Online

Seeds in Space. Transgenic tomatoes from N.C. State travel to the International Space Station. By Dave Caldwell

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When the Space Shuttle Endeavor rose from its Florida launch pad in early August, it carried passengers from N.C. State University. "We're sending up tomato plants," said Dr. Chris Brown, professor of plant biology in the College of Agriculture and Life Sciences.

Actually, tomato seeds traveled into space on the shuttle, destined for the International Space Station.

Once the seeds that traveled on the space shuttle reached the space station, they were planted in growth chambers designed for the challenges of the space environment.
Photo by Becky Kirkland
"These are transgenic tomato plants that are modified such that the signaling pathway related to how they respond to gravity was altered," Brown explained. At the time of the launch, Brown was director of space programs for the Kenan Institute for Engineering, Technology and Science at N.C. State. He also directed the N.C. Space Grant program. He has since assumed new duties as the university's Assistant Vice Chancellor for Research Development. He will continue to direct the N.C. Space Grant program.

On the space station, the seeds would be "planted," inserted into growth chambers specifically designed for the challenges of the space environment, and then they'd grow. Similar seeds were planted back on Earth, and scientists will compare the growth of the space plants with that of the Earth plants.

Brown said pictures of the space tomatoes would be down-linked back to Earth, where they'd be analyzed and be made available on a Web site designed at N.C. State to teach elementary and middle school students about space and foster interest in science.

The tomato seeds that rode the shuttle were developed by Dr. Mariya Khodakovskaya, a post-doctoral researcher in the laboratory of Dr. Heike Sederoff, assistant professor of plant biology.

Sederoff studies how plants respond to gravity. The tomatoes that went into space were altered genetically so that they have less of a substance called inositol triphosphate, or IP3. Brown described IP3 as "an important signaling molecule in the gravity response" of plants.

In effect, IP3 helps tell the plant which way is up so that its roots can grow down. The transgenic tomatoes have less IP3, so their gravity response should be less robust than normal tomatoes. Couple that with free fall, or microgravity conditions in space, and there could be some interesting results. IP3 may also affect drought tolerance, Brown added. The transgenic tomatoes are extremely drought tolerant, their leaves are thicker than normal, and the tomatoes contain more lycopene, an antioxidant.

Dr. Mariya Khodakovskaya (top, left) developed the genetically altered tomato seeds. Directly above are the tomato seeds in their space station habitat.
Top Photo by Becky Kirkland
Bottom photo Courtesy Heike Sederoff
Brown said the plants would grow in chambers designed by Bio-Serve Space Technologies, a non-profit NASA-sponsored Research Partnership Center at the University of Colorado at Boulder. The growth chambers contain a semi-solid nutrient solution, and the plants will grow for as long as the solution provides moisture.

Speaking shortly after the launch, Sederoff said a first batch of seeds was scheduled to be planted on the space station Aug. 29. Seeds were to be planted at the University of Colorado at the same time, while two days later, on Sept. 1, Sederoff planted seeds in her laboratory. The Earth-bound tomatoes would be grown in the same type of chambers used on the space station.

The tomatoes that were sent into space are a miniature variety called Micro-Tom, Sederoff said. The plants produce tomatoes the size of a quarter or smaller. Sederoff said four different lines of Micro-Tom tomatoes were sent into space: a wild-type line, two lines that were genetically transformed to produce less IP3 and a fourth control line that was genetically altered, but the alteration does not affect IP3 production.

Sederoff said the plants would be allowed to grow for about six weeks, and then another batch would be planted.

She added that genetic transformation of tomatoes to produce less IP3 is a continuation of work begun by Dr. Wendy Boss, William Neal Reynolds Professor of plant biology, and Dr. Imara Perera, senior researcher in plant biology, several years ago. Perera transformed Arabidopsis plants to alter IP3 production.

Brown did not anticipate the plants would grow long enough to produce tomatoes. But he added, "We'll see. I would be surprised if they produced tomatoes, but who knows. It's space."

Sederoff was more sanguine; she thought the plants might produce fruit."We would love to see some fruit," she said.

Dr. Heike Sederoff (top) and Khodakovskaya will compare these plants grown on Earth to the space-grown plants. The Micro-Tom variety (bottom) produces tomatoes the size of a quarter or smaller. Four different lines of Micro-Toms were sent into space.
Top Photo By Becky Kirkland
Bottom Photo Courtesy of Heike Sederoff
The experiment is, in Brown's words, "observational," and designed to a certain extent to test the Bio-Serve plant-growing system.

"We would like to see, number one, that the plants and the plant-growing system are successful, that the plant-growing system and our transgenic plants work together," Brown said. "Second, we'd like to see if there are any differences in the growth in space that we can discern from growth here on the ground."

Being able to grow plants in space would likely be a vitally important piece of human long-term space travel or colonization. As Brown pointed out, plants are "the ultimate life support machine for long-term human application" in space.

Plants, he explained, produce oxygen and take up CO2. They can clean water by taking up dirty water through their roots and transpiring clean water vapor through their leaves. Plants also produce food and may be used as building materials.

And, said Brown, "Plants are nature's best chemists," producing secondary chemicals, such as pharmaceuticals or neutraceuticals.

On Earth, plants respond to gravity; the roots automatically grow downward. In the minimal gravity of space, there effectively is no down. So if astronauts are to take plants into space with them, it is imperative that scientists understand how plants respond to gravity.

And if scientists understand how plants respond to gravity, it may be possible to alter them genetically so they are better adapted to life in space. That is what the researchers are working to do. CALS has had a strong space biology program since 1996, when a NASA Specialized Center of Research and Training in Gravitational Biology in Plant Gravitational Biology and Genomics was located in the College.