Arabidopsis in space

When the space shuttles Discovery and Atlantis blasted off in the direction of the International Space Station (ISS) this year, passengers of a more botanical variety vastly outnumbered the seven astronauts on board. Secured in small seed cassettes, some 1600 seeds of the cress species, Arabidopsis thaliana, took the flight for a research project designed to help tease out the tropic influences of gravity and light on plant growth, while perhaps helping to find a way to grow crops for long missions to the Moon and Mars.

A. thaliana, of course, is "the lab rat of plant biology," explains project leader John Kiss of Miami University. The little species has been rigorously studied over the years, its genome sliced and diced into databases, and its growth patterns described in detail.

At least, that's the case under earth's regular gravitational conditions. How it might behave in microgravity is less certain. That's why Kiss and his colleagues, with funding from NASA and the assistance of the European Space Agency, designed a series of experiments that will take place over coming months on board the ISS.

He sent 560 seeds up on Discovery in July and the balance (1,120 seeds) on Atlantis in September. "The big thing that we're interested in is the interaction between light and gravity in plant development," says Kiss. "If you're a plant, these two signals are vital for all aspects of growth and development. But on Earth it's impossible to study a pure phototropic effect."

On the space station, European astronaut Thomas Reiter will be responsible for the experiment, although most of it will take place automatically. The seed cassettes containing the cress seeds will be grown in a 655-pound incubator, called the European Modular Cultivation System (EMCS), which allows researchers to control atmosphere, lighting, and humidity of growth chambers.

Once safely transferred to the space station, the seedlings will be grown under red or blue light, under microgravitational conditions, and compared with controls growing in a centrifuge to simulate earth's gravity. Scientists hope the experiments will shed some light on gene-activation patterns in response to the different stimuli. "There are all these genes involved in light regulatory pathways in plants, but you're never sure whether these genes are activated in response to light or a combination of light and gravity," Kiss says. The experiments also offer a rare chance to examine the weak phototropic responses in root systems.

Beyond giving botanists a better understanding of plant genetics, the research also has a purpose that's more down to earth, so to speak. By adding to NASA's growing knowledge of how crop plants might behave in low gravity, they will help space agencies develop ways to grow food away from Earth's atmosphere.

The capacity to grow crops will become vital for possible future long-term missions, Kiss explains. As his colleague Roger Hangarter from Indiana University said in a statement: "If we are going to send human flights to Mars, we can only do that if they grow their own food."

During the course of the experiments, Kiss and his colleagues were planning to monitor events courtesy of regular video downloads, and conference calls with Reiter. After growing for seven days, the seedlings will be frozen at -80ﾰ C and returned to earth.

At that point, the data analysis will begin in earnest. Plant germination, growth, and curvature will be analyzed from the videotapes, and DNA analysis will be conducted on the frozen plant samples to determine how the different light and gravity treatments affect gene expression.

In the meantime, Kiss is quite happy to keep conducting space science from Earth. He had done several similar experiments in the past, and he has no desire to blast off himself in the name of science. Says Kiss, "I always enjoy interacting with the astronauts, they're pretty interesting folks."