August 14, 2006
Part XIII: Astrobiology
Redesigning Living Organisms for Mars
Amy Grunden and Wendy Boss
North Carolina State University
35 min. (slideshow requires QCShow Player)
Audio only (mp3 format)
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No race can prosper till it learns that there is as much dignity in tilling a field as in writing a poem.
— Booker T. Washington (1856-1915)
As planned in the current Vision for Space Exploration, humans will visit and explore Mars in the decades ahead. Inevitably, we're going to want to take plants with us, plants that will provide food, oxygen and a patch of green on an otherwise desert planet.
On Mars, plants will have to tolerate conditions that would usually cause them a great deal of stress: severe cold, drought, low air pressure, UV radiation and soils that they didn't evolve for. Oddly, there are already Earth creatures that thrive in Mars-like conditions, but they're not plants. They're some of Earth's earliest life forms — ancient microbes that live at the bottom of the ocean, or deep within Arctic ice.
The trick will be to "evolve" these plants here on Earth through genetic engineering. As explained in this week's lecture, Wendy Boss and Amy Grunden have already introduced a P. furiosus gene into Arabidopsis. Eventually, they hope to pluck genes from other extremophile microbes — genes that will enable the plants to withstand the Martian stresses.
Ordinary plants already possess a way to detoxify superoxide, but Pyrococcus furiosus uses a pathway that may work better. P. furiosus lives in a superheated vent at the bottom of the ocean, but periodically gets spewed out into cold sea water. So, unlike the detoxification pathways in plants, the ones in P. furiosus function over an astonishing 100+ degree Celsius range in temperature. That swing could match what plants would experience in Martian greenhouses.
The goal is not to develop plants that can merely survive Martian conditions. To be truly useful, the plants will need to thrive: to produce crops, to recycle wastes, and so on. "What you want in a greenhouse on Mars," says Boss, "is something that will grow and be robust in a marginal environment."
In stressful conditions, notes Grunden, plants often partially shut down. They stop growing and reproducing, and instead focus their efforts on staying alive — but nothing more. By inserting microbial genes into the plants, Boss and Grunden hope to change that.
"By using genes from other sources," explains Grunden, "you're tricking the plant, because it can't regulate those genes the way it would regulate its own. We're hoping to [short-circuit] the plant's ability to shut down its own metabolism in response to stress."
Their work has practical importance in two ways: The first is that
if Boss and Grunden are successful, stress-tolerant plants will greatly reduce the cost and complexity of the greenhouses that will need to be built on Mars.
But the second value is more immediate. Their work could make a great difference to humans living in marginal environments here on Earth. In many third-world countries, says Boss, "extending the crop a week or two when the drought comes could give you the final harvest you need to last through winter. If we could increase drought resistance, or cold tolerance, and extend the growing season, that could make a big difference in the lives of a lot of people."
"There's a treasure trove of extremophiles out there," says Grunden. "So if one doesn't work, you can just go on to the next organism that produces a slightly different variant of what you want."
— Wirt Atmar
About the Speakers
Amy Grunden
Amy Grunden completed her Ph.D. at the University of Florida in 1996. Following that graduation, Amy served as a post-doctoral research associate in the Department of Biochemistry and Molecular Biology at the University of Georgia. While at Georgia, she began working with microorganisms known as hyperthermophiles, which grow at temperatures ranging from 80C to 113C. Because of this work, she became very interested in the mechanisms and adaptations which allow these unique organisms to thrive at such high temperatures.
In July, 2000, Amy joined the faculty in the Department of Microbiology at North Carolina State University as an assistant professor and she is currently developing a research program to further investigate the physiology of hyperthermophilic microorganisms using a thermal-vent archaeon Pyrococcus furiosus as the primary research organism.
Wendy Boss
Wendy Boss is the
William Neal Reynolds Professor of Botany at the
College of Agriculture and Life Sciences at North Carolina State University.
Her research interests center around the function of inositol phospholipids in regulating plant perceptions and responses to environmental stimuli including the role of inositol lipids and calcium in graviperception and response.
In previous NASA-funded research, Wendy's team has found that 15 seconds after corn and oat plants were placed on their sides, levels of the chemical, inositol triphosphate, surged fivefold in a special part of their stems, known as the pulvinus. This chemical is also found in large amounts in the human brain and helps cells communicate with each other.
Plants will eventually need to be taken into space to provide oxygen and food. "But before we create such long-term support systems, we need to know how gravity affects the growth of plants," she's said.
Dr. Boss's primary teaching interests are those of Plant Physiology and lipid-mediated signal transduction.
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