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GUY RAZ, host:

We're back with ALL THINGS CONSIDERED from NPR News. I'm Guy Raz.

A few days ago, I was on the edge of the Potomac River in Maryland, coating my pants with insect repellent.

Mr. JOHN KRESS (Botanist, Smithsonian Institution): Stay off, bugs.

RAZ: I was following John Kress - he's a botanist at the Smithsonian Institution - through a dense forest of tulip poplars, maple trees and spice bush. We were on our way to an obscure little island just a few miles upstream from Washington, D.C. It's called Plummers Island, and it's the place where the quest to sequence the DNA of every single plant species on earth began.

Mr. KRESS: Sorry, a little overgrown.

RAZ: After about 15 minutes, we stop at the edge of the Potomac. The water is low, and the channel separating the mainland from Plummers Island is just a few feet wide. So John Kress leads the way as we scamper over some rocks and onto the island.

Mr. KRESS: So here we are at the welcome to Plummers Island sign, the most thoroughly studied island in North America.

RAZ: And that is a fact?

Mr. KRESS: That is a fact.

RAZ: This is the most thoroughly studied island in North America.

Mr. KRESS: There's been more biologists out here looking at everything from worms to flowers to birds to mammals to snails than any other spot on the East Coast.

RAZ: All on these 12 acres.

Mr. KRESS: All on these 12 acres.

RAZ: It's a strange little island: peaceful, serene, isolated. And yet, it sits directly under the flight path from Dulles Airport and right below the busy Capital Beltway. John Kress comes here at least once a month.

Now, much of his research on plant life has taken him to more exotic places like Burma and Ecuador, places with far more biodiversity than Plummers Island. But it's here, on this tiny little patch of land in Maryland, where a microclimate creates an unusual environment.

Mr. KRESS: You think of the temperate zone, the mid-Atlantic forest with oaks and maples and things. Right where we're standing right now, we're surrounded by tropical plants. The papaws are in the tropical family Annonaceae. The spicebush is in the tropical family, the Lauraceae or the Laurels. And so when I look in here, I feel like I'm in Costa Rica sometimes because it's just the sorts of things I'd see if I was in a lowland tropical forest in Central America.

Of course, the big trees are not really tropical. They're the oaks, they're the maples, they're the walnuts. But when I'm here, particularly in the heat of the summer, it really feels like the tropics.

RAZ: Are these native to this area?

Mr. KRESS: Yeah. Yeah, they're native.

RAZ: Yeah?

Mr. KRESS: In fact, the papaws are probably also fruiting right now. We might find some papaw fruits around.

RAZ: Can you eat it?

Mr. KRESS: You can eat it. They're good.

RAZ: Kress leads me up a narrow path to the highest point on the island. At the top sits an old ramshackle wood cabin.

(Soundbite of door opening)

RAZ: The cabin is the clubhouse for a super-exclusive fraternity called the Washington Biologists Field Club. It's been around for about 100 years, and membership is strictly limited. There are only 65 spots. And even with his distinguished record of research, John Kress didn't get in until 10 years ago.

Mr. KRESS: As members pass on, we have new members, younger members.

RAZ: So you can't expand.

Mr. KRESS: We can never expand it.

RAZ: So in order to become a member, somebody has to pass away.

Mr. KRESS: That's - or leave the area and resign their membership, which is rare.

RAZ: So this has got to be one of the toughest clubs in the city to get into.

Mr. KRESS: I'm probably not going to comment on that.

RAZ: The members are the stewards of the island. They actually owned it until a few years ago, when they donated it to the federal government.

Outside the cabin, Kress fills me in on a project that could potentially revolutionize the way we understand plants.

Mr. KRESS: What we were doing on Plummers Island was using it as a pilot study for something we want to take to the tropics and take to forests all around the world, which is developing a system of identification based upon the DNA of a species. This DNA marker we call a DNA bar code. And that's essentially taking a small segment of DNA that we can find in all organisms. We have to locate it on a certain part of the genome, but it's variable enough that it's different for all species on the planet. And then we can take any sort of part of a plant or take a hair or a leg of a grasshopper, grind it up, get out the DNA, sequence this little chunk of DNA and then tell what species that is.

RAZ: The bar code he's talking about isn't a literal bar code like a UPC symbol on a cereal box. It's a code that's inside the plant.

Mr. KRESS: The DNA is inside the trees…

RAZ: I see.

Mr. KRESS: …inside the plants. And we extract that DNA, and then we have to sequence that DNA to actually identify the plant.

So that's - we're not there yet in terms of me picking a leaf off the ground and telling you immediately from its DNA bar code what that is. We would have to take it back to the lab…

RAZ: Right.

Mr. KRESS: …sequence it. But technology is heading in the direction where we expect what now sits on top of a desk as a DNA sequencer will eventually fit in the palm of your hand.

RAZ: So like an iPhone or something?

Mr. KRESS: Like an iPhone, cell phone.

RAZ: Within a few years, John Kress imagines kids wandering through forests around the world with portable scanners that could analyze a sample of any plant, check it against the DNA database he's creating, and know within a few seconds what species they're looking at. But to get closer to that future, we have to get off the island and into the lab.

(Soundbite of car starting)

RAZ: So we drive about 30 minutes to Suitland, Maryland, home of the Smithsonian Museum Support Center. It's a giant campus where the Smithsonian stores all the stuff you don't see in the museums. And it also hosts dozens of research labs.

Mr. KRESS: The affectionate name for the museum support center is The Death Star.

RAZ: The scientists call it The Death Star because it's one of the cleanest places you've ever seen - spotless.

Unidentified Woman: Okay. Everybody sign in. I just need a photo ID.

RAZ: We're here to meet Kress' partner in the DNA barcoding project. His name's Dave Erickson. Dave is the guy who collects all the plant samples sent to him from around the world, including the samples collected on Plummers Island.

Mr. DAVE ERICKSON (Botanist, Smithsonian Institution): And we take literally two hole punches out, and that's the source of all the DNA that we'll use.

RAZ: Two hole punches.

Mr. ERICKSON: Two hole punches. And that is more than enough DNA to do all the sequencing we're going to use. In fact, it's so much DNA that we can preserve that for whole genome sequencing down the future if we get to that.

RAZ: Once the samples come in, Erickson grinds them up and sends them to a DNA extractor.

(Soundbite of machine)

RAZ: Eventually, the plant's DNA is analyzed and the data from the specific gene is converted into the DNA bar code. And that bar code is what goes into the DNA database at the center.

Mr. ERICKSON: Anybody who wants to go to Plummers Island or, in theory, as we extend this to all plants, anywhere, collect a plant in any kind of forensic context that the technology for extracting the DNA and sequencing that is ubiquitous.

So let's say there's a kid in the hospital. He's sick, he barfs up some stuff. They can recover that fragment of leaf tissue that he ate, do a DNA extraction. Because we have a reference library at this defined set of genes, they know exactly what gene I need to target and sequence. Once they do that, they can figure out what this kid ate.

RAZ: Hmm.

Mr. ERICKSON: Okay? So the power of the reference library is that it's the same gene. Everybody knows what it is. It's easy to recover in a lot of different environments and contexts.

RAZ: Similar plant species might have very important differences, like one strain might be poisonous and one might not be. Right now, when scientists need to distinguish between two different species of plants, plants that might appear identical to the naked eye, they have to wait until those plants produce fruits or flowers, and that could take up to half a year.

Back on Plummers Island, John Kress says that future when people will know instantly what plant they're looking at is still a bit far away. There are literally millions of plant species to sequence, and thousands more yet to be discovered. But at least here, on these 12 acres in the middle of the Potomac, the job is complete.

Mr. KRESS: It's pretty amazing to walk through here and know that we have a DNA bar code for every plant that's out here.

RAZ: Every single thing.

Mr. KRESS: Everything.

RAZ: If you'd like to see photos of Plummers Island and the lab at the Smithsonian's Support Center, visit our Web site at npr.org.

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