The Science of Sustainability

Saved From Living Death: How Genetically Modifying Chestnuts Could Bring Them Back

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We are getting very close to being able to bring back these gorgeous trees that used to dominate forests in the Eastern U.S.  Now the big question is whether we should.  Image courtesy of Wikipedia commons.

We are getting very close to being able to bring back these gorgeous trees that used to dominate forests in the Eastern U.S. Now the big question is whether we should. Image courtesy of Wikimedia commons.

Around the turn of the 20th century, the forests in the eastern U.S. were dominated by the American chestnut. These “sequoia of the east” ruled the roost back then and were the cornerstone tree species. By midcentury, though, almost all of these majestic trees had been turned into shrubs.

No, this wasn’t magic. Instead, a fungus arrived from Asia that prevented the trees from growing bigger than this. Nowadays the only tall chestnuts are a few that happened to be planted outside of the tree’s old range. And even some of these are starting to be done in.

Ever since the blight started stunting the chestnut, scientists have been looking for ways to help these trees fight back. And now they may finally be getting close to a solution. Well, actually, multiple solutions.

The one I want to focus on here is a very clever genetic modification that involves moving a wheat gene into the American chestnut. Early studies look to be very promising and these trees have even been shown to be resistant in the field. The researchers are hoping to get approval soon from the U.S. government for widespread planting.

These orange spots will eventually do this tree in.  Just like it has with most every other American chestnut.  Image courtesy of Wikimedia commons.

These orange spots will eventually do this tree in just like it has with most every other American chestnut. Image courtesy of Wikimedia commons.

The idea behind this method rests on the knowledge that the chestnut blight needs an acidic environment to do its dirty work. The way this little monster accomplishes this is by making and then pumping oxalic acid into the tree. This is incredibly damaging to the chestnut.

The obvious solution is to find a way to neutralize this oxalic acid. We are looking for a solution as simple as those old chemistry experiments where we neutralized hydrochloric acid with sodium hydroxide. This is where wheat can help.

Wheat makes an enzyme called oxalate oxidase (OxO) that breaks down oxalic acid. The researchers took the gene that has the instructions for this enzyme, the oxo gene, and put it into the chestnut tree. The tree now makes the enzyme so that it can neutralize the blight’s oxalic acid. This approach appears to be working in making the trees more blight-resistant.

When researchers looked at different trees that made different amounts of the enzyme, they found that only those that made a lot were resistant to the blight. In other words, there was a correlation between the amount of enzyme and resistance. When the gene was in the right place in the tree’s DNA, it could make a lot of enzyme so the tree could fight off the blight.

Just because we might be able to turn back time to when these trees rules, should we?  Image courtesy of Wikimedia commons.

Just because we might be able to turn back time to when these trees ruled, should we? Image courtesy of Wikimedia commons.

So now we have a GM tree that might restore these forests back to what they were a century or so ago. Now we have to decide whether to plant them or not.

This is not really an issue of the tree having been created through genetic engineering. It is very hard to come up with plausible ways that a tree with this gene could have a significant effect on the environment. The trees aren’t modified so they make their own pesticides, survive spraying by herbicides or anything like that. They simply make an enzyme from wheat that successfully battles a killer fungus by neutralizing an acid.

No, it has more to do with upsetting the new balance that has arisen over the last few decades in the forests back east. The forests have adjusted to the loss of the American chestnut and reintroducing the tree will only plunge the forests back into a period of readjustment. This temporary state of flux will be disruptive and so should be done for more than nostalgic reasons. There should be some environmental or economic benefit in bringing the American chestnut back.

Again, this discussion is not dependent on the fact that the tree is GM. The same arguments can be made for the American/Japanese/Chinese hybrids that look to be resistant too. In fact, this discussion isn’t really that different from those brought up with regards to bringing back extinct species. Like those folks in Monty Python’s The Holy Grail, the American chestnut isn’t quite dead yet, but it is close.

So we finally have ways to bring back the American chestnut. But it may be that it took us so long to find them that we don’t need them anymore. The forests have moved on, maybe we should too.

Natural range of the American chestnut as reported in 1914.  The cross hatching shows the extent of the blight back then.  Image courtesy of Wikimedia commons.

Natural range of the American chestnut as reported in 1914. The cross hatching shows the extent of the blight back then. Image courtesy of Wikimedia commons.

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Category: Biology, Blog, Environment

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Dr. Barry Starr

About the Author ()

Dr. Barry Starr is a Geneticist-in-Residence at The Tech Museum of Innovation in San Jose, CA and runs their Stanford at The Tech program. The program is part of an ongoing collaboration between the Stanford Department of Genetics and The Tech Museum of Innovation. Together these two partners created the Genetics: Technology with a Twist exhibition. Read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.
  • John Fiorentino

    I know some transgenic trees were planted last year in the Bronx, N.Y.

    I think it's a great idea!

    http://www.esf.edu/communications/view.asp?newsID=1623

    JF

    • Barry

      The most extensive plantings I know of are poplar trees in China where 1.4 million insect resistant trees were planted (the insects wouldn't let them grow before). The other big one is the papaya in Hawaii which was modified to make it resistant to a virus. Nothing bad to report with either and the poplar trees have been around for about 20 years or so.

    • John Fiorentino

      Somewhat related………………..I do want to say that foodstuffs and trees are the
      proverbial horse of a different color. As long as the technology is applied properly.

      Ben & Jerry's Will Stop Using Genetically-Modified Ingredients, Company Says

      http://www.huffingtonpost.com/2013/06/02/ben-and-jerrys-gmos-genetically-modified_n_3372451.html

  • http://geneticmaize.wordpress.com/ Anastasia

    Perhaps not every forest in the previous chestnut range needs chestnuts reintroduced, but surely there are natural and semi natural areas (such as parks) where the trees would be welcome.

  • http://twitter.com/aboutgeology Andrew Alden

    Chestnut was one of America's best lumber trees once upon a time, and also a major food source for animals and people. We *must* get it back, if only for guitar and furniture makers. The eastern US environment is already degraded from the local extinction of bison, and wolves, and the total extinction of the passenger pigeon, not to mention climate changes past and present, so the argument that the ecosystem has "adjusted" and should be left alone is specious. We are in charge of the eastern landscape now.

    • Barry

      I didn't know it was used for guitars! (I knew about lumber and food)

      • John Fiorentino

        As an old musician I can tell you Chestnut is rarely used for tonewood for a variety of reasons.

        Some have used it (mostly in Europe) on rare occasions, but the wood almost universally suffers from severe twists, making it essentially useless.

  • Benjamin Edge

    I don't believe it would be possible to reintroduce chestnuts at a rate that would be nearly as disruptive as losing them has been. Unless someone has thoughts of clearcutting and planting them in plantations, and even that would take time. It is like the author mentioned, they are not really extinct. This would be more like bringing them back from the brink.

  • http://www.thefashionablephilosopher.com The Philosopher

    I don't think it will be an issue, especially with the way they are doing it. It would probably take thousands of years for the tree to repopulate it's old native range. The only way to restore them to the way they were within our life times is to find something that could actively destroy all the blight. (they'd come roaring back) The eastern forests would be full of chestnut trees within decades (in my area the chestnut density seems to be half a dozen to a dozen an acre or so). Even then I don't think it would be much of an issue. Things have adjusted yes, but they haven't adapted to their absence.

  • labrat

    I have many questions about this approach. Common sense things like when the modified tree goes dormant or dies, how does this enzyme effect the sybiotic relationship surrounding trees have with beneficial fungi. Lets be thorough here.

    • John Fiorentino

      I believe you mean symbiotic, but am guessing that is just a typo.

      (I have been pushing the webmaster here for an edit function, so far no response)

      anyway…………..

      Unless you believe a nearby wheat field may harm "surrounding trees" in some way, I don't see what the problem might be. (Perhaps someone else has an idea?)

      And just a comment I forgot in my first post.

      I do disagree that this is similar to" bringing back extinct species." as Barry suggests. Like apples and oranges to me.

      JF