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

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.

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.

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.