WEST DANBY, Tompkins County — Scientists at the College of Environmental Science and Forestry in Syracuse are leading an effort to save the American chestnut from devastating blight using genetic engineering — also known as GE. They have inserted wheat genes that produce the enzyme oxalate oxidase, into chestnut tree cells. Trees grown from those cells are able to break down oxalic acid, which the chestnut blight fungus ordinarily uses to invade chestnut tissues and kill the trees. This alteration enables the GE trees to tolerate chestnut blight infections, whereas the trunks of wild American chestnut trees are nearly always killed.
This seems like a good thing. Why would anyone oppose it?
My objections start with the genetic engineering process itself. In contrast to the image that GE proponents promote, genetic engineering is not a precise technology. Packets of genetic material are inserted randomly into the host genome, disrupting any DNA in the vicinity. Because of this, the vast majority of GE “events” (instances where genetic material is successfully incorporated) harm the organism and often are fatal.
The few cells that live are cultured and tested to see whether they express the desired traits, then grown into baby trees via tissue culture. However, because of the genetic damage inflicted by the method, many of these grow poorly or have undesirable traits. Those that make the cut are grown on — but the key point is that these still carry genetic disruptions. They are simply less visible.
Studies on GE corn and soybeans show that often multiple copies of genes are inserted at various locations, often containing much more than the desired DNA. To understand the full significance of this it is necessary to appreciate that the inserted packet of DNA includes not only the gene of interest but also multiple other sequences of DNA that regulate and promote the production of the desired new chemical within the plant. Non-functional copies of parts of that packet, along with other DNA debris, often wind up strewn through the chromosomes. Thus, the genome of the host plant is degraded. If traits are stacked with multiple events, this is further compounded. The damaged DNA could have functions that are lost but don’t show right away, such as resistance to other diseases or those allowing for positive interactions with mycorrhizal fungi, etc. These damages could result in undesirable effects when the GE trees eventually grow in the forest environment, effects that were not apparent during initial tree selection.
A clear alternative is to pursue a conventional breeding program. This will attain all of the goals of the GE program, without the introduction of degraded DNA to the wild populations. This work is already well underway by the American Chestnut Foundation, which sadly supports the GE approach as well.
Another problem is the motivation behind this project. Why use genetic engineering when conventional breeding is making good progress on similar blight tolerant trees? In fact, conventional breeding with multiple resistances is likely to be much more stable than using an inserted gene. An objection to the conventional approach is that it uses Chinese and Japanese chestnuts as sources of blight resistance, incorporated into crosses with American chestnut trees. Some people evidently feel that trees from such crosses are less “purely American.”
It is important to note that all chestnut species are thought to have evolved from a common ancestor, so they share a very high percentage of identical DNA. Some descendants evolved resistance to chestnut blight, and can freely cross with the others which lack it. After several backcrosses, 95+ percent of the DNA in a seedling is from the American parents, which is mostly identical to that of the Asian parents anyway. It is hard to see how such a seedling is meaningfully less “pure” than one of the degraded GE plants.
The Syracuse researchers soon will be requesting approval to plant hundreds of GE chestnuts in the wild, so they will cross with remaining wild trees and spread their DNA. Once this happens, it cannot be called back. By focusing on the American chestnut as a first GE tree release into the wild, the way will be paved for releases of other, less beloved species. Approval for release into the wild — based on a misguided desire to save the American chestnut — will make it much easier to gain approval for other GE trees whose motivation will be strictly financial. Industrial plantings of pine and eucalyptus trees are widespread, and GE versions of these and others would quickly follow. The history of GE agricultural crops shows clearly that their use is based on profit and market control, not on human or environmental values.
Future steps in the adoption of genetically engineered organisms, of course, point toward human engineering. If it is OK to alter plants and animals all around us, why not ourselves? Engineering humans, now underway in some labs, raises very disturbing prospects of oppression and exploitation. GE chestnuts are one more step along the way. If that is a future you don’t desire, it is much easier to stop now than it will be after many incremental GE approvals.