In Georgia, a forest of genetically modified trees was planted: they must save the world from the greenhouse effect

In mid-February, Living Carbon planted five thousand seedlings of genetically modified poplars in Georgia. Environmentalists and reporters are sounding the alarm as this is an unprecedented case in which a private company has received permission to grow such plants, and in record time. In addition, the company does not have scientific proof that these trees can really solve the problem for which they were created. The edition told in more detail Meduza.

Photo: IStock

The company claims that the new variety of poplar has more efficient photosynthesis, and this allows such trees to grow one and a half times faster than wild relatives. The founders of the company, who intend to plant several million such seedlings during the year, say that in this way they are going to fight an increase in the concentration of CO₂ in the atmosphere, and hence climate change.

To achieve accelerated tree growth, genetic engineers at the startup Living Carbon took advantage of the invention of synthetic biologists from the University of Illinois.

They managed to "accelerate" the rate of atmospheric carbon fixation in tobacco by introducing a pair of enzymes into the plant cells, taken in one case from the chlamydomonas algae, and in the second case from a pumpkin. As a result, tobacco actually learned to photosynthesize much more efficiently: in the experiment, the GM plant gained mass a quarter faster, and there was 40% more starch (acting as energy reserves) in its cells.

Not all plants are ideal for photosynthesis.

It is a well-known fact that plants essentially create their biomass from sunlight and air, or rather, from carbon dioxide, which, with the help of a special enzyme, turns into sugars, for which, in fact, the energy of the sun is spent. It is not so well known that not all plants carry out this process in a completely optimal way.

The fundamental problem that limits the effectiveness of carbon dioxide fixation by most plants is that the enzyme responsible for attaching the CO₂ molecule to the “preparation” of the future sugar molecule can not only attach the “correct” carbon, but also attaches the “wrong” oxygen.

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This creates a substance called glycolate, which leaves the chloroplast (where photosynthesis takes place) and eventually breaks down again to form a CO₂ molecule. It turns out that due to a mistake, instead of fixing carbon, the plant throws it away. This process is called photorespiration.

Some plants, such as corn, have learned to partially bypass this not the most efficient way of photosynthesis by using rather complex additional tricks (one way is the so-called C4 photosynthesis).

Genetic engineers from Illinois came up with a way to make the plant not throw glycolate out of the chloroplasts, but split it off inside, so that the fixing enzyme could attach this carbon to the sugar "harvest" and almost completely suppress photorespiration.

Experiments on tobacco made it possible to select a successful combination of genes for the corresponding enzymes, which the engineers from Living Carbon decided to use to optimize photosynthesis in poplar.

From a scientific article to forests with genetically modified poplars, logically, there should have been a very long way. But Living Carbon decided to cut it, the result of which can be rather doubtful.

The problem is that the trees are quite different from the tobacco plant, so the effect of the same modification on a different kind of plant can be unpredictable.

The company's researchers were also aware of this and conducted a series of experiments, the results of which were posted as a preprint on the bioRxiv website. However, at the time of obtaining permission, these data had not yet been peer-reviewed by other scientists and the article had not been officially published.

Before "releasing" the trees into their natural habitat, they were tested only in a greenhouse, where encouraging results were obtained in terms of their growth rate. But no field tests were carried out before a large-scale landing.

But that didn't miraculously stop Living Carbon from getting permission to plant trees as soon as possible. This shocked not only representatives of the Global Justice Ecology Project, an environmental organization that is fighting the planting of GM trees, but also Living Carbon's closest "competitors" - a group of scientists who have been waiting for permission for large-scale cultivation of American chestnut, resistant to the fungus, for the third year.

The founders of Living Carbon exploited a loophole in the law that avoids regulation by the federal government (USDA). The fact is that for the genetic modification of their plants, they used a rather primitive method, which formally, from a legal point of view, did not make their plants “modified”.

An amendment to agricultural legislation issued in 2020 states that only genetically modified plants that were created using a bacterial or viral vector fall under USDA regulation, that is, the carrier of new genetic information in their case is bacteria or viruses.

This is the most popular method of genetic modification in plant laboratories today. In such cases, agrobacteria, which have a natural ability to penetrate into plant cells and transfer their DNA, are supplied with a new, specially created DNA construct. It turns out that the desired gene is first introduced into the bacterium, and then the bacterium itself is added to the plant.

The same method was used by Living Carbon scientists when they conducted trial experiments on poplars. But when it came to planting a huge number of seedlings, the company, shall we say, cut corners.

She used a "gene gun" - a method of delivering DNA, which means literally bombarding plant cells with microscopic gold balls coated with genetic material. This method is also well-known and quite reliable, but its important drawback is that the desired genes, as a result of "shelling", can be integrated into an arbitrary place in the genome. Both formally and from the point of view of physiology, the plants obtained in this way are not at all the same as the seedlings that were obtained with the help of agrobacteria and for which a 50% increase in biomass was shown in the preprint compared to the original poplars.

"Climatic indulgences"

Maddie Hall is the CEO and co-founder of Living Carbon. Before that, she worked in Silicon Valley, in particular in projects such as OpenAI.

For the creation and cultivation of its poplars, the company has collected more than $36 million in venture capital and investments over the three years of its existence. But how does she expect to make a profit if poplars cannot be eaten and even their wood is not particularly valuable?

The company decided to trade "carbon credits" - quotas for greenhouse gas emissions, which are measured in tons of carbon dioxide. Living Carbon will offer companies to buy a permit to emit a certain amount of CO₂, and in return they will plant a quantity of fast-growing poplar trees that will “suck” emissions from the atmosphere in a few years.

And everything would be fine, the idea is quite good, but only on the condition that poplars really “work”, which has not yet been proven.

But there are other problems with the Living Carbon business. If we do not take into account environmental activists who call such a scheme "trading indulgences" that create only the appearance of combating climate change, then the first thing that causes concern is the possibility of "leakage" of new genes into the environment - through the crossing of GM plants with their wild options.

In addition, any improvement that allows for faster growth and avoidance of pests undoubtedly becomes an evolutionary advantage for the species, allowing it to spread faster than wild relatives and eventually crowd them out.

Environmental activists from organizations such as The Global Justice Ecology Project oppose the planting of GM trees: they believe that "improved" varieties can quickly crowd out all other trees, and thus endanger biodiversity throughout the planet. And although their point of view is also not proven, there is something to think about.

Nevertheless, the use of targeted genetic modifications to improve the properties of plants instead of traditional breeding is by itself not something new for a long time. For the US at least, about 90% of the corn, soybeans and cotton grown by U.S. farmers today are genetically engineered varieties to be resistant to pesticides and pests. In addition to these main agricultural crops and several other plant species used mainly for livestock feed, GM trees can also be found in the country - these are virus-resistant papaya and apple trees that grow apples that do not “rust” in the air.

And even genetically modified poplars have been grown in China for more than 20 years. In 2002, the Chinese Ministry of Agriculture approved two varieties of these trees for commercial use. Built into their genome are genes for bacterial insect toxins that were supposed to make plants resistant to pests. A large-scale planting of poplars in this country is carried out to combat desertification of the territory. In addition, poplar wood is used for technical purposes, such as paper and plywood.

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In 2018, Chinese scientists summed up some of the results of many years of GM poplar cultivation and research in this area. From the report, it became clear that these trees do not critically influence the structure of soil microbial communities. As for the insects that the trees are supposed to repel, it seems that there are no fewer pests in the place where the poplars grow - this may be due either to the fact that they feed on neighboring trees, or the development of resistance to the toxin, or GM trees in the wild turned out to be not as effective as in the laboratory. One way or another, at least 22 more varieties of poplars have since been bred in China, but the authorities have not yet rushed to allow them to be planted.

Scientists still have a chance to confound skeptics

The founders of Living Carbon recognize some environmental risks, so a pilot plantation in Georgia is growing GM poplars interspersed with conventional ones, which also allows for a scientific experiment that can actually be used to assess whether GM trees have the claimed properties. All GM trees are female, meaning they do not produce pollen. In addition to poplars, other species will be planted at the site to assess the impact of GM trees on biodiversity.

The owner of the farm on whose territory this unusual forest appeared has nothing against GM trees: before this, his land was not used in any way, and now, at best, he will receive rent, and at worst, a certain amount of technical wood.

Despite some opacity of the project, Living Carbon has a scientific partner - the University of Oregon. But so far, even his employees are a little skeptical about this idea. Most scientists are confused by the lack of field data, because the results obtained in a laboratory greenhouse and the results obtained in the field can be very different. The author of the development that the company used to improve the trees is also not 100% sure of success.

Apparently, so far the main “threat” posed by the new variety of poplars is unfulfilled promises. But Living Carbon has time, because while poplars are growing, engineers have years to refine imperfect technologies.

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