GMO without GMO

You can edit DNA without introducing other people's genes

Anatoly Glossev, Vesti

Scientists have created a method of changing the genome that does not require the introduction of foreign DNA into the cell. The new technology will reduce the number of errors when editing genes. In addition, it does not fall under the restrictions imposed on GM products in some countries.

The achievement is described in a scientific article published in the journal Plant Cell Reports (Liu et al., Lipofection-mediated genome editing using DNA-free delivery of the Cas9/gRNA ribonucleoprotein into plant cells).

Safe, but forbidden

Genetically modified foods are safe to eat. This conclusion has been made in many hundreds of scientific studies. Time after time, the experimenters did not find any difference in the state of health between the experimental animals that were fed GM products and those who got regular food.

And this is not surprising. After all, biologists carefully monitor which genes they change and what consequences this leads to. This is a much more reasonable and cautious approach than mutational selection, which has been widely used for many decades with the help of radiation or chemical mutagens.

Recall that with such selection, many unpredictable mutations are initiated in the genome of an organism. And then experts check whether the plant has any useful properties by chance. It looks no more like modern technologies of spot genome editing in pre-selected places than a carpet bombing of a surgical operation.

Mutational breeding was simply lucky to appear before society was gripped by an irrational fear of the "unnatural". And decades of its successful application have convinced politicians that everything is fine with it. But the governments of many countries are still wary of much more accurate GM technologies, and the avalanche of research does not convince them of anything. For example, in Russia, the production of agricultural GM products is prohibited by Federal Law No. 358-FZ of 03.07.2016.

Not only is it possible, but it is also impossible

There is a nuance in these prohibitions. In some countries (for example, in the USA, but not in Russia), an organism is recognized as genetically modified only if DNA of another biological species has been added to its genome.

It would seem that this opens up a wide scope for activity. After all, it is not necessary to add new DNA to get new properties of the body. You can remove some of the old genes or rearrange them in places, and what happens will not formally turn out to be GMOs.

However, it was not there. To edit the genome, you need the Cas9 protein, nicknamed molecular scissors for its ability to cut the DNA molecule. An RNA guide is also required, indicating where to cut.

How to deliver this protein and RNA to the cell nucleus? Usually biologists simply inject the DNA encoding this pair into the cell. And that's it, the body already has a foreign gene (encoding the same protein and RNA). So, from the point of view of the legislator, a nightmare and horror has come, falling under the draconian regulations of GM products.

However, the introduction of Cas9-encoding DNA into the cell has a real drawback, not created by bureaucratic barriers. The fact is that DNA is quite durable. This is fraught with the fact that the Cas9 protein molecule will be synthesized repeatedly and eventually cut something wrong in the genome.

It is unlikely that this will make the product dangerous (certainly not more dangerous than the offspring of mutational selection, in which "something wrong" in the genome occurs in commodity quantities). But an unplanned mutation can affect the viability and beneficial qualities of the body.

In addition, DNA editing of human cells is already being used to treat certain diseases. And here side changes in the genes are definitely undesirable

We don't want anyone else's genomes

Now a group of biologists from the United States has found a way to introduce a ready-made Cas9 protein into the cell and guide its RNA, rather than coding their DNA. This means that from the point of view of the laws of the United States and some other countries, an organism with an edited genome will not be a GMO.

In addition, the Cas9 molecule will decompose in 3-5 days and will not be synthesized again, because there will be no genes responsible for this in the cell. This greatly reduces the likelihood that the "molecular scissors" will make unplanned changes to the genome.

"For the first time, someone came up with a method of delivering the Cas9 protein to plant cells by lipofection," says the first author of the paper, Wusheng Liu from the University of North Carolina.

Lipofection is the delivery of molecules into a cell using artificial liposomes. The liposome is a small intracellular organelle with a wall of lipids. This is a kind of bubble filled with the right substance. It can penetrate through the cell membrane and deliver its contents inside.

Lipofection is widely used in experimental medical methods. Previously, it was used to transport the Cas9 protein and the RNA directing it into mammalian cells. But no one has done this with plants yet. But the breeding of new varieties is one of the main applications of DNA editing technology.

To test their method, the authors combined Cas9 with a protein that causes fluorescent glow. They introduced this pair of proteins into the cells of ordinary tobacco. And after a few hours, the plants shone, showing that the "gene scissors" really got into the cells.

Difficulties and prospects

Of course, not everything is smooth with the new technology. It requires the removal of the rigid wall of the plant cell. From such a "naked cell" (protoplast), you can get a whole plant, but this requires careful selection of plant hormones and nutrients. Methods of growing from protoplast are known for more than 50 crops, but for the rest they have yet to be developed.

Of course, such a procedure is necessary only for the first representatives of the variety created by such a method of DNA editing. Having received several full-fledged plants, you can propagate them in the usual way.

Nevertheless, the authors are working to ensure that lipofection does not require removal of the cell wall. For example, they are testing the delivery of Cas9 to pollen cells using nanoparticles.

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