Genetic engineering, indistinguishable from a normal mutation
Biologists have learned not to leave "evidence" when creating GMOs
Alexander Ershov, N+1
Biotechnologists from Korea and the USA have developed a method for making changes to the genome of a plant that are indistinguishable from those that arise during breeding. Scientists hope that the use of this method will make it possible to obtain plants with the right properties and at the same time circumvent the prohibitions that apply to genetically modified organisms in some countries. The researchers' article was published in Nature Biotechnology (Woo et al., DNA-free genome editing in plants with preassembled CRISPR-Cas9 ribonucleoproteins).
The method is, in fact, an application to plants of the well-known CRISPR technology, which was created several years ago on the basis of the bacterial antiviral immunity system. Its important feature is the use of not just genetic constructs, but ready-made RNA-protein complexes. Here, RNA acts as a "guide", which finds the only place in the genome where a mutation needs to be introduced. The protein (Cas9 nuclease) produces a double-stranded break at this point in the DNA. This gap triggers the process of homologous recombination and one or another change is made in its place.
For example, the repair system can copy a short sequence with foreign DNA introduced by scientists or a sequence from the homologous chromosome of the plant itself to the site of the rupture. Alternatively, the "treatment" of a double-strand break may result in the removal of several nucleotides and the gluing of DNA back together. However, deletions may occur during gluing, which are able to turn off this gene by shifting the reading frame. All these possibilities can be used to influence the activity of genes and, ultimately, to obtain plants with new properties.
Scientists tested the new method on tobacco, rice and the model plant Arabidopsis thaliana. Scientists have made short deletions in several genes, including a gene that inhibits the stimulator of plant immunity.
At the same time, unlike traditional bioengineering methods, no large alien structures were introduced into the genome. The changes that were observed in it are indistinguishable from ordinary mutations that occur naturally or under the influence of mutagens used in breeding. During the examination of such a plant, it will be very difficult for the state regulator to establish whether the introduction of genetic constructs into cells was used when it was obtained or whether the plant is the result of selection.
It should be noted that most GMOs currently used carry the same fragment of foreign DNA – the gene of an enzyme that provides resistance to herbicides. It is impossible to introduce this gene into the genome unnoticed, even with the help of new technology.
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26.10.2015