There is a lot of bad publicity around genetic engineering, especially when it comes to the genetic modification of plants and animals. Most opponents of genetic engineering claim that inserting foreign genes into other organism’s genome is unnatural and dangerous. Genetic engineering might hold some risks and needs to be regulated, but it is certainly not unnatural. Many organisms have been doing it for a long time without any cataclysmic consequences, although scientists rather call these events horizontal gene transfer than genetic engineering.
The most simple, sophisticated and widespread genetic engineers on Earth are viruses. Many of them have the ability of inserting their genome into the genome of different hosts as well as the ability to “steal” genes from one species and insert it to another species’ genome. Viruses are a major driving force of evolution and there would be no Homo sapiens without viral genetic manipulations of our ancestors’ genomes (to understand what I mean, read Frank Ryan’s book Virolution.
Bacteria are also exchanging genes between each-other using gene cassettes. This exchange is for example responsible for the quick spread of antibiotics resistance in pathogenic bacteria. Other bacteria, such as the plant pathogen Agrobacterium tumefaciens, are able to transfer part of their genetic material (so-called T-DNA) into the host plant’s genome to manipulate its defense mechanisms and metabolism. Researchers discovered this natural mechanism a while ago and are using Agrobacteria to insert selected genes into plant genomes. A recent study has shown that Agrobacterium T-DNA sequence is naturally present in sweet potato and some of its wild relatives. Technically, this makes sweet potato a ‘natural GMO’ and the Agrobacterium a crop genetic engineer. Human genetic engineers use these bacteria and their natural mechanism of gene transfer to produce transgenic plants.
Some people would still argue that bacteria have no nervous system and therefore their actions cannot be regarded as engineering. That does make sense, but certainly the next example covered brilliantly by The Atlantic is harder to dismiss. Briefly, the parasitic wasps from the Braconidae family use “domesticated” viruses (bracoviruses) encoded in their genomes in order to suppress the immune system and parasitize their hosts, butterfly caterpillars. These viruses are domesticated because the viral particles only enclose genes for virulence factors and lack those needed for replication. The wasps produce viral particles in their ovaries and inject them aside with eggs into caterpillar victims. The really striking part of the story is that these viruses were also found in genomes of some victims, for example in the silk moth and the monarch butterfly. This means that in the evolutionary past some of the wasp’s victims survived the egg parasitism and have also integrated the supplied bracovirus genes into their own genome. The wasps thus probably unknowingly became “genetic engineers”. As another twist, these viruses were also “domesticated” by the butterflies’ genomes where they took another function – to fight off the infection with other viruses, the deadly baculoviruses.
In the end, we must admit that “genetic engineering” is not something that our species has invented, we merely discovered the mechanisms other organisms are using and now we try to use them in our favor.
By Marko Petek, PhD, BioSistemika, LLC