QIt is often said that horizontal transfer of genes between unrelated species, which is the primary method used to create GMOs, is also found in nature. I know that natural horizontal gene transfer results in negative outcomes to the host such as pathogens

It is often said that horizontal transfer of genes between unrelated species, which is the primary method used to create GMOs, is also found in nature. I know that natural horizontal gene transfer results in negative outcomes to the host such as pathogens and galls, but what examples are there of positive outcomes ( i.e. the result of the transfer of genes is of benefit to the host) between unrelated species in nature?

AExpert Answer

Horizontal gene transfer (HGT) or lateral gene transfer (LGT) refers to transfer of genes between organisms other than through sexual or asexual reproduction (referred to as vertical gene transfer VGT). It is quite prevalent in prokaryotes and unicellular organisms but not as common in multicellular eukaryotes. As with mutation, HGT is mostly neutral and seldom negative but occasionally provides an advantage—for example, antibiotics resistance in bacteria. And in this regard, in the simpler organisms, it has played an important role in evolution. Straight infection of organisms with just the pathogenic DNA (e.g., crown gall disease) is usually not referred to as HRT if only introgression of pathogenic sequences is involved—transduction of genes from a previous host would have had to occur, and this has also been documented.

Under the endosymbiotic theory, subcellular organelles chloroplasts and mitochondria probably originated as bacterial endosymbionts of a progenitor to the eukaryotic cell. Analysis of DNA sequences suggests that horizontal gene transfer has also occurred within eukaryotes from the chloroplast and mitochondrial genomes to the nuclear genome, but, again, this is a very limited notion of HGT. The massive accumulation of sequencing data shows extensive genetic similarity among genomes of diverse organisms that are only remotely related. For example, parts of the nucleic acid sequence of a common bacterium present in our guts, E. coli, have been found in the DNA of organisms such as oilseed rape, amphibians, birds, grasses and mammals—including humans. Such findings put in doubt the value of assigning genes to a particular species and the validity of using terms such as “species-specific DNA.” And HGT is a confounding factor in inferring phylogenetic trees based on the sequence of single genes.

Posted on January 31, 2018
Thank you for your question. There are various aspects of your question. I assume your question refers to the use of Agrobacterium rhizogenes by scientists to intentionally transfer genes from the bacterium to plants. Infection and DNA transfer from this bacterium occurs in nature all the time to cause disease. Such transformed plants are not classified as GMOs since transfer occurred naturally. If this is done by scientists then it would be classified as a GMO. Rules and... Read More
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Posted on March 1, 2018
I’m a Monsanto scientist who has more than 20 years of experience with genetic modification of plants. I will try to answer your question, even though I don’t ever do experiments on animals, certainly not on humans, of course! Can humans be genetically modified…but a much bigger question is should humans be genetically modified? There are two ways to think about genetic modification of humans (or any animal). One way is modification of somatic cells, and the other is the... Read More
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Posted on May 10, 2017
The simple answer is that 20+ years of composition assessments of GMO crops have demonstrated that crop composition is not appreciably affected by the GM process (1). In addition, data collected through that time have indicated that general factors such as the growth environment can contribute to notable variation in component levels (2). Plant agglutinins (or lectins) and amylase inhibitors are examples of anti-nutritional compounds that may be present in crops. The relevance of such a... Read More