Horizontal gene transfer (History)

Bacterial genetics starts in 1946

1946. The possibility of horizontal gene transfer was first realized from study of bacterial genetics 1946, when Lederberg and Tatum discover genetic conjugation in Escherichia coli K-12

1959. Tomoichiro Akiba and Kunitaro Ochia discovered the first interspecies gene transfer, mobile antibiotic resistance genes in bacteria .

1969. James Shapiro characterizes the first mobile gene DNA, transposons, as spontaneously occurring insertions of large inserts of extra DNA that caused mutations in the galactose genes of the bacterium Escherichia coli .

see main article Horizontal gene transfer in prokaryotes

First glimpses of horizontal transfer of traits in plant evolution

1940. The historical concept of a genome as a stable structure that is faithfully inherited from generation to generation has tended to cause the biological importance of horizontal gene transfer to be overlooked. The earliest glimpses that eukaryotic genomes were indeed dynamic structures was obtained by Barbara McClintock in the 1940s at Cold Spring Harbor Laboratories, New York. Her work led to recognition of transposons and other mobile DNAs in plants, which besides being able to move between different locations within a genome, also move between different species. By 1963 the parallels between McClintock's discoveries in maize and genetic instability in bacteria were clearly recognized , but her work was not fully appreciated until mobile DNA and horizontal gene transfer in bacteria was thoroughly studied in the 1960s and 70s

1971. Horizontal gene transfer is suggested as an explanation for the fact that similar traits are often shared by unrelated flowering plants, particularly by those sharing the same ecosystems, and for shared traits carried by plants and endophytic fungi that grow on their surfaces.

2003. It was shown that there is widespread horizontal transfer of mitochondrial genes among flowering plants.

Discovery of mobile genes in flies, and mariner

1970. In February of 1970 wild male fruit-flies from Harbingen, Texas, were discovered to have a second X sex chromosome (dubbed the MR chromosome) that was inherited in an unusual way, and it also was noticed that this MR chromosome participated on genetic recombination, which does not normally occur in male fruit-flies.

1970s. Mobile DNA in flies. This discovery of strange genetics in Drosophila immediately generated interest among geneticists, and during the 1970s, this and similar genetic instabilities of the fruit-fly were intensively investigated. By 1977 is was possible for M. Green to point out that the MR chromosome contained mobile genes (P-elements) that were similar to well characterized mobile DNA of bacteria (for instance Insertion sequences (IS) and mutator bacteriophage Mu). Mobile DNA from the MR chromosome had been found to move to new chromosomal locations and promote chromosomal aberrations analogous to bacterial mobile DNA.

1980s. By the early 1980s, Margaret Kidwell and others had already well documented the horizontal movement of mobile P genes in fruit fly populations , and the existence of horizontal gene transfer in insects, and the similarity of insect P mobile genes to bacterial mobile genes such as IS that have major natural roles in horizontal gene transfer in bacteria, was firmly established and widely known. More generally, Horizontal gene transfer is widely accepted as significant contributor to natural evolution in many species.

1983. Hugh Robertson reported the widespread but patchy distribution of mariner mobile DNA in insects, and by 1999 Robertson and others had reported close relatives of this mobile DNA in mites, flatworms, hydras, insects, nematodes, mammals and humans.

2000. Subsequent to these discoveries horizontal gene movement has interested a wider audience. Horizontal gene transfer is called by some (Gogarten, 2000) "A New Paradigm for Biology " and emphasized by others as an important factor in "The Hidden Hazards of Genetic Engineering". "While horizontal gene transfer is well-known among bacteria, it is only within the past 10 years that its occurrence has become recognized among higher plants and animals. The scope for horizontal gene transfer is essentially the entire biosphere, with bacteria and viruses serving both as intermediaries for gene trafficking and as reservoirs for gene multiplication and recombination (the process of making new combinations of genetic material)." .

HGT and genetic engineering

1975-present.Genetic engineering itself involves frequent use of artificial horizontal gene transfer. Molecular cloning technologies (genetic engineering) were developed in the 1970s using plasmids, the entities involved in much natural horizontal gene transfer from microorganisms, as tools to carry foreign DNA inserts in bacteria, and through use of plasmids as genetic engineering vectors biologists became acquainted with the concept that mammalian genes could function in bacteria, and that bacterial proteins could function in eukaryotes. Mobile DNA such as transposons is now widely used in in vivo genetic engineering in both bacteria and multicellular organs, but was pioneered by John Beckwith, David Botstein, Nancy Kleckner and John Roth in the 1960s-70s with bacteria.