Horizontal gene transfer: Whole chloroplasts move between species; how they do it unclear as yet – researchers
|February 2, 2012||Posted by News under horizontal gene transfer, News|
From “Genetic Information Migrates from Plant to Plant” (ScienceDaily, Feb. 1, 2012), we learn,
Plant scientists were confounded by the fact that the DNA extracted from the plants’ green chloroplasts sometimes showed the greatest similarities when related species grew in the same area. They tried to explain the phenomenon with the assumption that every once in a while those normally sexually incompatible species crossed and produced offspring with a new combination of nuclear and chloroplast genomes.
They coined the term “chloroplast capture” to illustrate what they thought was happening. Now, scientists around Ralph Bock from the Max Planck Institute of Molecular Plant Physiology in Potsdam discovered that a transfer of entire chloroplasts, or at least their genomes, can occur in contact zones between plants. Inter-species crossing is not necessary. The new chloroplast genome can even be handed down to the next generation and, thereby, give a plant with new traits. These findings are of great importance to the understanding of evolution as well as the breeding of new plant varieties.
For a long time, scientists believed that HGT was restricted to prokaryotes, organisms without nuclei. It was universally accepted that, for example, bacteria can exchange genes that are crucial to their survival, like the ones that transmit a resistance to antibiotics. Nowadays it is increasingly appreciated that HGT is in fact not restricted to prokaryotes. It can be observed at the contact zone between different animal tissues after an organ transplantation or — as shown here — between two fusing plants.
“As of now, we do not know how chloroplasts manage to get from one cell to the other,” says group leader Ralph Bock. “But the decisive point is that it happens and the discovery of this process offers a new explanation for important evolutionary processes and opens up new possibilities for plant breeders.”