The extent is amazing:
Using a new experimental setup, the researchers were able to observe structural changes in the cell walls in the wound tissue of the graft site. “The cell walls formed protrusions, creating junctions between the two partners. The size of those created pores allows the migration of an entire plastid. Therefore, the genome does not migrate freely, but encapsulated from cell to cell,” Hertle continues. However, to actually make this possible, the plastids have to shrink and become mobile. These rod-shaped plastids are equal to an amoeba and grow back to normal size after transfer into the target tissue.
The researchers have thus uncovered a new pathway for intercellular exchange of very large cell structures, which may also be used by parasitic plants, such as mistletoe, to carry out gene exchange with their host. In addition, it now needs to be clarified whether mitochondria and the nuclear genome also use similar transfer mechanisms.
The transfer of genetic material occurs quite frequently in plants. This can either result in a new combination of the genetic material, or alternatively the recipient cell can establish both genetic variants in parallel. This union of two different genomes, called allopolyploidization, is very interesting in evolutionary terms, as it leads to the formation of new plant species and is widespread in many plant groups. Many important crops, such as bread and durum wheat, oats, cotton, canola, coffee, and tobacco have such combined genomes from at least two crossed species.
Max-Planck-Gesellschaft, “How different plants can share their genetic material with each other” at ScienceDaily
The paper is open access.
See also: Horizontal gene transfer: Sorry, Darwin, it’s not your evolution any more