More than a decade ago, plant geneticists noticed something peculiar when they looked at grafted plants. Where two plants grew together, the cells of each plant showed signs of having picked up substantial amounts of DNA from the other one. In itself, that wasn’t unprecedented, because horizontal transfers of genes are not uncommon in bacteria and even in animals, fungi and plants. But in this case, the transferred DNA seemed to be the entire intact genomes of chloroplasts. This posed a conundrum, because plant cells seal themselves inside a protective cell wall that offers no obvious way for so much DNA to get in.
Now, researchers in Ralph Bock’s laboratory at the Max Planck Institute of Molecular Plant Physiology in Potsdam have finally discovered the answer by capturing this transfer on video. Not only are cell walls sometimes more porous than was thought, but plants seem to have developed a mechanism that enables whole organelles to crawl through the cell wall into adjacent cells. The researchers reported their discovery in the January 1 issue of Science Advances.
“The real novelty is that they’ve shown the actual physical organelle is moving, [and] not only from one cell to another,” said Charles Melnyk, a plant biologist who studies grafting at the Swedish University of Agricultural Sciences in Uppsala. “It’s two different plants that are exchanging organelles.” [Continue reading…]