Amborella: The Museum of Dead DNA
A new study has uncovered an unprecedented example of horizontal gene transfer — the acquisition of foreign DNA from unrelated species — in Amborella trichopoda, a South Pacific shrub that is considered to be the sole survivor of one of the two oldest lineages of flowering plants. It is the first description of a land plant acquiring genes from green algae.
Andrew J. Alverson, an assistant professor of biological sciences in the J. William Fulbright College of Arts and Sciences, performed the computational analyses that identified the many donors of this foreign DNA, which includes entire mitochondrial genomes from three green algae and one moss.
The study, led by scientists at Indiana University, included researchers from the U.S. Department of Energy, Pennsylvania State University and the Institute of Research for Development in New Caledonia.
“The Amborella mitochondrial genome is huge, and most of its DNA is foreign, acquired from the mitochondrial genomes of other plant species,” Alverson said. “We’ve never seen horizontal gene transfer at this scale. It’s not acquiring genes or bits of genes in a piecemeal way. It’s been swallowing up whole genomes. One of our main tasks was to determine the ancestry of its several hundred ‘extra’ genes.”
Most of the genes in Amborella’s extra DNA are degenerated and nonfunctional.
“Amborella is a hoarder, Alverson said. “Its genome is a museum of dead DNA.”
This large amount of “junk DNA” is evidence that mitochondrial fusion in plants is incompatible with the way mitochondrial fusion occurs in animals or fungi, Alverson said.
Pictured above: Photo by Mike Bayly, Wickimedia Commons