Early Transfer of DNA from Insects to Pines
Whole genome DNA sequencing is the key technology in studying the evolution of gene structure and function. Such efforts will be instrumental in guiding breeding programs needed to face the growing food, feedstocks and fiber demands of the 21st century. Forest Service scientists at the agency’s Southern Research Station recently sequenced the genome of loblolly pine, and used this data to delve further into the pine genome's details. They found that a group of repetitive DNA sequences had been transferred from insects to a common ancestor of the pines, spruces, and other conifers, about 340 million years ago, but not to any other trees. The sequences are known as Penelope-like transposable elements, or Dryad elements. Further analysis from 1,928 genomes of 14 major lineages showed that there was no evidence of the Dryad elements outside of animals and conifers. Transposable elements can be thought of as genomic parasites, because once they invade a genome they become highly active at making new copies of themselves resulting in marked increases in the species' DNA content. Most organisms have genetic mechanisms to reject foreign DNA or shut down the multiplication activity of the foreign sequences; however, in the case of a newly evolving species, where the defense mechanism has not fully developed, the foreign DNA can make hundreds of thousands of copies that can persist in the host species' genome for millions of years. In these cases, the foreign DNA is likely to cause structural changes to their host genomes that can affect the function of nearby genes. The Dryad elements likely had significant influence in the genomes of ancestral conifers and could still be influencing the genome of present day conifers, such as loblolly pine. Nonetheless, future research is needed to understand how conifer chromosomes and genes are affected by these DNA sequences since their presence is an important indicator of past and future evolution.
|An ancient trans-kingdom horizontal transfer of Penelope -like retroelements from arthropods to conifers||(publication)|