Prokaryotes contribute more genes to eukaryotes than was thought

A study published in Trends in Genetics shows that eukaryotic organisms (those with cells that have the genetic material enclosed in the nucleus) contain genes of prokaryotic origin (organisms in which the genetic material is free within the cell) more often than previously thought. Until now it was known that prokaryotic organisms frequently include genes from other prokaryotic species through several mechanisms of horizontal transfer. The incorporation of new genes by these mechanisms had also been found in some eukaryotic organisms but these were considered as very isolated cases and it was doubted that this was a widespread mechanism. This new study, led by Toni Gabaldón from the Comparative Genomics research group of the CRG, has reviewed the DNA sequences of 60 eukaryotic species (fungi) and has found a set of genes that were rare. They then compared these infrequent genes with prokaryotic DNA sequences and confirmed that the origin of more than 700 of studied genes was often prokaryotic. Thus, this study favours the balance toward the theories that argue that the transfer of genes between prokaryotes and eukaryotes is possible and more frequent than previously thought. It also provides new clues to understand the different existing evolutionary mechanisms.