Abstract
Phylogenomic approaches have shown that eukaryotes acquire genes via gene transfer. However, there are two fundamental problems for most of these analyses; only transfers from prokaryotes are analyzed and the screening procedures applied assume that gene transfer is rare for eukaryotes. Directed studies of the impact of gene transfer on diverse eukaryotic lineages produce a much more complex picture. Many gene families are affected by multiple transfer events from prokaryotes to eukaryotes, and transfers between eukaryotic lineages are routinely detected. This suggests that the assumptions applied in traditional phylogenomic approaches are too naïve and result in many false negatives. This issue was recently addressed by identifying and analyzing the evolutionary history of 49 patchily distributed proteins shared between Dictyostelium and bacteria. The vast majority of these gene families showed strong indications of gene transfers, both between and within the three domains of life. However, only one of these was previously reported as a gene transfer candidate using a traditional phylogenomic approach. This clearly illustrates that more realistic assumptions are urgently needed in genome-wide studies of eukaryotic gene transfer.