Adaptation for horizontal transfer in a homing endonuclease.
Selfish genes of no function other than self-propagation are susceptible to degeneration if they become fixed in a population, and regular transfer to new species may be the only means for their long-term persistence. To test this idea we surveyed 24 species of yeast for VDE, a nuclear, intein-associated homing endonuclease gene (HEG) originally discovered in Saccharomyces cerevisiae. Phylogenetic analyses show that horizontal transmission has been a regular occurrence in its evolutionary history. Moreover, VDE appears to be specifically adapted for horizontal transmission. Its 31-bp recognition sequence is an unusually well-conserved region in an unusually well-conserved gene. In addition, the nine nucleotide sites most critical for homing are also unusually well conserved. Such adaptation for horizontal transmission presumably arose as a consequence of selection, both among HEGs at different locations in the genome and among variants at the same location. The frequency of horizontal transmission must therefore be a key feature constraining the distribution and abundance of these genes.
Koufopanou
Vassiliki
V
Department of Biology, Imperial College, Silwood Park, Ascot, Berkshire, UK. v.koufopanou@ic.ac.uk
Goddard
Matthew R
MR
Burt
Austin
A
D017124:Conserved Sequence; D004271:DNA, Fungal / Q000235:genetics; D004706:Endodeoxyribonucleases / Q000235:genetics*; D022761:Gene Transfer, Horizontal / Q000235:genetics*; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D006180:Proton-Translocating ATPases; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics
D004271:DNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D004706:Endodeoxyribonucleases; D006180:Proton-Translocating ATPases; C081687:VMA1 protein, S cerevisiae