Gene Transfer to the Nucleus

The endosymbiotic evolution of mitochondrial and plastid genomes from ancestral prokaryotes is outlined stressing the net passage of genes from the organelle precursor genomes to the nucleus. We highlight recent experimental analyses of the process of nucleic acid transfer between extant organelle genomes and the nucleus. The molecular events that have accompanied functional gene transfers are described and specific cases of the relocation and nuclear expression of former organellar genes are summarised. The mechanisms underpinning gene transfer, including the movement of extant cytoplasmic organellar nucleic acids are described together with emphasis on the genetic consequences for the nuclear size and genetic complexity. We discuss the major contribution of endosymbiosis to the evolution of eukaryotes and we mention the selective forces that may be responsible for making the nucleus the preferred location for eukaryotic genes.