Plastid DNA in the nucleus: new genes for old.

Nuclear genomes of eukaryotes are bombarded by a continuous deluge of organellar DNA which contributes significantly to eukaryote evolution. Here, we present a new PCR-based method that allows the specific amplification of nuclear integrants of organellar DNA (norgs) by exploiting recent deletions present in organellar genome sequences. We have used this method to amplify nuclear integrants of plastid DNA (nupts) from the nuclear genomes of several Nicotiana species and to study the evolutionary forces acting upon these sequences. The role of nupts in endosymbiotic evolution and the different genetic factors influencing the time available for a chloroplastic gene to be functionally relocated in the nucleus are discussed.