Distribution, Sequence Homology, and Homing of Group I Introns among T-even-like Bacteriophages EVIDENCE FOR RECENT TRANSFER OF OLD INTRONS

摘要: Self-splicing group I introns are being found in an increasing number of bacteriophages. Most contain open reading frame coding for a homing endo-nuclease that confers mobility to both the intron and endonuclease gene (HEG). The frequent occurrence intron/HEG has raised questions whether spread via horizontal transfer between phage populations. We have determined complete sequences known among T-even-like bacteriophages together with intron-containing genes td, nrdB, nrdD from phages without introns. A previously uncharacterized isolate, U5, is shown all three introns, only besides T4 "full set" these Sequence analysis td nrdB intronless provides evidence recent transmission occurred phages. fact several HEGs suffered deletions rendering them non-functional implies endonucleases no selective advantage rapidly degenerating probably dependent upon transmissions maintenance within Several can home closely related during mixed infections. However, efficiency varies on homology regions flanking insertion site. optional respective strongly affect homing. These findings give further insight into mechanisms propagation evolution