An intron endonuclease facilitates interference competition between co-infecting viruses

Abstract

Introns containing homing endonucleases are widespread in nature and have long been assumed to be selfish elements that provide no benefit to the host organism. These genetic elements are common in viruses, but whether they confer a selective advantage is unclear. Here we studied an intron-encoded homing endonuclease in bacteriophage ΦPA3 and found that it contributes to viral competition by interfering with the replication of a co-infecting phage, ΦKZ. We show that gp210 targets a specific sequence in ΦKZ, which prevents the assembly of progeny viruses. This work demonstrates how a homing endonuclease can be deployed to engage in interference competition among viruses and provide a relative fitness advantage. Given the ubiquity of homing endonucleases, this selective advantage likely has widespread evolutionary implications in diverse plasmid and viral competition as well as virus-host interactions.

Summary

A homing endonuclease provides a relative fitness advantage during viral competition.