Type VI Retrons | RT

Zhang K, Rojas-Montero M, Poola D, et al. (2025). bioRxivPADLOCDefenseFinderDefense SystemssORFs

Type VI retrons are bacterial immune systems with a non-canonical mechanism of defense. Unlike other retrons that constitutively produce multicopy single-stranded DNA (msDNA), Type VI retrons only generate msDNA upon phage infection. The system contains a hybrid RNA (hyRNA) that combines the reverse transcription template with a translationally repressed toxic effector. Upon phage infection, the accumulation of msDNA derepresses translation of the antiviral toxin, triggering cell death and preventing phage spread. This visualization explores the genomic neighborhoods of Type VI retrons, together with other members from the same RT clade such as Type IV and Type V.