The origin and impeded dissemination of the DNA phosphorothioation system in prokaryotes

Phosphorothioate (PT) modification by the dnd gene cluster is the first identified DNA backbone modification and has been shown to constitute a multifunctional epigenetic system. Despite a variety of advantages for hosting dnd systems, these systems are surprisingly distributed sporadically among contemporary microbial genomes. To address this ecological paradox, Jian et al. systematically investigated the occurrence and phylogeny of dnd systems in prokaryotes, and provided evidence to suggest that dnd systems have originated in ancient Cyanobacteria (probably Nostocales) after the Great Oxygenation Event.