Retrozymes are a unique family of non-autonomous retrotransposons with hammerhead ribozymes that propagate in plants through circular RNAs.

Our work reveals that circular RNAs with hammerhead ribozymes are frequently occurring molecules in plant and, most likely, metazoan transcriptomes, which explains the ubiquity of these genomic ribozymes and suggests a feasible source for the emergence of circular RNA plant pathogens.