Acquisition of an Archaea-like ribonuclease H domain by plant L1 retrotransposons supports modular evolution

Transposons are jumping genes that constitute a sizeable fraction of eukaryotic genomes. They drive genome evolution and can cause genetic diseases and cancer. Although transposons were first discovered in plants and much of our knowledge about them stems from plants, the most abundant human transposon, L1, has barely been investigated in plants. In this study, we identify plant L1 retrotransposons from a variety of plant genomes and show that, similar to viruses, they evolved in a modular fashion by gaining and losing various protein-coding domains. Moreover, we find that plant L1s carry an active Archaea-like ribonuclease H (RNH) domain, suggesting that they shuttle RNH between plants, bacteria, and Archaea.