LAUSR

Significance DNA damage causes genome instability and numerous diseases including cancers. Homologous recombination repair (HR) is an error-free pathway to repair DNA double-strand breaks, the most serious forms of DNA damage. However, the HR mechanisms in plants are still poorly understood. The transcription factor SOG1 is a master regulator of plant DNA damage responses. In this study, we find that a plant-specific ubiquitin E3 ligase DDRM1 ubiquitinates and stabilizes SOG1 to promote HR. Therefore, DDRM1- SOG1 is a plant-specific module for HR. DDRM1 is an evolutionarily ancient protein, which is identified in mosses, the first land plants, indicating that DNA damage response is an important mechanism for plant evolution from aquatic to land.