Genetic analysis of DNA-damage tolerance pathways in Arabidopsis

Key message Genetic analysis revealed a two-branch DNA-damage tolerance mechanism in Arabidopsis , namely translesion DNA synthesis and error-free lesion bypass, represented by Rev3 and Rad5a-Uev1C/D, respectively. Abstract DNA-damage tolerance (DDT) is a mechanism by which cells complete replication in the presence of replication-blocking lesions. In budding yeast, DDT is achieved through Rad6–Rad18-mediated monoubiquitination of proliferating cell nuclear antigen (PCNA), which promotes translesion DNA synthesis (TLS) and is followed by Ubc13-Mms2-Rad5 mediated K63-linked PCNA polyubiquitination that promotes error-free lesion bypass. Arabidopsis and other known plant genomes contain all of the above homologous genes except RAD18 , and whether plants possess an intact DDT mechanism is unclear. In this study, we created Arabidopsis UEV1 (homologous to yeast MMS2 ) gene mutations and obtained two sets of double mutant lines Atuev1ab and Atuev1cd . It turned out that the Atuev1cd , but not the Atuev1ab mutant, was sensitive to DNA damage. Genetic analyses revealed that AtUEV1C/D and AtRAD5a function in the same pathway, while TLS represented by AtREV3 functions in a separate pathway in response to replication-blocking lesions. Furthermore, unlike budding yeast RAD5 that also functions in the TLS pathway, AtRAD5a is not required for TLS. Observations in this study collectively establish a two-branch DDT model in plants with similarity to and difference from the yeast DDT.