Abstract
The harmful effects of UVB in the sunlight are unavoidable problems for higher plants that live on photosynthesis. To keep the genomic information intact, plant cells remove the UV damage formed on the DNA by photoreactivation. Plants also have dark-repair and damage tolerance pathways to prevent growth defect caused by DNA damage. Here we report about AtREV3 and AtREV1 genes, which encode specific polymerases to bypass DNA damage. The AtREV3- or AtREV1-disrupted plants were more sensitive to UVB, γ-ray, and DNA crosslink agents than the wild type, suggesting that these REV proteins are required for plant damage tolerance. Although bacterially expressed AtREV1 protein inserted a dCMP at opposite the AP site, it failed to bypass two major UV damages in vitro. This inconsistency makes us propose a novel function of AtREV1 in the UV-tolerance pathway. To evaluate the function of AtREV3 and AtREV1 in bypassing UV-damage, we have detected replication errors that often emerged during damage bypass process. The point-mutated, non-functional uidA genes were introduced into Arabidopsis plants and reversion events (mutations) were detected by blue GUS+ sectors on the somatic tissues. We found that a disruption of AtREV3 or AtREV1 reduced the mutation frequency to 1/4 of the level of the wild type. These results suggest that the AtREV3 and AtREV1 are bypassing the DNA damage in error-prone manner.
