TLS polymerases and DNA-damage tolerance in higher plants

Sakamoto, Ayako; Yoshihara, Ryohei; Narumi, Issei

For the purpose of generating valuable agricultural products, various types of ionizing radiations have been applied to plants. However, molecular mechanism(s) of mutagenesis in higher plants are not yet fully understood yet. In order to understand the plant DNA repair and mutagenesis, we first isolated mutants that showed altered resistance to UV-light by in Arabidopsis thaliana. By analyzing a mutant plant that showed reduced root growth after UVB exposure, we found that specific DNA polymerases, TLS polymerases, are important for plant UV tolerance. These are AtPol, AtRev1 and AtPol thought to bypass the UV-induced damage. By exposing AtPol- or AtRev1-knockout plants to ray or MMC, their root growth was inhibited, indicating that AtPol and AtRev1 are also required to tolerate other DNA-damaging agents besides UV. We next analyzed mutation frequencies in UV or -ray treated plants. The elimination of AtPol- or AtRev1 reduced the UV-induced mutation frequency to 1/4 of the level of wild type, while the elimination of AtPol enhanced the frequency more than twice. By contrast, a significant change in -ray induced mutation frequency was observed only in AtRev1-knockout plants but not in others.. These results suggest that TLS polymerases have an important role(s) in DNA-damage tolerance in higher plants.