Plant responses to genotoxic stress are linked to an ABA/salinity signaling pathway

Cells have developed a complex network of reactions to avoid or reduce the deleterious consequences of DNA damage. Responses to genotoxic stress include activation of distinct stress signaling pathways, delay of cell cycle progression and induction of DNA repair. In contrast to other organisms, it is not known which signal transduction pathways sense genotoxic stress in plants. Here we describe an Arabidopsis mutant (uvs66) that appears to be affected in the perception of signals triggered by genotoxic treatments. The mutant uvs66 was identified as hypersensitive to UV-C and to the DNA-damaging chemicals methyl methane sulfonate (MMS) and mitomycin C (MMC), but seems to perform light dependent repair, nucleotide excision repair and homologous recombinational repair as efficiently as the wild type. Exposure of uvs66 plants to various environmental stresses revealed a normal response, with the exception of elevated salinity and abscisic acid (ABA). The hypersensitivity to NaCl and ABA is correlated with aberrant regulation of transcripts that are regulated by ABA (RAB18), or are induced by DNA damaging treatments (AtRAD51). The properties of the mutant uvs66 suggest an unexpected link between ABA and/or salt stress mediated signals and genotoxic stress responses, and provide an important connection between the physiological and genetic responses of plants to abiotic stress factors.