Genome stability under UV-B in Arabidopsis thaliana

Ground levels of solar UV-B radiation can induce DNA damage. While mobile organisms can avoid UV-B by hiding, sessile phototrophic organisms such as vascular plants are constantly exposed to sunlight. UV-B photoreception, flavonols shielding, direct reversal of pyrimidine dimers and nucleotide excision repair are required for Arabidopsis resistance against UV-B radiation. However, the frequency of UV-B-induced mutations in wild-type plants and mutants with impaired UV-B protection is unknown. Here, we analyzed the amount and types of solar UV-B-induced mutations in the offspring of Arabidopsis wild-type and UV-B-hypersensitive mutants exposed to simulated natural UV-B over their entire life cycle. The results revealed that reversal of pyrimidine dimers by UVR2 photolyase is the major mechanism required for sustaining plant genome stability across generations under simulated natural UV-B. In addition to widespread somatic expression, germline-specific UVR2 activity occurs during late flower development, and is important for ensuring low mutation rates in both male and female sex-specific cell lineages. This allows plants maintaining genome integrity in the germlines despite constant exposure to UV-B.