A UV-SENSITIVE MUTANT OF ARABIDOPSIS DEFECTIVE IN THE REPAIR OF PYRIMIDINE-PYRIMIDINONE(6-4) DIMERS

Plants are continually subjected to ultraviolet-B (UV-B) irradiation ( 290 to 320 nanometers) as a component of sunlight, which induces a var iety of types of damage to the plant DNA. Repair of the two major DNA photoproducts was analyzed in wild-type Arabidopsis thaliana and in a mutant derivative whose growth was sensitive to UV-B radiation. In wil d-type seedlings, repair of cyclobutane pyrimidine dimers occurred mor e slowly in the dark than in the light; repair of this photoproduct wa s not affected in the mutant. Repair, in the dark, of pyrimidine-pyrim idinone(6-4) dimers was defective in the UV-sensitive mutant.