UVB‐lnduced DNA Damage and Its Photorepair in Nuclei and Chloroplasts of Spinacia oleracea L.

Abstract

ABSTRACT Ultraviolet‐B‐induced lesions and their photorepair in nuclear and chloroplast DNA of spinach ( Spinacia oleracea L.) leaves were examined with two photoproducts, cyclobutane pyrimidine dimers (CPD) and pyrimidine (6‐4) pyrimidinone photoproducts (6‐4PP). These photoproducts were induced both in nuclear and chloroplast DNA by UVB irradiation and could be detected by enzyme‐linked immunosorbent assay using their respective monoclonal antibodies. Formation of CPD was greater in nuclear DNA than in chloroplast DNA (about 10 to 7), whereas 6‐4PP formation was comparable in both DNA. On subsequent exposure of leaves to blue/UVA after UVB irradiation, photorepair of CPD and 6‐4PP occurred in nuclear DNA but not in chloroplast DNA. When isolated chloroplasts were irradiated with UVB, CPD was also induced in their DNA. But photorepair of CPD did not occur in them by subsequent exposure to blue/UVA, suggesting that no photorepair system operates in chloroplasts.