Abstract
Photoinduced lesions in DNA, namely, cyclobutane pyrimidine dimers (CPDs) and pyrimidine- (6-4) -pyrimidone photoproducts [(6-4) photoproducts], in cucumbercotyledons exposed to solar radiation in Sapporo (N 43°) Okinawa (Iriomotejima is., N 24°) quantified by enzyme-linked immunosorbent assays (ELISAs) withmonoclonal antibodies specific to each type of photolesion. The amount of (6-4) photoproducts increased with increasing dosage of solar radiation (photosyntheticphoton flux, PPF). In contrast, the relationship between the amount of CPDs and PPF was not clear, probably due to the higher activity of light-dependent repair of CPDs ascompared with that of (6-4) photoproducts. The amount of photolesions in Okinawatended to be greater than in Sapporo at the same PPF dose probably due to the difference of ozone layer thickness, suggesting the likely future effects on plants of the increased UV-B radiation that will be a consequence of depletion of the ozone layer. Changes in the amounts of DNA lesions were different between CPDs and (6-4) photoproducts. CPDs decreased in the evening, but any noticeable decrease in the amount of (6-4) photoproducts was not observed, probably resulting from the differences in light-dependent repair activities of these lesions in cucumber cotyledons.
