Abstract
Cyclobutane pyrimidine dimers (CPDs) constitute a major portion of UVB-induced DNA lesions. Cucumber plants adapt to the solar radiation by expressing CPD photolyase, which catalyzes rapid restoration of CPDs, synchronously with the UVB content of sunlight. Such an expressional pattern is attributable to light-dependent transcriptional activation of the CPD photolyase gene (CsPHR). The purpose of this research was to elucidate the molecular mechanisms underlying the light-driven transcriptional activation. Irradiation of monochromatic light revealed that UVB with wavelengths around 310 nm maximally induces the transcription of CsPHR. Furthermore, we irradiated transgenic Arabidopsis plants expressing β-glucuronidase (GUS) under the control of the 2.5-kbp CsPHR promoter and confirmed that the GUS expression was induced maximally by UVB with wavelengths around 310 nm. UVB-driven transcription of CsPHR, therefore, seemed to be mediated by a UVB-specific photoreceptor. The results of promoter deletion experiments will also be presented.
