Wavelength dependency of the light-driven transcriptional activation of the cucumber CPD photolyase gene

UVB radiation (280 nm similar to 315 nm) is known to retard plant growth. DNA lesions are thought to be largely responsible for the growth inhibition due to UVB. Cyclobutane pyrimidine dimers (CPDs) constitute a major portion of UVB-induced DNA lesions. CPD-specific DNA photolyase (CPD photolyase) rapidly restores CPDs, rendering plants tolerant to UVB. We previously showed that the photolyase activity in cucumber leaves rises in the midst of the day when the solar UVB is intense, and that such diurnal fluctuation of the photolyase activity is attributable principally to light-dependent transcriptional activation of the CPD photolyase gene (CsPHR). In the present research, we examined the accumulation of the CsPHR transcripts under monochromatic light and showed that the CsPHR transcription is maximally induced by UVB with wavelengths around 310nm. It was surmised that the transcriptional activation is mediated by an unidentified UVB-specific photoreceptor.