A study on expression of the gene encoding photolyase for cyclobutane pyrimidine dimer and regulation mechanism of photolyase activity

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Growth of cucumber first leaves was retarded by UV-B. It was suggested that light recovery enzyme of DNA damage was concerned with UV tolerance of plants, because the action spectrum for growth retardation was similar to the spectrum for DNA damage caused by light. Thus, I studied to elucidate control system of gene expression of a light recovery enzyme (photolyase). I isolated the cDNA, which encoded CPD-photolyase, and the genome DNA (CsPHR) from cucumber plants The level of transcript (mRNA) of CsPHR reached a maximum in the morning in the photoperiod. The peak of this morning became higher by UV-B addition.I made the action spectrum of CsPHR induction by light, and the spectrum showed the highest peak of induction around 310nm. Next, I introduced the chimera gene, GUS gene as a reporter bound to the promoter of CsPHR, into Arabidopsis. GUS was expressed in the tip of leaves, the stem and the roots when light including UV-B was irradiated to these transgenic plants. In this case too, the most prominent peak of the induction was observed around 310nm in the action spectrum for GUS induction.Synthetic derivatives of the promoter harboring a reporter gene LUC were introduced into Arabidopsis, to clarify cis domain of the promoter, and the induction of LUC by UV-B was examined. It was found that a promoter domain of 202-296bp upper stream of the translation start point was a cis domain essential for the induction. However, it was also showed that this domain alone was not possible to induce the reporter, and it was suggested that there are other factors which work cooperatively with the domain within 201bp upper stream of the translation start.