title: UV-B light induces an adaptive response to UV-C exposure via photoreactivation activity in Euglena gracilis.
abstract: Phytoplankton such as Euglena are constantly exposed to solar light which is used for photosynthesis. Although the solar ultraviolet (UV) induces DNA damage such as cyclobutane-pyrimidine dimers (CPDs), many kinds of living organisms can repair CPDs by photoreactivation (PR) utilizing the near-UV/blue light component in sunlight. Euglena cells are known to possess such PR activity. In the present paper, the formation of CPDs induced by UV-C exposure and the photoreactivation PR repair of these CPDs by UV-A are demonstrated. To clarify the adaptive responses prior UV-B irradiation on PR activity, cells were cultured in the dark or under UV-B light. When the cells were cultured in the dark for 3 d prior to UV-C exposure, PR activity decreased. When the cells were cultured under UV-B light, however, PR activity increased. These results suggest that exposing the cells to UV-B prior to exposure to UV-C induced an adaptive response towards DNA damage caused by UV-C exposure, and this UV-C induced damage was repaired through PR activity.
authors: Department of Biology, Nara Medical University School of Medicine, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan.
authors: Akihisa
authors: A
authors: Takahashi
authors: Naoaki
authors: N
authors: Shibata
authors: Shoko
authors: S
authors: Nishikawa
authors: Ken
authors: K
authors: Ohnishi
authors: Noriaki
authors: N
authors: Ishioka
authors: Takeo
authors: T
authors: Ohnishi