Abstract
Plants use sunlight as energy for photosynthesis; however, plant DNA is exposed to the harmful effects of ultraviolet-B (UVB) radiation in the process.UVB radiation damages nuclear, chloroplast, and mitochondrial DNA by the formation of cyclobutane pyrimidine dimers (CPDs), which are principal cause of UVB-induced growth inhibition in plants. Repair of CPDs is therefore essential for plant survival while exposed to UVB-containing sunlight. Nuclear repair of the UVB-induced CPDs by CPD photolyase is well known, but repair processes in plant chloroplasts and mitochondria are not understood.
Here, we report the photoreactivation of CPDs in chloroplast and mitochondrial DNA in rice. Biochemical and subcellular localization analyses using rice strains with different levels of CPD photolyase activity and transgenic rice strains showed that full-length CPD photolyase is encoded by a single gene, not a splice variant, and is expressed and targeted not only to nuclei but also to chloroplasts and mitochondria. The results indicate that rice may have evolved a CPD photolyase that functions in all three organelles that contain DNA to protect cells from the harmful effects of UVB radiation.
