Abstract
UVB can damage DNA by causing formation of cyclobutane pyrimidine dimmer (CPD). Photoreactivation mediated by enzyme, photolyase, is the major pathway for repairing CPD in plant, and CPD photolyase is a crucial factor for determining UVB sensitivity in plants. We previously reported that CPD photolyase functions in nuclei, chloroplasts and mitochondria in rice. This result indicates that CPD photolyase, which is encoded by a single-copy gene in the nuclear genome, translocates to chloroplasts, mitochondria, and nuclei. Thus, CPD photolyase is subjected to "triple targeting" in rice cell. Furthermore, the subcellular localization studies indicated that the C-terminus of rice CPD photolyase [385-506 amino acid regions of CPD photolyase (PHR); 385-506-PHR] contains a functional targeting signal for transport into nuclei and mitochondria. In this study, in order to the identify the nuclei and mitochondrial-targeting amino acid sequence, we constructed expression vectors encoding protein chimeras of GFP and C-terminus partial amino acid of PHR under the control of the CaMV 35S tandem promoter. We found that 385-437-PHR-GFP or 438-506-PHR-GFP was detected only in mitochondria or nuclei, respectively. According to further studies in detail, 385-403-PHR-GFP was detected in mitochondria, and three amino acids, 487-489, were functional targeting signal for transport into nuclei. In this congress, we discuss the acquired mechanisms of transport into mitochondria and nuclei in higher plants.
