Transport of rice cyclobutane pyrimidine dimer photolyase into mitochondria relies on a targeting sequence located in its C‐terminal internal region

Abstract

SUMMARYThe cyclobutane pyrimidine dimer (CPD), which represents a major type of DNA damage induced by ultraviolet-B (UVB) radiation, is a principal cause of UVB-induced growth inhibition in plants. CPD photolyase is the primary enzyme for repairing CPDs and is crucial for determining the sensitivity of Oryza sativa (rice) to UVB radiation. CPD photolyase is widely distributed among species ranging from eubacteria to eukaryotes, and is classified into class I or II based on its primary structure. We previously demonstrated that rice CPD photolyase (OsPHR), which belongs to class II and is encoded by a single-copy gene, is a unique nuclear/ mitochondrial/chloroplast triple-targeting protein; however, the location and nature of the organellar targeting information contained within OsPHR are unknown. Here, the nuclear and mitochondrial targeting signal sequences of OsPHR were identified by systematic deletion analysis. The nuclear and mitochondrial targeting sequences are harbored within residues 487-489 and 391-401 in the C-terminal region of OsPHR (506 amino acid residues), respectively. The mitochondrial targeting signal represents a distinct topogenic sequence that differs structurally and functionally from classical N-terminal pre-sequences, and this region, in addition to its role in localization to the mitochondria, is essential for the proper functioning of the CPD photolyase. Furthermore, the mitochondrial targeting sequence, which is characteristic of class-II CPD photolyases, was acquired before the divergence of class-II CPD photolyases in eukaryotes. These results indicate that rice plants have evolved a CPD photolyase that functions in mitochondria to protect cells from the harmful effects of UVB radiation.

Establishment of Monitoring Methods for Autophagy in Rice Reveals Autophagic Recycling of Chloroplasts and Root Plastids during Energy Limitation

“…Although the mature leaf blade of rice is unsuitable for live-cell imaging by microscopy because of its solidness and small cell size, we recently established imaging methods using the first leaf of 5-to 7-d-old rice seedlings (Takahashi et al, 2014). In the mesophyll cells of the first leaf of mRFP-OsATG8d-expressing rice, RFP fluorescence was observed in the cytoplasm and nucleus (Fig.…”

“…For the imaging in rice leaves, first leaves of 5-to 7-d-old seedlings were used as previously described (Takahashi et al, 2014). Thin layers of around 0.5 mm were peeled from first leaves and observed by LSCM.…”

DNA damage and repair in plants – from models to crops

“…In rice nuclei and chloroplasts the photolyase is mainly present in its phosphorylated form, whereas in the mitochondria the major part of the protein is unphosphorylated. Recently, unique sequences targeting rice CPD photolyase to the mitochondria have been identified in the C-terminal region of the protein and validated as functionally important ( Takahashi et al, 2014 ). Therefore, further studies will reveal whether the access of plant photolyases to the organellar genomes is species-specific, or whether it depends on the developmental stage of the plant, as well as on the organ or tissue affected, or there are other factors at the molecular level which might control the presence and activity of plant photolyase proteins within the nuclear and extranuclear plant genomes.…”

The Gain and Loss of Cryptochrome/Photolyase Family Members during Evolution

“…The following supporting information can be downloaded at: , Supplementary Materials S1: All protein sequences_Fasta; Supplementary Materials S2: Tree of Life Table; Supplementary Materials S3 [ 165 , 166 , 167 , 168 , 169 , 170 , 171 , 172 , 173 , 174 , 175 , 176 ]: Motif table; Supplementary Materials S4: CRY/PL subfamily protein alignments; Supplementary Materials S5: Porifera alignment; Supplementary Materials S6: Phylogenetic tree (unrooted); Supplementary Materials S7: Phylogenetic tree (rooted); Supplementary Materials S8: CRY/PL distribution.…”