| Co-Investigator(Kenkyū-buntansha) |
NAGATO Yasuo Graduate School of Agricultural and Life Sciences, Professor, 大学院・農学生命科学研究科, 教授 (10143413)
IKEHASHI Hiroshi Kyoto Univ.Agric., Professor, 農学部, 教授 (50193222)
HATTORI Kazumi Nagoya Univ.Agric., Professor, 農学部, 教授 (40023494)
MIKAMI Tetsuo Hokkaido Univ.Agric., Professor, 農学部, 教授 (50133715)
SANO Yoshio Hokkaido Univ.Agric., Professor, 農学部, 教授 (70109528)
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| Research Abstract |
Many findings for new breeding sciences were reported. One of the important findings was the stability of plant mitochondrial genome. Mitochondrial sequence that contains the chloroplast-derived trnH gene has been highly conserved in the region around one terminus of the junction between chloroplast-derived and mitochondrion-specific sequences in most of the gramineous plant analyzed. The results of RT-PCR, northern hybridization, in vitro capping and ribonuclease protection experiments show that the chloroplast-derived trnH gene is transcribed from a promoter that is located in the mitochondrion-specific sequence. Gene expression in this region seems to be correlated with the conservation of the sequence at the junction between chloroplast-derived fragment and the mitochondrion-specific sequence.
Thus, expression of chloroplast-derived tRNA genes is important for the stability of plant mitochondrial genome. Previous investigations located nine of the genes for rice tRNAs on chloroplast-derived sequences in mitochondrial DNA.We examined whether these genes were also transcribed in the rice mitochondria. Northern blot hybridization revealed that seven of these genes (trnC, trnF, trnH, trnM, trnN, trnS and trnW) are transcribed and are precisely processed to mature tRNAs. One of the other two genes (trnP) is transcribed but cannot be processed efficiently, and the other (trnR), which has 100% identity to the original plastid tRNA_<Arg> gene, is not transcribed in rice mitochondria. These results suggest that seven of the nine pt-derived tRNAs may be utilized for biosynthesis of protein in plant mitochondria, and support for the stability of plant mitochondrial genome.
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